Instruction Manual November 2005
OCM III
open channel
© Siemens Milltronics Process Instruments Inc. 2005
Safety Guidelines: Warning notices must be observed to ensure personal safety as well as that of
others, and to protect the product and the connected equipment. These warning notices are
accompanied by a clarification of the level of caution to be observed.
Qualified Personnel: This device/system may only be set up and operated in conjunction with this
manual. Qualified personnel are only authorized to install and operate this equipment in accordance with
established safety practices and standards.
Unit Repair and Excluded Liability:
• The user is responsible for all changes and repairs made to the device by the user or the user’s
agent.
• All new components are to be provided by Siemens Milltronics Process Instruments Inc.
• Restrict repair to faulty components only.
• Do not reuse faulty components.
Warning: This product can only function properly and safely if it is correctly transported, stored,
installed, set up, operated, and maintained.
Note: Always use product in accordance with specifications.
Copyright Siemens Milltronics Process
Instruments Inc. 2005. All Rights Reserved Disclaimer of Liability
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manual for agreement with the
instrumentation described, variations
remain possible. Thus we cannot
guarantee full agreement. The contents of
this manual are regularly reviewed and
corrections are included in subsequent
editions. We welcome all suggestions for
improvement.
Technical data subject to change.
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TABLE OF CONTENTS
TITLE PAGE
ABOUT THIS ...
About This Manual 7
About the OCM-3 7
SPECIFICATIONS 9
Programmer 10
Transducer 11
Temperature Sensor 11
Cabling 11
Communication Software 11
INSTALLATION
Installing the OCM-3 13
Outline and Mounting 13
OCM-3 Layout 14
System Diagram 15
Installing the Transducer 16
Installing the Temperature Sensor 16
mA Output 17
Relays 17
Synchronization 18
Power Connections 19
Installing the Memory Back-up Battery 20
Communicating Via Computer 20
Installing the Programmer 20
7ML19985AB01 OCM III 3
START UP
General 21
Keypad 21
Legend 22
Initial Start Up 22
Fundamental Checks 25
OPERATION
Memory 27
Security 27
Units 27
Flow Calculation 28
Display 28
Damping 29
Relays 30
mA Output 30
Fail-Safe 31
Flow rate and Totalizing 31
Logging 32
Blanking 34
Temperature 34
Time and Date 34
Emulation Mode 35
Reset 35
Flow Velocity Input 36
Auxiliary Head Input 36
DC Output 37
Diagnostic Aids 37
7ML19985AB01 OCM III 4
‘D’ PARAMETER LISTING 39
‘F’ PARAMETER LISTING 41
‘P’ PARAMETER LISTING 43
‘U’ PARAMETERS FOR P3 PRIMARY ELEMENT 51
Simple Exponential Devices, P3 = 0 53
BS-3680 Rectangular Flume, P3 = 1 58
BS-3680 Round Nose Horizontal Crest Weir, P3 = 2 60
BS-3680 Trapezoidal Flume, P3 = 3 62
BS-3680 U - Flume, P3 = 4 64
BS-3680 Finite Crest Weir, P3 = 5 66
BS-3680 Thin Plate Rectangular Weir, P3 = 6 68
BS-3680 Thin Plate V-Notch Weir, P3 = 7 70
Rectangular Weir (Contracted), P3 = 8 72
Round Pipe, P3 = 9 74
Palmer-Bowlus Flume, P3 = 10 76
H - Flume, P3 = 11 78
Universal Head vs. Flow, P3 =12 80
Rectangular Area x Velocity, P3 = 13 82
Trapezoidal Area x Velocity, P3 =14 84
Modified Trapezoidal Area x Velocity, P3 = 15 86
U Channel Area x Velocity, P3 = 16 88
Circular Area x Velocity, P3 = 17 90
Gull-Wing Area x Velocity, P3 = 18 92
Egg-Shaped Area x Velocity, P3 =19 94
Universal Area x Velocity, P3 = 20 96
APPENDICES
Maintenance 99
Error Codes 100
Communications 101
7ML19985AB01 OCM III 5
7ML19985AB01 OCM III 6
ABOUT THIS ...
ABOUT THIS MANUAL
Although the OCM-3 is very ‘approachable’ due its dialogue capabilities and intuitive
operation, the user should be familiar with this manual. This manual provides the user
with the necessary information required to install, start up and operate the OCM-3.
As the OCM-3 prompts the user with specific messages in a step-by-step fashion
during programming, the Start Up section serves essentially to compliment the
OCM-3. Start Up provides the user with instructions on the use of the programmer
and an overview of the programming requirements.
The ‘D’, ‘F’, ‘P’ and ‘U’ parameters listed in the Parameters section provide a quick
reference of the available programming and display parameters and their options. The
‘U’ parameter listing also provides mathematical and graphical details as a reference
to assist the user in programming the OCM-3 to the primary element being used. The
user is urged to rely on the manufacturer’s specification for obtaining and identifying
the primary element to which the OCM-3 is being applied.
In short,
If you want to know about
Read
the product About This . . .
Specifications
getting started Installation
Start Up
how it works Operation
Parameters
Appendices
ABOUT THE OCM-3
The OCM-3 is to be used only in the manner
outlined in this instruction manual.
The Milltronics OCM-3, Open Channel Meter, is an electronic instrument designed to
measure flow in open channels. It is housed in a polycarbonate enclosure and comes
with a removable programmer. As a system, it is used in conjunction with a remote
ultrasonic transducer (or auxiliary head measurement device) and a temperature
sensor.
The OCM-3 transmits a pulse signal to the transducer which is then emitted as
ultrasonic pulses. The pulses echo off the water surface and are then sensed by the
transducer. The time for a pulse to echo back from the water surface is temperature
compensated and converted into a measurement of head.
7ML19985AB01 OCM III 7
The OCM-3 converts the head measurement into flow rate, but also provides a
velocity sensor input for applications where a flow velocity measurement is required to
perform the flow calculation. The flow rate is totalized and stored in a comprehensive
data log to provide detailed flow analysis.
Programming of the OCM-3 allows the operator to select the flow calculation specific
to the primary measuring device (flume, weir or pipe). Special emphasis has been
placed on providing the most accurate flow calculations possible. To this end, specific
routines have been written to comply with the British Standards Institute’s
Specifications BS-3680. These routines calculate correction factors taking into
account second order effects such as approach velocity and boundary layer. In the
event that flow measurement is not covered by one of the flow calculations provided,
the OCM-3 can be programmed for flow measurement using one of the universal
flow calculations.
The OCM-3 provides serial communication for remote programming, data log retrieval
and print out for devices such as computers, PLCs and printers. Milltronics provides a
standard utilities software package for OCM-3 programming, remote display and data
retrieval. However, the user is not limited to the software provided. The user can
develop his own software program to perform tasks suited to his specific needs.
The OCM-3 features:
✓ multi field illuminated LCD, for ‘Flow and Total’ and ‘Relay Status’ display
✓ 0 or 4 to 20 mA output
✓ three multipurpose relays, including remote totalization
✓ 1 to 24 months data log, subject to logging rate
✓ extensive serial communication, including RS-232
✓ removable infra-red programmer
✓ AC and DC (bi-current) operation.
7ML19985AB01 OCM III 8
SPECIFICATIONS
Power: » dc supply: » 9 to 30 V DC, 8 W max
and / or
» ac supply: » 100/115/200/230 V ac ± 15%, 50/60 Hz,
20 VA max
Environmental: » location » indoor /outdoor
» altitude: » 2000 m max
» ambient temperature » – 20 to 50 °C (–5 to 122 °F)
» relative humidity » suitable for outdoor (Type 4X/Nema 4X
IP65 enclosure)
» installation category » II
» pollution degree » 4
Memory
back-up: » 3 V lithium battery (NEDA 5003LC or equivalent)
» operating life 1 year
» ‘SuperCap’ capacitor for back-up
during battery replacement
Range: » 0.3 m min to 1.2 m max ( 1 to 4 ft)
0.6 m min to 3 m max (2 to 10 ft)
Resolution: » 0.2 mm (0.007")
Accuracy: » ±1 mm/m, calculated error less than 0.02%
Temperature
Compensation: » external sensor to compensate over
the operating range
Programming: » via supplied programmer and
communication link
Inputs: » velocity sensor and
auxiliary head » range: » 0 to 10 V dc
» resolution: » 2.7 mV
Outputs: » transducer drive: » 44 Khz, 400 Vpp pulses of 0.1 msec typical
duration at a 100 msec typical repetition rate.
» instrumentation: » range: 0-20 or 4-20 mA
» resolution: 5 uA
» maximum loading: 1 KΩ
7ML19985AB01 OCM III 9
» isolation: 300 V ac continuous
» relays: » 3 alarm/control relays
» 1 form ’C’ SPDT contact per relay, rated at
5 A at 250 V ac non-inductive or 30 V dc
» dc output: » +24 V dc
» 20 mA average to 200 mA at 1/10 duty
cycle max
Communication: » RS-232 or ± 20 mA bipolar current loop,300,
600, 1200, 2400, 4800, 9600 or 19200 baud
Data Logs: » variable rate on 1, 5, 15, 30 or 60 min or 24 hr
» 31 days minimum/2 years maximum
Display: » illuminated liquid crystal 5 x 7 dot matrix
display with 2 lines of 40 characters each
Enclosure: »Type 4X / NEMA 4X / IP65
» 209 mm W x 285 mm H x 92 mm D
(8.2" W x 11.2" H x 3.6" D)
» polycarbonate
Weight: » 2.3 Kg (5.1 lb)
Approvals: » CE *, FM, CSA NRTL/C
» MCERTS Class 1 open channel flow device with environment
operation limits at 35 °C (95 °F) at 93% relative humidity
SIRA MC 050058/01
PROGRAMMER
Enclosure: » general purpose
» 67 mm W x 100 mm H x 25 mm D
(2.6" W x 4" H x 1" D)
» ABS plastic
Operating Temperature: » –20 to 50 °C (–5 to 122 °F)
7ML19985AB01 OCM III 10
Battery: » 9 V (ANSI / NEDA 1604, PP3 or equivalent) or
3V lithium battery
TRANSDUCER
Model: » XRS-5*
Refer to associated Transducer manual.
TEMPERATURE SENSOR
Model: » TS-2, LTS-1 or LTS-1C
Refer to associated Temperature Sensor manual.
CABLING
Transducer: » RG-62U coaxial
» maximum separation 183 m (600 ft)
» must be run in grounded metal conduit
mA Output: » Belden 8760 or equivalent
Synchronisation: » Belden 8760
Temperature Sensor: » Belden 8760, 1 pair shielded/twisted,
18 AWG or equivalent
» maximum separation 183 m (600 ft)
» can be run in conduit with transducer cable
Communication: » RS-232: » Belden 8770, 3 wire shielded, 24 AWG
or equivalent
» maximum separation 15 m (50 ft)
» Bipolar Current: » Belden 9552, 2 pair shielded/twisted,
18 AWG or equivalent
» maximum separation 1,500 m (5,000 ft)
*Note: The XRS-5 must be used with the TS-2 external temperature sensor when
operating with the OCM-3.
Velocity Input: » Belden 8760 or equivalent
7ML19985AB01 OCM III 11
Auxiliary Input: » Belden 8760 or equivalent
24 V Output: » Belden 8760
COMMUNICATION SOFTWARE
Milltronics Utilities Software on standard PC floppy disk for DOS 3.1 and up.
7ML19985AB01 OCM III 12
INSTALLATION
Installation shall only be performed by qualified personnel
and in accordance with local governing regulations.
INSTALLING THE OCM-3
The OCM-3 should be mounted in a clean, dry area that is: within the ambient
temperature range and suitable for the specified enclosure. The front cover should be
accessible for programming and viewing.
It is advisable to keep the OCM-3 away from high voltage or current runs, contactors
and SCR control drives.
Do not mount the OCM-3 in direct sunlight without the use of a sun shield.
This product is susceptible to electrostatic shock.
Follow proper grounding procedures.
209 mm
(8.2")
lid screws
(6 places)
106 mm
(4.2")
91 mm
(3.6")
16 mm
(0.6")
285 mm
(11.2")
267 mm
(10.5")
programmer
lid
suitable location for
conduit entrances
mounting holes
(accessed under
lid 4.3 mm (0.17")
dia.,4 places
enclosure
customer mounting
screw
Milltronics reccomends using a punch for making
holes in enclosure. Use suitable cable glands to
maintain ingress rating.
172 mm
(6.8")
OUTLINE AND MOUNTING
Non metallic enclosure does not provide grounding between connections.
Use grounding type bushings and jumpers.
13 OCM III 7ML19985AB01
OCM-3 LAYOUT
board A
board B
display
board
Hazardous voltage present on transducer terminals during operation.
dc terminals shall be supplied from SELV source in accordance
with IEC 1010-1 Annex H.
Relay contact terminals are for use with equipment having no accessible
live parts and wiring having insulation suitable for at least 250 V.
The maximum allowable working voltage between
adjacent relay contacts shall be 250 V.
All field wiring must have insulation suitable for at least 250 V.
14 OCM III 7ML19985AB01
SYSTEM DIAGRAM
98/03/05
OCM-3 Milltronics transducer,
see Specifications
Milltronics TS-2,
temperature sensor
customer device
customer alarm,
pump or control
device
customer device
customer device
customer device
Milltronics CVCC
mA output
relay output
auxiliary input
velocity input
RS-232
Maximum system capability. Not all components or their maximum quantity
may be required.
bi-polar current
(Milltronics communication)
15 OCM III 7ML19985AB01
INSTALLING THE TRANSDUCER
INSTALLING THE TEMPERATURE SENSOR
Max cable run 183 m (600 ft) of
RG-62U or equivalent. Cable must
be run in a grounded metal conduit
with no other cabling (except
Temp. Sensor cable).
Ground shield at OCM-3 only.
Insulate shield at junctions to
prevent inadvertent grounding.
Basic Wiring – Temperature Sensor
Basic Wiring – Transducer
Maximum cable run 183 m (600 ft) of
Beldon 8760, 1 pair shielded/twisted,
18 AWG or equivalent.
Temperature sensor cable can be
run with the transducer cable in a
grounded metal conduit.
Ground shield at OCM-3 only.
In order to compensate for uniform
temperature change in the air
between the transducer and the flow
surface, the temperature sensor
must be connected to the OCM-3.
Hazardous voltage present on transducer terminals during operation.
Note: When using the XRS-5 transducer with the OCM-3, use the TS-2 external
temperature sensor. The internal temperature sensor in the XRS-5 cannot be used.
16 OCM III 7ML19985AB01
mA OUTPUT
RELAYS
All relays are certified for use in equipment where the short circuit capacity of the
circuits in which they are connected is limited by fuses having ratings not exceeding
the rating of the relays.
isolated 0 or 4 to 20 mA output (P26) into 1 KΩ load maximum.
Wiring should conform to standard instrumentation practices.
Ground shield at OCM-3 only.
relays shown in de-energized state,
contacts rated at 5 A at 250 V
non-inductive.
n.c. com n.o. n.c. com n. o. n.c. com n. o.
17 OCM III 7ML19985AB01
SYNCHRONIZATION
Where two to a maximum of twelve transducers will be sharing a common conduit the
OCM-3s should be synchronized. In order to synchronize OCM-3s:
» remove jumper J1 on board A on all but one OCM-3
» interconnect the SYNC terminal (TB1-20) of all OCM-3s. Insure that
all OCM-3s share a common ground (TB1-34).
18 OCM III 7ML19985AB01
POWER CONNECTIONS
The OCM-3 power supply accepts 100, 115, 200 or 230 V ac per switch SW1
(board B) selection and 9 to 30 V dc.
The OCM-3 operates either under ac or dc power, or both ac and dc live
simultaneously. If both ac and dc power are live, the OCM-3 normally draws power
from the ac supply. In the event that the ac supply fails, the OCM-3 then draws power
from the dc supply.
The equipment must be protected by a 15 A fuse or
circuit breaker in the building installation.
A circuit breaker or switch in the building installation, marked
as the disconnect switch, shall be in close proximity to
the equipment and within easy reach of the operator.
9 to 30 Volt
dc input
negative dc input (TB1-24) is
tied to ground (TB1-34)
DC POWER
dc terminals shall be supplied from SELV source in accordance
with IEC 1010-1 Annex H.
100/115/200/230 V ac, 50/60 Hz,
select voltage via switch on board B
AC POWER
* switch shown in
‘OFF’ position,
select appropriate
voltage.
*
19 OCM III 7ML19985AB01
INSTALLING THE MEMORY BACK-UP BATTERY
The memory battery, B1 (see Specifications) should be replaced yearly to insure
memory back up during lengthy power outages. An on board capacitor provides
one hour of memory retention in order to preserve the memory while the battery
is being changed.
COMMUNICATING VIA COMPUTER
Refer to Communication.
INSTALLING THE PROGRAMMER
To program the OCM-3 via the Programmer, it must be placed into the front cover
recess of the OCM-3. The back of the Programmer has a magnetic plate which will
hold the programmer in place. It can be removed when programming is completed.
Do not install the memory back-up
battery until the OCM-3 is to be used.
The unit is supplied with one battery
package. Remove the battery from
the package and insert it into the
battery socket.
Refer to Operation \ Memory.
Disconnect power before installing or replacing the battery.
20 OCM III 7ML19985AB01
START UP
GENERAL
For the initial start up, it is advisable to use the programmer for programming the
OCM-3. The programmer transmits a coded infrared signal each time a key is pressed.
The OCM-3 is designed to automatically scroll through the ‘A’, ‘D’, ‘F’, ‘P’ and ‘U’
parameters in a structured sequence. The scrolling is interactive in that, depending on
the option chosen for a given parameter, subsequent parameters may be skipped or
modified. The user is thus prompted to satisfy only the parameters which are available
to him for the application he has chosen.
KEYPAD
access to ‘D’, ‘F’,
‘P’ and ‘U’
parameters
scrolls
Forward
through
the parameters / enters
content of entry field
scrolls
Backward
through the
parameters / clears content of entry field
negative
scrolls through selected
parameter options
access to ‘A’ parameters
/ initiates a printout while
viewing ‘Flow and Total’
numeric
entries with
decimal point
7ML19985AB01 OCM III 21
LEGEND
Press the associated programmer key:
Display shown on OCM-3:
Programmer key:
INITIAL START UP
After installation procedures have been completed, the OCM-3 may be powered up.
Upon initial powering up, the unit momentarily displays:
and then scrolls through the available languages:
The OCM-3 is asking which language you prefer to communicate in!
English language
selected
advance to ‘F0’
F0 enter security code
< - - -
(0) language
English
0
7ML19985AB01 OCM III 22
factory set security code
2.71828 must be entered
if the wrong language
was selected, it may
be changed here
continue programming by
entering the desired options
and advancing until the
scroll returns to ‘P0’. It is
then assumed that the
user has entered all the
required parameters.
For optimum calibration accuracy, an ‘F13’ should be performed prior to accessing
‘F2’, the normal operating mode.
enter the current head. The
OCM-3 calculates ‘P46’ and
automatically enters the value.
e.g. 1 6 0
P1 dimensional units
0centimeters
F13 auto zero calibration
P0 language
0 English
F13 auto zero calibration
0 completed
P0 language
0 English
3
1
8 2 8
72
1
F13 auto zero calibration
160
01 6
7ML19985AB01 OCM III 23
If data logging is desired, the time and date must be set.
e.g. 1141
11: 41 a.m.,
seconds are always
assumed to be 00
time is displayed in
hh:mm:ss
e.g. 12101492 October 12, 1492
The start up procedure is now complete. Enter ‘F2’ to place the OCM-3 in the normal
operating mode.
Note: To save parameter values, return to RUN mode (F2) after programming.
The OCM-3 now displays the flow rate and total. Refer to Operation \ Display
F4 24-hr. time
1141
4
11
F4 24-hr. time
11:41:00 enter new time
F5 (ddmmyyyy) date
F5 (ddmmyyyy) date
12/10/1492 enter new date
0 1
4
2
9 211 2
F4 24-hr. time
4
1
7ML19985AB01 OCM III 24
FUNDAMENTAL CHECKS
For accurate determination of flowrate, accurate head measurement is essential.
Check the following and correct if necessary.
» check D5 for correct temperature at transducer location.
» check D9 for correct distance from transducer to head.
» check D0 for accurate head measurement.
7ML19985AB01 OCM III 25
7ML19985AB01 OCM III 26
OPERATION
Upon power up, the transducer is fired periodically as set by P36. A long interval
between measurements may be desirable in order to conserve power* when
operating the OCM-3 from a DC source of limited capacity.
The echo is processed to determine the head (D0). The flow rate (D1) is calculated by
the OCM-3 as a mathematical function (P3 and P4) of head or a function of head and
velocity (P42). The flow rate is then integrated to yield the totalized flow (D2). The
‘Flow’ and ‘Total’ fields which are displayed during the normal running mode (F2) are
also continuously updated.
Viewing or changing the content of a parameter (except F1, emulation) is done
without disturbing the acquisition, processing or logging of flow data (see \ Security).
* restricted usage of display lighting (P14), relays (P15, 18 & 21), mA
output and communications will also conserve power.
MEMORY
During a power interruption, the memory back up will hold the programming, the log
and the totalizer values, and run the clock. The memory battery (B1) provides up to
one year of memory retention (see Appendices \ Maintenance).
Note: To save parameter values, return to RUN mode (F2) after programming.
SECURITY
The content of all ‘A’, ‘D’, ‘F’, ‘P’ and ‘U’ parameters can be viewed without having to
satisfy the security parameter, F0. However if it is desired to change the content of
any of these parameters, the security parameter must be satisfied (except for
resetting the running min/max displays, parameters D3/D4 and D6/D7).
Once security has been satisfied, access continues for 5 minutes after the last key is
pressed or until F2 is re-entered.
The security code may be changed from its factory set value, 2.71828, by entering a
new value into F10. It is imperative that the new value be recorded, as the code can
not be viewed. If the code is lost, consult Milltronics.
UNITS
Programming of the OCM-3 involves setting the units of measure:
» P1 linear and velocity
» P2 temperature
» P5 flow rate and volume
If the units are changed during the course of operation, the change will be effected
through all associated parameters and displays and will rescale flow and total data
stored in the logs.
7ML19985AB01 OCM III 27
FLOW CALCULATION
Absolute vs. ratiometric
The OCM-3 can be programmed to use either of two methods (P4) for calculating flow
from the head measurement: absolute or ratiometric. The result is the same
regardless of the method used. The principal difference is the information that must
be entered in order for the OCM-3 to carry out the calculation. The user’s choice of
method may ultimately be based upon the information which is at hand. Refer to U
parameters for the primary element selected for a listing of the information required.
For the ratiometric method, it is usually sufficient that the user know the flow rate
(Qcal) which occurs at maximum head (hcal).
On the other hand, absolute calculations require that the user enter information such
as: the physical dimensions of the primary element and the constant relating to units
of measure for both linear dimensions and flow rates.
e.g.
the general formula for flow through a single exponent primary element is:
Q = KHx
the specific formula for flow through a 45° V-notch weir is:
cfs = 1.03H2.5
thus: Q = flow in cubic feet per second
K = constant of 1.03
H = head in feet
The absolute method is not applicable to the following:
Palmer Bowlus flume
H flume
DISPLAY
The normal display during operation is the Flow and Total Display (F2).
status field
flow rate field
totalizer field
relay / "no echo" field
7ML19985AB01 OCM III 28
Flow Rate Field
Totalizer Field
Relay / No Echo Field
Status Field
The OCM-3 provides illumination for the LCD for easier viewing of the display.
Illumination can be set (P14) to be normally on or off, or automatic. When automatic is
selected, the lighting will automatically go on when keypad activity is sensed and then
extinguish after 15 seconds of inactivity.
DAMPING
The OCM-3 provides two separate damping functions: reading and mA output. Zero
or no damping allows fastest response while high or 100% provides the slowest
response. The damping is usually set to provide a reliable response without
sacrificing stability.
The reading damping, P13, dampens only the flow rate reading of the ‘Flow and Total’
display F2. The damping selections are: off, low, medium and high. Relay functions
associated with flow rate respond to the dampened reading values.
mA output damping, P27, dampens the change in the mA output. The parameter entry
is in seconds for spanning the 0 to 100% of the mA range selected (P26). Displays
and relay functions associated with the mA output respond to its
dampened value.
flow rate
total
units, P5
multiplier, P32
relay identification
under loss of echo
condition, "NO
ECHO" will
alternately flash
relay status : 0 = relay de-energized
1 = relay energized
* = alarm state (indicated when
flashing)
For battery operation, set display lighting to off or auto.
7ML19985AB01 OCM III 29
RELAYS
Three on board multipurpose relays are provided by the OCM-3. P15, 18 and 21 set
the respective functions for relays 1, 2 and 3. Depending on the function selected,
these parameters determine the need and configuration of the subsequent relay
control parameters, P16, 17 (relay 1); P19, 20 (relay 2) and P22, 23 (relay 3).
If the relay is to function as a driver for a remote totalizer or as a flow sampler contact,
the totalizer multiplier (P32) will be factored by the setpoint . Note that parameters
P16, P19, and P22 will default to zero. When a relay is set to totalizer (P32), you must
have the applicable parameter (P16 for relay 1, P19 for relay 2, or P22 for relay 3) set
to something other than zero (normally 1).
Example: For relay 1
Relay totalizer factor = totalizer factor (P32)
relay 1 setpoint (P16)
= 100 (P32=5)
2 (P16)
= 50 units/pulse
The status of each relay is shown in the display. Refer to \ Flow and Total Display.
mA OUTPUT
The OCM-3 provides a mA output (TB1-4/5) which can be assigned (P24) to
represent the measurement of flow, head, velocity or temperature. The associated
scaling, P25, is factory set to a value of ‘0’. This provides normal scaling with respect
to the assigned measurement.
Normal scaling for representation of flow, head or velocity is:
» 0 or 4 mA = 0
» 20 mA = maximum measurement value for: » P6*: flow rate
at maximum head
» P7: maximum head
» P10: velocity
at maximum head
Normal scaling for representation of temperature is:
» 0 or 4 mA = – 40 °C
» 20 mA = 60 °C
If custom scaling is required, the 20 mA corresponding value (other than 0) can be
entered into P25. The range (0 to 20 or 4 to 20 mA) and damping (see Damping) are
set via P26 and P27 respectively.
For battery operation, have relays energizing on alarm.
7ML19985AB01 OCM III 30
The mA function can be overridden for test purposes by setting the desired mA value
into F3. When the value is entered, the mA output will go to that value. When F3 is
exited, the mA output will revert to normal operation. Also, see \ Emulation Mode.
*In the case of absolute calculations (P4=0),
P6 is calculated by the OCM-3.
FAIL-SAFE
FLOW RATE AND TOTALIZING
Flow rate
Calculation of the flow rate is ongoing. It is normally viewed under the Flow and Total
display (F2) with the decimal point set per P33. It can also be viewed under D1 as the
raw flow calculation. Data on the running minimum and maximum flows that have
occurred since the last reset can be viewed in two ways:
» F7 gives the running min/max flows and their time and date of occurrence since
the last reset. F7 is reset by F8 but only after satisfying the security parameter F0.
» D3/D4 give the respective running min/max flow data, only, that have occurred
since they were last reset. D3/D4 are reset simultaneously by entering 0 into
either D3 or D4. D3 and D4 will then adopt the current flow rate and track the
running min/max values from that point on. The security parameter (F0) does
not need to be satisfied in order to reset D3/D4.
Flow data specific to a particular time and date can be viewed under the data log F14
(see \ Logging).
Totalizing
Totalizing of the calculated flow is ongoing. It is normally viewed under the Flow and
Total display (F2).
An auxiliary totalizer (D2) is provided for operator usage and is intended for short term
totalizing to a maximum count of 999999. It can be reset or preset independently of
the F2 totalizer after satisfying the security parameter (F0).
In order to adjust the rate of filling of the totalizer, the totalizer multiplier (P32) can be
set to an appropriate value. The totalizer can be reset via F11. Totalizing that is
specific to the time and date can be viewed under the data log F14.
The OCM-3 can be programmed to operate a remote totalizer by assigning any of the
relays (P15, 18 or 21) to act as a totalizer contact*. Under this function, the maximum
rate of contact closure is 2/sec with a closure duration of 200 msec**.
* The totalizer count is set by the relay setpoint parameter (P16, 19 or 22 respectively).
** Typically the totalizer should be set for 300 to 3000 counts per day at maximum flow.
In the event of an echo loss, the fail-safe timer will begin counting. If the echo loss
duration surpasses that of the time set (P29), a ‘
No Echo
’ alert will be displayed in the
Status field (see \ Display). The mA output will respond (P30) by either holding the last
value or immediately going to a predetermined value (P31). The head and derived flow
will hold their last value and totalization and logging will continue, based on that value.
Upon resumption of a valid echo, the mA output will return to a value corresponding to
the present value of the measurement assigned, at the mA damping rate (P27).
7ML19985AB01 OCM III 31
Under low flow conditions, a cut-off head (P45) can be entered to avoid totalizing
flows occurring at or below the flow corresponding to the cut-off head.
LOGGING
The OCM-3 provides an extensive logging feature which can be viewed on the local
display or retrieved via the serial communication link. The logging rate (P39) can be
fixed or variable. The latter being useful in conserving logging space. The condition for
variable logging is determined when selecting the logging rate.
Variable logging rate conditions are catagorized as : rate of change of flow, percent of
maximum flow or percent of maximum head. Logging occurs at the normal (slower)
rate while the condition is less than the setpoint (P40). If the condition exceeds the log
rapid setpoint, the rapid rate of logging takes effect until the condition falls below the
log normal setpoint (P41).
The associated setpoint units are : % change of maximum flowrate per minute, % of
maximum flowrate and % of maximum head, respectively. The setpoints represent the
absolute value of the rate of change; that is, for either increasing or decreasing
flowrate. The OCM-3 does not recognize negative entries into P-40 and P-41.
Flow data is logged in 1/2 % increments from 0 to 110 % of maximum flow. Flows
above 110 % are logged as 110 %. Truncation of flows to 110 % does not apply to
daily totalization.
Log Capacity vs Rates
rate capacity
1 min 31 days
5 3 months
15 9 months
30 1 year
60 1.5 years
24 hr 2 years
e.g. 15 / 5 9 months max / 3 months min
Once the log is filled, the old data will be successively written over with the new
data being logged.
The log can be examined via F14. Viewing of the log is done by task and by method.
The viewing tasks are: daily flow totals, flow rates and min-max flow data for flow or
temperature. The viewing methods are: by first entry, by last entry and by specified
date. The scrolling keys are used to maneuver through the tasks, methods and
time of day.
7ML19985AB01 OCM III 32
Viewing the data log
The day totalizer (F14) does not use the master totalizer multiplier (P32). It is possible
that the daily total overflows. In such a case the display will show +++.++.
7ML19985AB01 OCM III 33
BLANKING
Blanking is used to ignore the zone in front of the transducer where ringing or other
false echo is at a level that interferes with the processing of the true echo. The
minimum blanking is factory set, but can be overridden by entering the desired
distance into P47.
Ringing is the inherent nature of the transducer mass to continue vibrating after the
transducer has been fired. Ringing decays to acceptable levels in the order of
milliseconds. Excessive cold or over tightening of the transducer mounting may
increase the ring time such that it appears as an echo during the receive cycle. This is
usually indicated by an incorrect high head reading. Excessive ring time may be
overcome by increasing the blanking.
TEMPERATURE
The temperature as currently registered by the temperature sensor is viewed under
D5. Data on the running minimum and maximum temperatures that have occurred
since the last reset can be viewed in several ways:
F7 gives the running min/max temperatures and their time and date of occurrence
since the last reset. F7 is reset by F8 but only after satisfying the security
parameter F0.
D6/D7 give the respective running min/max temperature data, only, that have
occurred since they were last reset. D6 is reset by entering a value lower than D5,
and D7 is reset by entering a value larger than D5. D6 and D7 will then adopt the
current temperature value and track the min/max values from that point on. The
security parameter F0 does not need to be satisfied in order to reset D6 or D7.
Temperature data specific to the time and date can be viewed under the data log F14
(see \ Logging).
D14 indicates the resistance of the temperature sensor corresponding to the
temperature shown in D5.
TIME AND DATE
If the data logging features of the OCM-3 are to be used, the time (F4) and date (F5)
must be set. The day starts at 00:00:00 and ends at 23:59:59.
Adjusting the Time
If the clock time is advanced beyond the next anticipated logging time, the entry for
each missed logging time is filled with a code which indicates that the system was not
able to make entries at those times.
The daily total will be reduced proportional to the amount of time the day
was shortened.
If the clock time is set back beyond the preceding logging time, the previously logged
date will be written over with new data as the logging proceeds.
7ML19985AB01 OCM III 34
The daily total will be increased proportional to the amount of time the day was
lengthened.
Adjusting the Date
If the calendar is reset, the OCM-3 will adjust the log dates accordingly, taking into
account leap years and days per month.
EMULATION MODE
The flow calculation (P3/P4) can be checked for accuracy by using the emulation
parameter F1. The head is entered and the corresponding flow is displayed. This
function is useful when troubleshooting discrepancies between the OCM-3 calculation
and the expected flow.
Relays assigned to functions associated with the emulation parameter respond to the
emulated flows.
The mA output does not track the emulated flows when P28 (mA output emulation) =
0. However, if it is required to do so, then the emulator parameter should be set to 1.
RESET
The following resets can only be executed after satisfying the security access, F0.
Cold Start
If it is desired to reset all parameters, logs and totalizers to their factory setting, this is
done by forcing a cold start, F12.
Master Totalizer
If it is desired to reset the master totalizer (F2), this is done by parameter F11.
Data Log
If it is desired to reset the data log (F14), this is done by parameter F15.
Min/Max Log
If it is desired to reset the min/max log (F7), this is done by parameter F8.
7ML19985AB01 OCM III 35
FLOW VELOCITY INPUT
In some applications, the flow calculation for the chosen primary element requires a
velocity input. In this type of application, the transducer measurement is used to
calculate the cross sectional area of the flow. By multiplying the area with the distance
per time units of velocity, the volume per time units of flow are calculated. The
calculated velocity can be viewed via D8.
The 0% and 100% limits of the velocity input must be scaled using parameters
P8 and P9.
» select P8
» enter the voltage corresponding to zero velocity
» select P9
» enter the velocity corresponding to 5 V
e.g. If the velocity sensor output is 1 V per m/sec and the output is
scaled for 7 V at 100% velocity (7 m/sec), then enter 5 m/sec. If the
output is scaled for 4 V at 100% velocity (4 m/sec), enter 5 m/sec.
P8 and P9 can only be accessed if P3 has been set for an option that requires the use
of a velocity input. The input voltage level can be viewed via D12.
AUXILIARY HEAD INPUT
In some applications, the transducer input (TB1-1/2) is not used to provide a signal for
head measurement. A typical example of this is an application which is beyond the 3
m (10 ft) range of the OCM-3. In such a case, the head could be derived from another
Milltronics level monitor or other compatible device.
The method of head determination is set by P42. The OCM-3 simply substitutes the
signal from the auxiliary device for the ultrasonic measurement provided by the
transducer. The programming and consequent flow calculation are performed
as normal.
typical 1 - 5 V signal from
velocity sensor.
typical 4 - 20 mA signal from velocity sensor.
Add terminating resistor.
e.g. 250 Ω for 1 - 5 V over 4 - 20 mA.
Current Input
Velocity Input (additional to Basic Wiring)
Signal must be positive with respect to ground.
Voltage Input
7ML19985AB01 OCM III 36
The 0% and 100% limits of the auxiliary input must be scaled using parameters P43
and P44.
» select P43
» enter the voltage corresponding to zero head
» select P44
» enter the head corresponding to 5 V.
e.g. if the head output is 1 V per m and the output is scaled for 7 V at
100% head (7 m), then enter 5 m. If the output is scaled for 4 V at
100% head (4 m), enter 5 m.
P43 and P44 can only be accessed if P42 has been set for head determination by an
auxiliary device. The input voltage level can be viewed via D13.
DC OUTPUT
The OCM-3 provides a 24 V DC output that can be used to supply power to a remote
customer device. The output is not isolated from the DC rails that supply the OCM-3
electronics and no overload protection is provided. As such, the output must not
operate beyond its specified capacity.
DIAGNOSTIC AIDS
D15 through D18 are diagnostic aids to Milltronics service personnel when
troubleshooting system problems.
D18 also serves as a performance indicator by displaying the number of valid echos
received as a percentage of the number of pulses being fired by the transducer. A low
value indicates that a large proportion of the pulses fired are not producing valid
echos. In such instances, the transducer should be checked for proper mounting and
aiming or the transducer wiring checked for excessive noise. If the value is zero,
shorted or opened transducer wiring may be suspect.
Current Input
Auxiliary Input (additional to Basic Wiring)
Voltage Input
typical 1 - 5 V signal from
auxiliary device.
typical 4 - 20 mA signal from auxiliary device.
Add terminating resistor.
e.g. 250 Ω for 1 - 5 V over 4 - 20 mA.
Signal must be positive with respect to ground.
7ML19985AB01 OCM III 37
‘D’ PARAMETER LISTING
Refer to ‘Operation’ for details.
D0 head
D1 flow rate
D2 short total *
D3 maximum flow rate
D4 minimum flow rate
D5 temperature
D6 maximum temperature
D7 minimum temperature
D8 velocity ✧
D9 nominal target range
D10 analog milliamps
D11 internal DC volts
D12 velocity volts ✧
D13 auxiliary input volts
D14 temperature sensor ohms
D15 self-test checksum
D16 restarts
D17 exceptions
D18 valid echos per 100
*
security access required
✧ applicable to flow calculations requiring velocity sensor
7ML19985AB01 OCM III 39
7ML19985AB01 OCM III 40
‘F’ PARAMETER LISTING
Refer to ‘Operation’ for details.
F0 enter security code
F1 emulation mode*
F2 run mode
F3 keypad to mA output *
F4 show time
set time*
F5 show date
set date*
F6 software identification number
F7 view min/max data
F8 reset min/max data*
F9 self check*
F10 change security code*
F11 reset master totalizer*
F12 force a cold start*
F13 auto zero calibration*
F14 examine data log:
task: view daily totals
view flow rates
view min/max data
method:
first day
last day
specified day
F15 clear data log*
*
security access required
7ML19985AB01 OCM III 41
7ML19985AB01 OCM III 42
‘P’ PARAMETER LISTING
Refer to ‘Operation’ for details.
P0 language
0 = english
1 = french
2 = italian
3 = german
4 = spanish
P1 dimensional units
linear velocity
0 = centimetres centimetres per second
1 = inches inches per second
2 = feet feet per second
3 = metres metres per second
P2 temperature units
0 = Celcius
1 = Fahrenheit
P3 primary element
0 = exponential device
1 = BS-3680 Rectangular Flume
2 = BS-3680 Round Nose Horizontal Crest Weir
3 = BS-3680 Trapezoidal Flume
4 = BS-3680 U-throated Flume
5 = BS-3680 Finite Crest Weir
6 = BS-3680 Thin Plate Rectangular Weir
7 = BS-3680 Thin Plate V-notch Weir
8 = Rectangular Weir (contracted)
9 = Round Pipe
10 = Palmer Bowlus Flume
11 = H Flume
12 = Universal Head vs. Flow
7ML19985AB01 OCM III 43
13 = Rectangular Area x Velocity
14 = Trapezoidal Area x Velocity
15 = Modified Trapezoidal Area x Velocity
16 = U-channel Area x Velocity
17 = Circular Area x Velocity
18 = Gull-wing Area x Velocity
19 = Egg-shaped Area x Velocity
20 = Universal Area x Velocity
P4 method of calculation
0 = absolute
1 = ratiometric
P5 flow rate units
flowrate
volume
0 = litres per second litres
1 = cubic feet per second cubic feet
2 = imperial gallons per minute imperial gallons
3 = U.S. gallons per minute U.S. gallons
4 = imperial million gallons per day imperial million gallons
5 = U.S. million gallons per day U.S. million gallons
6 = cubic metres per hour cubic metres
7 = cubic metres per day cubic metres
P6 flow at maximum head
P7 height of maximum head
P8 volts in at zero velocity
P9 velocity at 5 volts in
P10 velocity at maximum flow
7ML19985AB01 OCM III 44
P13 display damping
0 = off
1 = low
2 = med
3 = high
P14 display lighting
0 = on
1 = auto off
2 = off
P15 / P18 / P21 relay 1 / 2 / 3 assignment
0 = not in service
1 = de-energize on loss of echo
2 = energize on loss of echo
3 = de-energize on high flow rate
4 = energize on high flow rate
5 = de-energize on low flow rate
6 = energize on low flow rate
7 = de-energize on high head
8 = energize on high head
9 = de-energize on low head
10 = energize on low head
11 = de-energize on high velocity
12 = energize on high velocity
13 = de-energize on low velocity
14 = energize on low velocity
15 = de-energize on high analog
16 = energize on high analog
17 = de-energize on low analog
18 = energize on low analog
19 = de-energize on low D11 volts
20 = energize on low D11 volts
21 = de-energize on high D11 volts
22 = energize on high D11 volts
23 = de-energize on low Aux. volts
7ML19985AB01 OCM III 45
24 = energize on low Aux. volts
25 = de-energize on high Aux. volts
26 = energize on high Aux. volts
27 = de-energize up control on head
28 = energize up control on head
29 = de-energize down control on head
30 = energize down control on head
31 = de-energize up control on analog
32 = energize up control on analog
33 = de-energize down control on analog
34 = energize down control on analog
35 = ( pulse ) flow totalizer
36 = ( pulse ) sampler by volume
37 = ( pulse ) sampler by time
38 = ( pulse ) by time of day
P16 / P19 / P22 relay 1 / 2 / 3 high setpoint
P17 / P20 / P23 relay 1 / 2 / 3 low setpoint
P24 mA assignment
0 = flow rate
1 = head
2 = velocity
3 = temperature
P25 If custom mA, 20 mA = ?
0 = normal
0 = custom
P26 mA span
0 = 4-20 mA
1 = 0-20 mA
7ML19985AB01 OCM III 46
P27 mA damping (secs)
P28 mA options (emulator tracking)
0 = don’t track emulator
1 = track emulator
P29 fail-safe time (secs)
P30 fail-safe analog mode
0 = hold last value
1 = assume value in P31
P31 fail-safe analog mA (default value)
P32 totalizer multiplier
0 = x 1/1000 (0.001)
1 = x 1/100 (0.01)
2 = x 1/ 10 (0.1)
3 = x 1
4 = x 10
5 = x 100
6 = x 1000
P33 flow rate display (decimal point)
0 = no decimal places
1 = 1
2 = 2
3 = 3
4 = 4
7ML19985AB01 OCM III 47
P34 printer mode
0 = never print
1 = interval to be in minutes
2 = interval to be in hours
3 = print once each day
P35 printer timing
P36 measurement interval
0 = 1 sec
1 = 15 sec
2 = 30 sec
3 = 1 min
4 = 5 min
P37 serial data rate
0 = 300 baud
1 = 600
2 = 1200
3 = 2400
4 = 4800
5 = 9600
6 = 19200
P38 site number
7ML19985AB01 OCM III 48
P39 data logging rate
fixed
0 = 1 min 3 = 30
1 = 5 4 = 60
2 = 15 5 = 24 hr
variable
(condition)
6 = 15/1 min (% flow / min) 19 = 60 / 1 (flow)
7 = 15 / 5 " 20 = 60 / 5 "
8 = 30 / 1 " 21 = 24 hr / 1 min "
9 = 30 / 5 " 22 = 24 hr / 5 min "
10 = 60 / 1 " 23 = 24 hr / 15 min "
11 = 60 / 5 " 24 = 15 / 1 min (head)
12 = 24 hr / 1 min " 25 = 15 / 5 "
13 = 24 hr / 5 min " 26 = 30 / 1 "
14 = 24 hr / 15 min " 27 = 30 / 5 "
15 = 15 / 1 min (flow) 28 = 60 / 1 "
16 = 15 / 5 " 29 = 60 / 5 "
17 = 30 / 1 " 30 = 24 hr / 1 min "
18 = 30 / 5 " 31 = 24 hr / 5 min "
32 = 24 hr / 15 min "
P40 log rapid setpoint
P39 variable logging condition units
% flow / min % change of maximum flow per minute
flow % of maximum flow
head % of maximum head
P41 log normal setpoint
P39 variable logging condition units
% flow / min % change of maximum flow per minute
flow % of maximum flow
head % of maximum head
7ML19985AB01 OCM III 49
P42 head determination
0 = by OCM-3
1 = by auxiliary device
P43 volts in for zero head
P44 head at 5 volts in
P45 low flow cut-off head
P46 range at zero head
P47 blanking distance
7ML19985AB01 OCM III 50
‘U’ PARAMETERS FOR P3 PRIMARY ELEMENT
The number of ‘U’ parameters required varies according to the primary element
chosen (P3) and the method of calculation (P4). The OCM-3 prompts the user by
displaying the next required parameter, insuring the programming is complete.
The following is a list of the specific primary elements to which the OCM-3 can
be applied.
Refer to the page covering your particular application; the rest may be disregarded.
P3 primary element
0 exponential device (e.g. proportional, V-notch, Parshall etc)
1 BS-3680 Rectangular Flume (ISO 4359)
2 BS-3680 Round Nose Horizontal Crest Weir (ISO 4374)
3 BS-3680 Trapezoidal Flume (ISO 4359)
4 BS-3680 U-throated Flume (ISO 4359)
5 BS-3680 Finite Crest Weir (ISO 3846)
6 BS-3680 Thin Plate Rectangular Weir (ISO 1438/1)
7 BS-3680 Thin Plate V Notch Weir (ISO 1438/1)
8 Rectangular Weir (contracted)
9 Round Pipe
10 Palmer-Bowlus Flume
11 H Flume
12 Universal Head vs. Flow
13 Rectangular Area x Velocity
14 Trapezoidal Area x Velocity
15 Modified Trapezoidal Area x Velocity
16 U-channel Area x Velocity
7ML19985AB01 OCM III 51
17 Circular Area x Velocity
18 Gull Wing Area x Velocity
19 Egg-shaped Area x Velocity
20 Universal Area x Velocity
The primary element must be installed in accordance with the manufacturers
recommendations and in accordance with all governing regulations.
7ML19985AB01 OCM III 52
SIMPLE EXPONENTIAL DEVICES, P3 = 0
‘U’ parameters required *
U0 = exponent
U1 = k factor (P4 = 0 only)
Typical Exponential Devices:
» Sutro (proportional) weir
» head measurement only
» Rectangular (suppressed) or Trapezoidal (Cipolletti) weir
» Kahfagi venturi
» Parshall flume
» Leopold Lagco
» Triangular (V-notch) weir
*obtain from manufacturer’s specifications.
Reference
ABSOLUTE CALCULATION, P4 = 0¤
For flows that can be calculated by the equation:
q = k hx
where q = flowrate x = exponent (U0)
k = constant factor (U1) h = head
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal (h/hcal)x
where q = flowrate qcal = flowrate at maximum head
h = head hcal = maximum head
x = exponent (U0)
Refer to manufacturers specifications for the exponent value.
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 53
SIMPLE EXPONENTIAL DEVICES, P3 = 0
TYPICAL SHARP-CRESTED WEIRS
Typical Weir Profiles
For rated flows under free flow conditions, the head is measured upstream of the weir
plate at a minimum distance of 3 times the maximum head (i.e. where the liquid
surface is not affected by drawdown).
transducer *
Rectangular - suppressed
U 0 = 1.5
V - notch or Triangular
U 0 = 2.5
Sutro (Proportional)
U 0 = 1
(symmetrical or asymmetrical)
Trapezoidal (Cipolletti)
U 0 = 1.5
* The transducer must be above the maximum head by at least the
blanking value, P47.
minimum
3 x h max
7ML19985AB01 OCM III 54
SIMPLE EXPONENTIAL DEVICES, P3 = 0
KHAFAGI VENTURI
For rated flows under free flow conditions, the head is measured 15 cm (6") upstream
from the beginning of the converging section.
* The transducer must be above the maximum head by at least the
blanking value, P47.
15 cm (6")
plan
0
head
front side
transducer *
7ML19985AB01 OCM III 55
SIMPLE EXPONENTIAL DEVICES, P3 = 0
TYPICAL PARSHALL FLUME
For rated flows under free flow conditions, the head is measured at 2/3 the length of
the converging section upstream of the beginning of the throat section.
* The transducer must be above the maximum head by at least the
blanking value, P47.
2/3 C
C
plan
side
front
0
head
transducer *
7ML19985AB01 OCM III 56
SIMPLE EXPONENTIAL DEVICES, P3 = 0
TYPICAL LEOPOLD LAGCO
For rated flows under free flow conditions, the head is measured at a point upstream
referenced to the beginning of the converging section. Refer to the following table.
converging
side front
0
head
transducer *
diverging
plan
Q
throat
point of measurement
Flume Size Point of Measurement
(pipe dia. in inches) mm inches
4 - 12 25 1.0
15 32 1.3
18 38 1.5
21 44 1.8
24 51 2.1
30 64 2.5
36 76 3.0
42 89 3.5
48 102 4.0
54 114 4.5
60 127 5.0
66 140 5.5
72 152 6.0
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 57
BS-3680 Rectangular Flume, P3 = 1
‘U’ parameters required * ‘U’ parameters calculated **
U0 = approach width B U4 = Cv
U1 = throat width b U5 = Cd
U2 = hump height p U6 = A
U3 = throat length L
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
Reference
ABSOLUTE CALCULATION, P4 = 0¤
For flows that can be calculated by the equation:
q = (2/3)1.5 x g0.5 x Cv x Cs x Cd x B x h1.5
where : q = flow rate Cv = velocity coefficient
b = throat width Cs = shape coefficient
g = gravitational acceleration Cd = discharge coefficient
h = head
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x Cd/Cdcal x Cv/Cvcal x (h/hcal)1.5
where : q = flow rate
qcal = flow rate at maximum head
h = head
hcal = maximum head
Cv = velocity coefficient
Cvcal = velocity coefficient for maximum head
Cd = discharge coefficient for head
Cdcal = discharge coefficient for maximum head
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 58
BS-3680 RECTANGULAR FLUME
3 to 4 x hmax L
transducer *
h
0
head
p
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 59
BS-3680 Round Nose Horizontal Crest Weir, P3 = 2
‘U’ parameters required * ‘U’ parameters calculated **
U0 = crest width b U3 = Cv
U1 = crest height p U4 = Cd
U2 = crest length L U5 = A
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
Reference
ABSOLUTE CALCULATION, P4 = 0¤
For flows that can be calculated by the equation:
q = (2/3)1.5 x g0.5 x Cv x Cs x Cd x b x h1.5
where : q = flow rate Cv = velocity coefficient
g = gravitational acceleration Cs = shape coefficient
b = throat width Cd = discharge coefficient
h = head
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x Cd/Cdcal x Cv/Cvcal x (h/hcal)1.5
where : q = flow rate
qcal = flow rate at maximum head
h = head
hcal = maximum head
Cv = velocity coefficient
Cvcal = velocity coefficient for maximum head
Cd = discharge coefficient for head
Cdcal = discharge coefficient for maximum head
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 60
BS-3680 ROUND NOSE HORIZONTAL CREST WEIR
transducer *
3 to 4 x hmax
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 61
BS-3680 TRAPEZOIDAL FLUME, P3 = 3
‘U’ parameters required * ‘U’ parameters calculated **
U0 = approach width B U5 = Cv
U1 = throat width b U6 = Cd
U2 = hump height p U7 = Cs
U3 = throat length L U8 = A
U4 = slope m
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
Reference
ABSOLUTE CALCULATION, P4 = 0¤
For flows that can be calculated by the equation:
q = (2/3)1.5 x g0.5 x Cv x Cs x Cd x b x h1.5
where : q = flow rate Cv = velocity coefficient
g = gravitational acceleration Cs = shape coefficient
b = throat width Cd = discharge coefficient
h = head
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x Cs/Cscal x Cd/Cdal x Cv/Cvcal x (h/hcal)1.5
where :
q = flow rate Cscal = shape coefficient for maximum head
qcal = flow rate at maximum head Cv = velocity coefficient
h = head Cvcal = velocity coefficient for maximum head
hcal = maximum head Cd = discharge coefficient for head
Cs = shape coefficient for head Cdcal = discharge coefficient for maximum head
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 62
BS-3680 TRAPEZOIDAL FLUME
p
side
transducer *
plan
L
end
p
h
B
3 to 4 x hmax
b
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 63
BS-3680 U-Flume, P3 = 4
‘U’ parameters required * ‘U’ parameters calculated **
U0 = approach diameter Da U4 = Cv
U1 = throat diameter D U5 = Cd
U2 = hump height p U6 = Cu
U3 = throat length L U7 = A
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
Reference
ABSOLUTE CALCULATION, P4 = 0¤
For flows that can be calculated by the equation:
q = (2/3)1.5 x g0.5 x Cv x Cu x Cd x D x h1.5
where : q = flow rate Cv = velocity coefficient
g = gravitational acceleration Cu = shape coefficient
b = throat width Cd = discharge coefficient
h = head
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x Cu/Cucal x Cd/Cdcal x Cv/Cvcal x (h/hcal)1.5
where : q = flow rate
qcal = flow rate at maximum head
h = head
hcal = maximum head
Cu = shape coefficient for head
Cucal = shape coefficient for maximum head
Cv = velocity coefficient
Cvcal = velocity coefficient for maximum head
Cd = discharge coefficient for head
Cdcal = discharge coefficient for maximum head
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 64
BS-3680 U-FLUME
L
p
h
D
3 to 4 x hmax
Da
transducer *
0
head
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 65
BS-3680 FINITE CREST WEIR, P3 = 5
‘U’ parameters required * ‘U’ parameters calculated **
U0 = crest width b U3 = C
U1 = crest height p U4 = Cp
U2 = crest length L
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
Reference
ABSOLUTE CALCULATION, P4 = 0¤
For flows that can be calculated by the equation:
q = (2/3)1.5 x g0.5 x C x Cp x b x h1.5
where : q = flow rate C = a function of h and L
g = gravitational acceleration
b = crest width Cp = a correction factor as a function
h = head of h and p applied to C
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x C/Ccal x Cp/Cpcal x (h/hcal)1.5
where : q = flow rate
qcal = flow rate at maximum head
h = head
hcal = maximum head
C = discharge coefficient for head
Ccal = discharge coefficient for maximum head
Cp = correction factor for C
Cpcal = correction factor for Ccal
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 66
BS-3680 FINITE CREST WEIR
transducer *
3 to 4 x hmax
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 67
BS-3680 THIN PLATE RECTANGULAR WEIR, P3 = 6
‘U’ parameters required * ‘U’ parameters calculated **
U0 = approach width B U3 = Ce
U1 = crest width b U4 = Kb
U2 = crest height p
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
Reference
ABSOLUTE CALCULATION, P4 = 0¤
For flows that can be calculated by the equation:
q
=
Ce
x
2⁄3 √⎯⎯⎯2
g
x
be
x
(
h
e
)1.5
where : q = flow rate Ce = a function of h, p, b and B
g = gravitational acceleration be = effective crest width (b + Kb)
b = crest width he = effective head (h + Kh)
h = head Kh = 1 mm
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x Ce/Cecal x (h/hcal)1.5
where : q = flow rate
qcal = flow rate at maximum head
h = head
hcal = maximum head
Ce = discharge coefficient for head
Cvcal = discharge coefficient for maximum head
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 68
BS-3680 THIN PLATE RECTANGULAR WEIR
4 to 5 x hmax
transducer *
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 69
BS-3680 THIN PLATE V-NOTCH WEIR, P3 = 7
‘U’ parameters required * ‘U’ parameters calculated **
U0 = notch angle alpha U1 = Ce
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
Reference
ABSOLUTE CALCULATION, P4 = 0¤
For flows that can be calculated by the equation:
q = Ce x 8/15 x tan(α/2) x (2g)0.5 x h2.5
where : q = flow rate h = head
g = gravitational acceleration Ce = function of h and α
α = notch angle alpha◊
◊ angle is restricted to 90°, 53.133° or 28.066°. Otherwise use ratiometric calculation.
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x Ce/Cecal x (h/hcal)2.5
where : q = flow rate
qcal = flow rate at maximum head
h = head
hcal = maximum head
Ce = discharge coefficient for head
Cecal = discharge coefficient for maximum head
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 70
BS-3680 THIN PLATE V-NOTCH WEIR
transducer *
4 to 5 x hmax
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 71
RECTANGULAR WEIR (CONTRACTED), P3 = 8
‘U’ parameters required *
U0 = crest width b
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
Reference
ABSOLUTE CALCULATION, P4 = 0¤
For flows that can be calculated by the equation:
q = K x (b - 0.2h) x h1.5
where : q = flow rate
h = head
K = constant
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x (b - 0.2h)/(b - 0.2hcal) x (h/hcal)2.5
where : q = flow rate
qcal = flow rate at maximum head
h = head
hcal = maximum head
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 72
RECTANGULAR WEIR - CONTRACTED
transducer *
4 to 5 x hmax
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 73
ROUND PIPE, P3 = 9
(based on the Manning Formula)
‘U’ parameters required *
U0 = pipe inside diameter D
U1 = slope (fall/run) s
U2 = roughness coefficientn
*obtain from manufacturer’s specifications.
Reference
ABSOLUTE CALCULATION, P4 = 0¤
For flows that can be calculated by the equation:
q = K/n x f(h) x s0.5
where : q = flow rate
h = head
K = constant
f(h) = A x R0.66
A = cross sectional area
R = hydraulic radius
s = slope of hydraulic gradient
n = roughness coefficient
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x f(h)/f(hcal)
where : q = flow rate h = head
qcal = flow rate at maximum head hcal = maximum head
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 74
ROUND PIPE
h
transducer
*
**
* This dimension should be at least 15 cm (6") shorter than
the blanking value, P47.
** The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 75
PALMER-BOWLUS FLUME *, P3 = 10
‘U’ parameters required **
U0 = maximum flume width, hmax
*typically those manufactured by Warminster or Plasti-Fab.
**obtain from manufacturer’s specifications.
Reference
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x f(h/hmax) / f(hcal/hmax)
where : q = flow rate
qcal = flow rate at maximum head
h = head
hcal = maximum head
f(h/hmax) is determined by polynomial synthesis
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 76
PALMER-BOWLUS FLUME
D = pipe or sewer diameter
0
head
D / 2, point of measurement * transducer **
* for rated flows under free flow conditions
** The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 77
H-FLUME *, P3 = 11
‘U’ parameters required *
U0 = maximum listed head, hmax
*as developed by the U.S. Department of Agriculture, Soil Conservation Service.
**obtain from manufacturer’s specifications.
Reference
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x f(h/hmax)/f(hcal/hmax)
where : q = flow rate
qcal = flow rate at maximum head
f(h/hmax) and f(hcal/hmax) are determined by polynomial synthesis
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 78
H-FLUME
front
point of measurement
side
transducer *
plan
Flume Size Point of Measurement
D (feet) cm inches
0.5 4.7 1.88
0.75 6.7 2.69
1.0 9.1 3.63
1.5 13.5 5.38
2.0 17.9 7.19
2.5 22.5 9.00
3.0 27.2 10.88
4.5 40.5 16.19
For rated flows under free flow conditions, the head is measured at a point downstream
from the flume entrance. Refer to the following table.
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 79
UNIVERSAL HEAD vs FLOW, P3 = 12
The flow curve is characterized by entering the head (Aeven) and flow (Aodd)
ordinates for the number of data points (n, 4 to 16) over the flow range. The first
point (A0,A1) generally being at 0 head and the last point (A2n-2,A2n-1) generally being
at maximum head .
‘U’ parameters required *
U0 = number of data points (n, 4 to 16)
Aeven = head
Aodd = flow rate
*obtain from manufacturer’s specifications.
Reference
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x f(h)/f(hcal)
where : f(h) and f(hcal) are polynomials based on interpolation of data points
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 80
UNIVERSAL HEAD vs FLOW
e.g. typical compound weir
Parameters
U0 = 11
A0 = 0 head, point 1 A12 = 1.05 head, point 7
A1 = 0 flow, point 1 A13 = 2.65 flow, point 7
A2 = 0.3 head, point 2 A14 = 1.2 head, point 8
A3 = 0.1 flow, point 2 A15 = 3.4 flow, point 8
A4 = 0.6 head, point 3 A16 = 1.4 head, point 9
A5 = 0.7 flow, point 3 A17 = 5.0 flow, point 9
A6 = 0.8 head, point 4 A18 = 1.7 head, point 10
A7 = 1.5 flow, point 4 A19 = 8.0 flow, point 10
A8 = 0.95 head, point 5 A20 = 2 head, point 11
A9 = 2.25 flow, point 5 A21 = 11.8 flow, point 11
A10 = 1 head, point 6
A11 = 2.5 flow, point 6
Head A even
A odd
F
l
o
w
R
a
t
e
For best accuracy concentrate data points where changes in flow rate are the greatest.
7ML19985AB01 OCM III 81
RECTANGULAR AREA X VELOCITY, P3 = 13
‘U’ parameters required * ‘U’ parameters calculated **
U0 = channel width B U1 = area (h)
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
Reference
ABSOLUTE CALCULATION, P4 = 0¤
For flows that can be calculated by the equation:
q = 1/1000 x B x h x V
where : q = flow rate in l/sec
B = channel width in cm
h = head in cm
V = velocity in cm/sec
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x A/Acal x v/vcal
where : q = flow rate
qcal = flow rate at maximum head
h = head
hcal = maximum head
v = velocity
vcal = velocity at maximum head
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 82
RECTANGULAR AREA X VELOCITY
transducer *
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 83
TRAPEZOIDAL AREA X VELOCITY, P3 = 14
‘U’ parameters required * ‘U’ parameters calculated **
U0 = channel top width B U3 = area (h)
U1 = channel base width b
U2 = channel depth ht
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
Reference
ABSOLUTE CALCULATION, P4 = 0¤
For flows that can be calculated by the equation:
q = 1/1000 x (b + mh) x v
m = (B - b)/d
where : q = flow rate, l/sec
B = channel top width, cm
b = channel bottom width, cm
d = depth of channel, cm
h = head, cm
v = flow velocity, cm/sec
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x A/Acal x v/vcal
A = (b + mh) x h
Acal = (b + mhcal) x hcal
m = (B - b)/d
where : q = flow rate, l/sec
B = channel top width, cm
b = channel bottom width, cm
d = depth of channel, cm
h = head, cm
v = flow velocity, cm/sec
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 84
TRAPEZOIDAL AREA X VELOCITY
transducer *
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 85
MODIFIED TRAPEZOIDAL AREA X VELOCITY, P3 = 15
‘U’ parameters listed * ‘U’ parameters calculated **
U0 = channel top width B U3 = area (h)
U1 = channel base width b
U2 = transition height ht
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
Reference
ABSOLUTE CALCULATION, P4 = 0¤
For flows that can be calculated by the equation:
q = 1/1000 x (b + mh) x v for h ≤ d
q = 1/1000 x ((b + md)d + (B(h - d))) x v for h ≥ d
m = (B - b)/d
where : q = flow rate, l/s d = height of transition, cm
B = channel top width, cm h = head, cm
b = channel base width, cm v = flow velocity, cm/sec
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x A/Acal x v/vcal
for h ≤ d: A = (b + mh) x h
Acal = (b + mhcal) x hcal
for h ≥ d: A = (b + md) x d + B(h - d)
Acal = (b + md) x d + B(hcal - d)
m = (B - b)/d
where : q = flow rate d = depth of channel
qcal = flow rate at hcal h = head
B = channel top width, cm v = flow velocity, cm/sec
b = channel base width, cm
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 86
MODIFIED TRAPEZOIDAL AREA X VELOCITY
transducer *
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 87
U-CHANNEL AREA X VELOCITY, P3 = 16
‘U’ parameters required * ‘U’ parameters calculated **
U0 = base diameter D U1 = area (h)
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
7ML19985AB01 OCM III 88
U-CHANNEL AREA x VELOCITY
transducer *
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 89
CIRCULAR AREA X VELOCITY, P3 = 17
‘U’ parameters listed * ‘U’ parameters calculated **
U0 = conduit diameter ID U1 = area (h)
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
7ML19985AB01 OCM III 90
CIRCULAR AREA X VELOCITY
h
transducer
*
**
* This dimension should be at least 15 cm (6") shorter than
the blanking value, P47.
** The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 91
GULL-WING AREA X VELOCITY, P3 = 18
‘U’ parameters required * ‘U’ parameters calculated **
U0 = channel base width b U4 = area (h)
U1 = lower angle alpha (α)
U2 = upper angle beta (β)
U3 = transition height ht
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
7ML19985AB01 OCM III 92
GULL WING AREA X VELOCITY
transducer *
V
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 93
EGG-SHAPED AREA X VELOCITY, P3 = 19
‘U’ parameters listed * ‘U’ parameters calculated **
U0 = top radius R U3 = area (h)
U1 = bottom radius r
U2 = axial displacement d
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
Reference
ABSOLUTE CALCULATION, P4 = 0¤
For flows that can be calculated by the equation:
q = 1/1000 x A x v
where : q = flow rate in l/sec
v = flow velocity in cm/sec
RATIOMETRIC CALCULATION, P4 = 1¤
For flows that can be calculated by the equation:
q = qcal x A/Acal x v/vcal
where : q = flow rate
qcal = flow rate at hcal
A = cross sectional area of flow
Acal = cross sectional area of flow at hcal
v = flow velocity
¤ Refer to Operation \ Flow Calculation.
7ML19985AB01 OCM III 94
EGG-SHAPED AREA X VELOCITY
transducer *
standpipe **
* This dimension should be at least 15 cm (6") shorter than
the blanking value, P47.
** The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 95
UNIVERSAL AREA X VELOCITY, P3 = 20
Arbitrary area is typically used when the primary element and/or its flow do not fit any
of the primary elements covered by P3. There is no user difference between absolute
and ratiometric calculations P4.
The flow curve is characterized by entering the head (Aeven) and area (Aodd)
ordinates for the number of data points (n, 4 to 16) over the flow range. The first
point (A0,A1) generally being at 0 head and the last point (A2n-2,A2n-1) generally being
at maximum head .
‘U’ parameters required * ‘U’ parameters calculated **
U0 = number of data points (n, 4 to 16) U1 = area (h)
Aeven = head
Aodd = area
*obtain from manufacturer’s specifications.
**calculated by OCM-3. May be viewed by accessing ‘U’ parameter.
e.g. typical open channel transducer *
* The transducer must be above the maximum head by at least the
blanking value, P47.
7ML19985AB01 OCM III 96
UNIVERSAL AREA X VELOCITY
U0 = 8
A0 = 0 head, point 1
A1 = 0.0 area, point 1
A2 = 0.05 head, point 2
A3 = 0.03 area, point 2
A4 = 0.1 head, point 3
A5 = 0.06 area, point 3
A6 = 0.15 head, point 4
A7 = 0.09 area, point 4
A8 = 0.25 head, point 5
A9 = 0.18 area, point 5
A10 = 0.45 head, point 6
A11 = 0.35 area, point 6
A8 = 0.70 head, point 7
A9 = 0.59 area, point 7
A8 = 1.00 head, point 8
A9 = 0.89 area, point 8
For best accuracy concentrate data points where changes in flow are the greatest.
A odd
A even
Head
Area
7ML19985AB01 OCM III 97
7ML19985AB01 OCM III 98
MAINTENANCE
The OCM-3 requires very little maintenance due to its solid-state circuitry. However, a
program of periodic preventative maintenance should be initiated. This should include
regular inspection, general cleaning, overall system performance checks and standard
good housekeeping practices.
A periodic inspection of the transducer is recommended, at which time any build-up of
material on the face should be removed.
The enclosure should be cleaned using a vacuum cleaner and a clean, dry brush.
For battery replacement refer to Installation / Installing the Memory Back-up Battery.
7ML19985AB01 OCM III 99
ERROR CODES
Error Code Listing
1 number underflow
2 number overflow
3 divide error
4 bad argument
5 invalid parameter
6 system is locked
7 head exceeds BS-3680 spec
8 must use ratiometric
9 invalid angle size
10 invalid selection
11 value is view-only
12 characterizer in use
13 feature not available
14 need whole number
15 invalid date
16 invalid time
20 can’t zero auxiliary device
21 b must be greater than R-r
7ML19985AB01 OCM III 100
COMMUNICATIONS
The OCM-3 provides serial communication either through Milltronics proprietary
bipolar current loop or industry standard RS-232. Communication can be used to
provide a video or paper printout of OCM activity. It can also be used to provide
remote programming and retrieval of the data log, from devices such as computers
and PLCs.
When using the bipolar current loop, communication runs of up to 1,500 m can be
achieved, as opposed to the limited runs of 15 m using RS-232. By terminating the
bipolar current loop with a Milltronics CVCC, the communication format is then
converted to RS-232.
* Milltronics OCM -3 Utilities Software available
** provides conversion to RS -232 or 422
RS-232
customer’s
computer *
CVCC **
optional parallel printer
serial printer
customer’s
computer *
bipolar current loop
OCM - 3
site number
(P39 )
7ML19985AB01 OCM III 101
Milltronics provides a standard Utilities software package, for convenient
communication between an IBM PC compatible computer and the OCM-3. In addition,
the user may opt to develop his own custom software program to perform tasks suited
to his specific needs.
Protocol
The protocol for the OCM-3 is as follows:
baud rate: set via P37
parity: none
stop bits: 1
word length: 8
The OCM-3 uses a three wire XON/XOFF serial communication link. When the
OCM-3’s receive buffer is near full, the OCM-3 sends an XOFF signal to tell the
sender of the near full condition.
If the sender is also using XON/XOFF, it will respond to the XOFF signal by
suspending its transmission.
Similarly, when the OCM-3 receive buffer is near empty, the OCM-3 sends an XON
signal to tell the sender that it is safe to resume sending.
The communication baud rate of the OCM-3 and its correspondent must be the same.
7ML19985AB01 OCM III 102
Interconnection
Bipolar Current
RS-232
IBM PC Computer Connection
refer to CVCC
instruction
manual for
connection to
computer
computer serial port
DB-9 connector
computer serial port
DB-25 connector
1234567
CVCC
TB1
+
-
-
C
O
M
M
O
N
T
R
A
N
S
M
I
T
R
E
C
E
I
V
E
+
S
H
E
I
L
D
T
X
D
T
X
D
S
H
L
D
+
-
S
H
L
D
1 2 34 5 67891011
OCM-3
TB1
T
X
T
X
+
R
X
R
X
+- -
BIPOLAR
I/O
CURRENT
O/P
CURRENT
O/P
7ML19985AB01 OCM III 103
Timed Print Out
The OCM-3 can be programmed to periodically print out OCM data (P34/35). A typical
print out will have the following format.
Time hh:mm:ss
Date dd/mm/yy
Site Number #
Head # units
Velocity*# units
Temperature # units
Flow Rate # units
Flow Total # units
*only for applications using velocity input
When the output is directed to a serial printer, a delay is inserted between each line to
allow the printer time to print each line before another is sent. In that way, the simplest
of printers may be used without need of XON/OFF or hardware handshaking; only a
three wire connection is required. The printer must be at least 40 columns wide. The
OCM-3 sends text in upper and lower case. The printer must support both upper and
lower case or else treat lower case as if it had been sent in upper case.
The printing interval must divide evenly into the selected units of time for printing to
occur at regular intervals.
e.g. P34 = 1, printer mode set for interval in minutes
P35 = 7, print interval set for 7 minutes
Printing starts at 7 minutes after the hour and will occur every
7 minutes thereafter until 56 minutes into the hour. The next
print out would not occur until 7 minutes into the next hour.
Since the port used for communication is the same as used for normal serial
communication, a software switch controls whether or not the display is sent out on
the serial port. The switch is controlled by typing ’v’ to allow data transmission or ’w’ to
stop it. The Milltronics printer emulation program does this automatically.
If the OCM-3 is connected to a computer programmed for printer emulation, the
computer will receive the print out data and display it on the video terminal (refer to
Milltronics Utilities Software).
7ML19985AB01 OCM III 104
Milltronics Utilities Software Disk
The Milltronics Utilities Software expands the human interface capabilities of the
OCM-3 as compared to that provided by the simple use of the infra-red programmer.
Utilities Software Programmer
- remote OCM-3 programming - local programming
- remote OCM-3 display - local display
- saving OCM-3 program parameters
- retrieving log data
- creating spread sheet data log file
- creating ASCII text data log file
- emulating serial printer
- graphic flow rate display
7ML19985AB01 OCM III 105
The OCM-3 Utilities software provided by Milltronics uses XON/XOFF to ensure
communication reliability. The software is written to be executed on an IBM PC
compatible computer.
The standard keyboard emulates the OCM-3 programmer. Pressing the keys
corresponding to those displayed on the programmer will activate the same function
(see Start Up\Keypad). In addition, special functions are provided using the ’w’ and ’v’
keys found on keyboard.
For additional information, refer to the ’README.DOC’ file provided on the disk.
W V
7ML19985AB01 OCM III 106
Custom Programming and Third Party Communication Program
Users who wish to write their own software to communicate with the OCM-3 are urged
to implement a fully buffered (interrupt driven) serial link incorporating XON/XOFF.
Some users however, will not have the capacity for such an undertaking. Those users
may still communicate with the OCM-3 using the less sophisticated communication
capabilities provided by such high level languages as Basic, Pascal or C. The only
restriction imposed by using a system that does not use XON/XOFF, is that the user
must insure that he does not send long streams of commands to the OCM-3 without
pausing periodically to allow the OCM-3 time to process them.
Most users who wish to write their own software to communicate with the OCM-3 will
do so for a specific purpose. An example would be to create a customized data log.
For this, the user will want that only the numeric values be returned, and none of the
descriptive information.
To achieve this, the OCM-3 provides a secondary command parser which is accessed
when the OCM-3 receives a command enclosed by ‘/’. When the leading ‘/’ is detected
by the primary parser, the OCM-3 diverts the message to the secondary parser. The
secondary parser remains in control until it receives the trailing ‘/’.
If the trailing ‘/’ is not received within a few seconds, the secondary parser is aborted
and control is reverted to the primary parser automatically.
The OCM-3 response message to a command to the secondary parser is a sequence
of ASCII characters terminated by an ASCII carriage return (hex 0D) and an ASCII
line feed (hex 0A). All system parameters and most other responses are floating point
numbers with a maximum of 6 decimal places.
e.g. typical OCM-3 response
display value message
0 0.000000
99.123 99.123000
7ML19985AB01 OCM III 107
The following is a list of commands for the secondary parser:
Command Response
/a#/ the content of a#, where: a = A, D*, F, P and U
# = 0 through 9
e.g. /P5/ the content of P5
*D parameters are the only parameters which may be altered through the
secondary command parser (which bypasses the security parameter F0).
This may be useful, for example, in periodically reading and then resetting
the short total, ‘D2’. The protocol for altering the value of a D parameter via
the secondary parser is:
/dn=#/ where: n is parameter number
# is the value stored in the parameter
e.g. /d4=50/, this sets the minimum flow rate to 50 for D4
/t0/ totalizer value, similar to that of the ‘Flow and Total’
(F2) display, except that the multiplier is not displayed
/t1/ totalizer value, returned as a floating point number with
a maximum of 6 decimal places, modified to include the
effect of the totalizer multiplier.
e.g. if the OCM-3 display shows 00005678 x 100, the
response would be 567800.000000
/t2/ returns the current 24 hour time: hh:mm:ss
/t3/ returns the current date: dd/mm/yy
/f/ returns the current flow rate
this is similar to the OCM-3 parameter F2 display, however it
is not subject to truncation to less than 6 decimal places.
7ML19985AB01 OCM III 108
/j/ returns a code indicating the relay status
code relay
123
0000
1100
2010
3110
4001
5101
6011
7111
/l/ start data log down load.
/l1.dd.mm.yyyy/ data log down load - start date
/l2.dd.mm.yyyy/ data log down load - end date
/l3/ stop data log down load
7ML19985AB01 OCM III 109
Modem Communication
Communication with the OCM-3 over an answer back telephone modem is relatively
straight forward. For modem communication over conventional telephone lines, a
maximum of 1200 or 2400 baud is recommended. Generally, a lower baud rate is
more reliable on noisy lines. Modem should be self answering and data checking
capability turn on.
The Milltronics Utilities software can be run via modem. In addition the Terminal
Emulation program of the Utilities software package can be used to send control
sequences directly to the modem.
The remote modem is defined as the modem connected to the OCM-3. The local
modem is defined as the modem connected to the computer.
It should be noted that the modem responses listed in the following discussion serve
only to typify what is presently common in current field of RS-232 communication.
OCM - 3
C
O
M
R
X
D
T
X
D
RS 232
I/O
11
2
37
OCM-3
TB-1 12 13
remote modem
local modem
computer
standard modem
cable
telephone lines
modem
DB-25 connector
7ML19985AB01 OCM III 110
Considerations
- set the ’cold start’ (F12) default baud to 1200 by removing jumper J1 on board A.
- set both modems and the OCM-3 baud rates to 1200.
- set the remote modem to operate in the ’answer back’ mode.
Refer to modem’s user manual.
Communication
- select serial programming link with OCM-3, from the utilities menu. See Milltronics
Utilities Software Disk.
The computer screen will display the letters ’v’. These would normally
have gone to the OCM-3 to ask it to send its display, but the modem
will have returned it to the screen instead.
Establishing Communication
- type the following:
ATD and the telephone number of the remote modem, then press ‘ENTER’.
The modem will dial the number you have entered. When the local
modem establishes contact with the remote modem, the local modem
sends a message to the screen (typical).
CONNECT
- press the ‘v’ and ‘ENTER’ keys to turn on the OCM-3’s display-to-serial channel.
The OCM-3 is now on line and communication can be carried out. The user
may escape to the main menu of the Utilities software and select another
program if so desired.
To close the communication, return to the Terminal Emulation program.
7ML19985AB01 OCM III 111
Ending Communication
- type W to break OCM-3 communication with the modem*. The computer screen
will display a flashing message ‘OCM-3 muted’.
- type: +++ (not displayed on the screen) and then press ENTER
This will cause both modems to switch to the ‘command’ mode. The local
modem sends a message to the screen (typical).
OK
- type: ATH and press the ENTER key.
Both modems will hang up.
The local modem sends a message to the screen (typical).
OK
* If the W is not sent, the OCM-3 and its modem will still be in communication.
This may result in the OCM-3 modem being unable to answer calls successfully;
depending on the type of modem. OCM-3 software, 3.26 or later, averts this problem
by automatically breaking communication between the OCM-3 and its modem
after 15 minutes.
■
7ML19985AB01 OCM III 112
*7ml19985AB01* Rev. 1.0
www.siemens.com/processautomation
Siemens Milltronics Process Instruments Inc.
1954Technology Drive, P.O. Box 4225
Peterborough, ON, Canada K9J 7B1
Tel: (705) 745-2431 Fax: (705) 741-0466
Email: techpubs.smpi@siemens.com
Siemens Milltronics Process Instruments Inc. 2005
Subject to change without prior notice
Printed in Canada
