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MPM_DMR20-4/20.A01 Page 1 of 5
FEATURES
High-quality, 20-turn, span (gain) and zero (offset)
SIMPLIFIED SCHEMATIC DIAGRAM
For full details go to:
http://www.murata-ps.com/en/support/rohs-
compliance.html
Murata’s new DMR20-4/20 loop-powered digital process monitors feature a large,
easy-to-read, bright LED display. All operating power is derived directly from the
current loop itself—no external power source is required! The large, 0.30 [7.6 mm]
digits exhibit uniform intensity over the entire 4-20 mA operating range. Unlike other
loop-powered LED displays, the total maximum loop voltage drop for the red LED
model is 2.5V! Users no longer have to settle for difficult-to-read LCD displays in
loop-powered applications.
Both gain (span) and offset (zero) adjustments are performed with on-board,
precision, 20-turn potentiometers. All decimal-point and range-change selections
are made on a six-position DIP switch featuring vibration-resistant, gold-plated
contacts. Unlike competitive meters, there are no jumpers or solder gaps to open
or close. Connections to the current loop are made via a reliable, two-position,
screw-type terminal block.
The DMR20-4/20’s DIP-switch and potentiometers accommodate hundreds of
different input-current/output-reading combinations. This versatility eliminates the
need to order more costly, long-lead-time customs meters in applications in which
several different-range meters are required. The round plastic housing fits standard
1.20” [30.5mm] panel cutouts. An EPDM rubber gasket and hex nut simplify
installation and provide IP67/NEMA 6 protection to environmental dirt and moisture.
2.5V maximum loop-drop (125 Ω burden) for red LED model!
Self-powered directly from 4-20 mA current loop, no external
power source needed
Fits round 1.20 inch [30.5 mm] cutouts; less than 1.00 inch
[<25.4 mm] behind-the-panel depth
Easy-to-read, 0.30 inch [7.6 mm] high LED digits with excellent
display brightness; available in red or green LEDs
Supplied with EPDM rubber gasket and hex nut
High-quality, 20-turn, span (gain) and zero (offset) adjustments
Gold-plated DIP-switch for range and decimal points: Reliable
screw-terminal input connections
Rugged, polycarbonate, one-piece package
Protected against dust and water submersion to IP67/NEMA 6
DMR20-4/20 Series
Loop-Powered, 4-20 mA LED Display Process
Monitors with 2.5V Loop Drop
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MPM_DMR20-4/20.A01 Page 2 of 5
DMR20-4/20 Series
Subminiature 4-20 mA Loop-Powered
3½ Digit LED Process Monitors
Performance/Functional Specifications
Typical at TA = +25°C, unless otherwise noted.
OPERATING AND SETUP INSTRUCTIONS
DMR20-4/20S (Unipolar Reading Model)
As shipped, the DMR20-4/20S is factory calibrated to read “000” for a
4 mA input and “1000” for a 20 mA input. The following worst-case
procedure assumes the DMR20-4/20S is completely misadjusted, i.e.,
both potentiometers and the DIP switches are randomly set .When
performing DIP-switch settings, be sure the DIP switch’s small
actuators are firmly engaged in their fully-ON or fully-OFF positions.
1.
Set R7 (full scale span/gain adjust) and R3 (zero/offset adjust) fully
counterclockwise, roughly 22 turns, and set SW1-SW6 to OFF.
2.
Select DIP switch setting #2 in Table 1.
3.
Apply a precision 4 mA input to TB1 with proper polarity, and adjust
R3 until the meter’s display reads “000.”
4.
Apply a precision 20 mA input and adjust R7 until the meter’s display
reads “1000.” Repeat steps 3 and 4 to make sure the adjustments
do not affect one another.
5.
If required, select the appropriate decimal point by setting SW1 and
SW2 per the settings shown in Table 3.
NOTE: If a display reading other than ”000” to ”1000” is
desired, refer to DIP–Switch Settings Table 1 below for SW3–
SW6 settings.
Table 1
DMR20-4/20S (Unipolar Model) DIP-Switch Settings
➀ The DMR20-4/20, using any of the DIP-switch settings described above, can
withstand overcurrents, including those resulting from accidental reverse-polarity
connections, up to ±40 mA without sustaining any damage.
➁ Because DMR20-4/20 loop-powered meters employ active circuitry to convert
the loop current into a voltage; the meters’ effective series impedance varies in a
manner that maintains the loop voltage drop relatively constant over the full 4-to-
20 mA current range. Listed input impedance specification applies at 20 mA with
all DIP switches set to OFF.
➂ When looking up DIP-switch settings in the following Tables and the desired
display readings can be achieved with either of two different settings, using
the higher setting # will produce less sensitive offset (R3) and span (R7)
adjustments. Please keep in mind that the accuracy specification of ±2 counts
means it may not always be possible to obtain the exact desired display
reading.
Ordering Information
DMR20-4/20S-R-C Unipolar, loop-powered red LED meter
DMR20-4/20S-G-C Unipolar, loop-powered green ED meter
DMR20-4/20B-R-C Unipolar, loop-powered red LED meter
Note: An M30 x 1.5 nylon metric hex nut and EPDM sealing
gasket are supplied with each meter. The “-C” suffix indicates
RoHS compliance
4 mA
20 mA
SW3
SW4
SW5
SW6
1
000
to 1200-1999
Off
Off
Off
Off
2
000
to 750-1350
On
Off
Off
Off
3
000
to 500-850
Off
On
Off
Off
4
000
to 350-600
Off
Off
On
Off
5
000
to 250-350
On
On
On
Off
6
000
to 150-250
On
Off
On
On
Examples (DMR20-4/20S-Unipolar Models)
1.
Desired display readings are:
4 mA = “0.00”
20 mA = “6.00”
Use DIP-switch setting #3 in Table 1 and enable decimal point DP2 by
setting SW1 to ‘On’ and SW2 to ‘Off’. Apply 4 mA and adjust R3 so
the display reads “0.00.” Apply 20 mA and adjust R7 so the display
reads “6.00.”
2.
Desired display readings are:
4 mA=“000”
20 mA =“800”
Use DIP-switch setting #2 in Table 1. Apply 4 mA and adjust R3 so
the display reads “000.” Apply 20 mA and adjust R7 so the display
reads “800.” For these display readings, no decimal points are used
so set SW1 and SW2 both to On.
Display Readings
Current Loop Input
Min.
Typ.
Max.
Units
Full Scale Input Range
➀
+4
–
+20
mA
Input Impedance
➁
–
175
Ω
Loop Voltage Drop - Red LED
➁
–
2.2
2.5
Volts
Loop Voltage Drop - Green LED
➁
3.2
3.5
Volts
Overcurrent Protection
➀
–
–
±40
mA
Performance
Sampling Rate
2.5 readings per second
Accuracy (1 minute warm-up)
±0.05% FS ±2 Count
Temperature Drift
(0 to +60°C)
–
±0.15
±0.3
Cnts/°C
Display
Display Type and Size
3½ digit, 0.30” / 7.6 mm high red LED
Polarity Indication
“–” for negative reading
Overrange Indication
“–1 “ for
negative Vin
“1 “
for positive Vin
Physical/Environmental
Operating Temperature
0
–
+60
°C
Storage Temperature
–40
–
+75
°C
Humidity (non-condensing)
0
–
85
%
Case Material
Polycarbonate
Weight
0.65 ounces (18.5 grams)
Panel Knockout Tools:
DMR20-1-KP 1.22” [30.9 mm] punch (no keying notch)
DMR20-2-KP 1.21” [30.7 mm] punch with 4 keying notches
DMR20-3-KP Keyway Punch tool
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MPM_DMR20-4/20.A01 Page 3 of 5
DMR20-4/20 Series
Subminiature 4-20 mA Loop-Powered
3½ Digit LED Process Monitors
3.
Desired display readings are:
4 mA =.”000”
12 mA =.”250”
This example is not as straightforward as the previous two. Notice that
12 mA is exactly halfway between 4 mA and 20 mA. If we assume that
the input could go up to 20 mA, the display reading would then be: 2
x. 250 or .”500.” From Table 1 we can now select DIP-switch setting
#4 and enable DP1 by setting SW1 to Off and SW2 to On. Apply 4 mA
and adjust R3 so the display reads ”000.” Apply 12 mA and adjust R7
so the display reads ”250.”
DMR20–4/20B (Bipolar Reading Model)
The DMR20-4/20B’s zero-offset circuit differs from the unipolar ‘S’ model
described above in that with the ‘B’ model, a half-scale 12 mA input is
normally set to display ”000.” Therefore, all of the DIP-switch settings in
Table 2 assume a reading of “000” is desired with a 12 mA input.
When configuring the DMR20-4/20B for the first time, or when selecting a
new range, set both R3 and R7 fully counterclockwise (roughly 22 turns)
to their minimum offset/minimum-span positions, respectively. Then
select the desired readings from Table 2 and configure DIP-switches
SW3, SW4, SW5, and SW6 accordingly.
The procedure below illustrates how to calibrate the DMR20-4/20B to its
factory-calibrated readings of “–1000” with a 4 mA input and “1000” with
a 20 mA input. When performing DIP-switch settings, be sure the DIP-
switch’s small actuators are firmly engaged in their fully-ON or fully-OFF
positions.
1.
Set both R3 and R7 fully counterclockwise.
2.
Select DIP-switch setting #1 from Table 2.
3.
Apply a precision 12 mA input and adjust R3 until the meter’s
display reads “000.”
4.
Apply a precision 20 mA input and adjust R7 until the meter’s
display reads “1000.”
5.
Apply a precision 4 mA input and the display should read “–1000.”
Repeat steps 3 and 4 to make sure the two adjustments did not affect
one another.
Table 2
DMR20-4/20B (Bipolar Model) DIP-Switch Settings
Examples (DMR20-4/20B-Bipolar Model)
1.
Desired display readings are:
4 mA=“–1.00”
20 mA =“1.00”
Use DIP-switch setting #5 in Table 2 and enable decimal point DP2 by
setting SW1 to ‘On’ and SW2 to ‘Off’. Apply 12 mA and adjust R3 so
the display reads “0.00.” Apply 20 mA and adjust R7 so the display
reads “1.00.” Apply 4 mA and verify that the display reads “–1.00,”
readjust R3 and R7 if necessary.
2.
Desired display readings are:
4 mA=“–450”
20 mA =“450”
Use DIP-switch setting #2 in Table 2. Apply 12 mA and adjust R3 so
the display reads “000.” Apply 20 mA and adjust R7 so the display
reads “450.” Apply 4 mA and verify that the display reads “–450.”
Repeat adjustment procedure if necessary. For these display
readings, no decimal points are used, so set SW1 and SW2 to On.
3.
Desired display readings are:
4 mA=“–650”
20 mA =“650”
Select DIP-setting # 1 in Table 2. Apply 12 mA and adjust R3 so the
display reads “000.” Apply 20 mA and adjust R7 so the display reads
“650.” Apply 4 mA and verify that the display reads “–650.” Repeat
adjustment procedure if necessary. For these display readings, no
decimal points are used, so set SW1 and SW2 to On.
Table 3
Decimal Point Settings (All Models)
SW1
SW2
Decimal Point
Off
Off
DP3
On
Off
DP2
Off
On
DP1
On
On
None
4 mA
12 mA
20 mA
SW3
SW4
SW5
SW6
1
–600 to –1000
000
600 to 1000
Off
Off
Off
Off
2
–400 to –600
000
400 to 600
On
Off
Off
Off
3
–250 to –400
000
250 to 400
Off
On
Off
Off
4
–150 to –250
000
150 to 250
Off
Off
On
Off
5
–100 to –150
000
100 to 150
On
Off
On
On
6
–70 to –100
000
70 to 100
Off
On
On
On
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MPM_DMR20-4/20.A01 Page 5 of 5
DMR20-4/20 Series
Subminiature 4-20 mA Loop-Powered
3½ Digit LED Process Monitors
MECHANICAL SPECIFICATIONS AND RECOMMENDED PANEL CUTOUT
Murata Power Solutions, Inc.
11 Cabot Boulevard, Mansfield, MA 02048-1151 U.S.A.
ISO 9001 and 14001 REGISTERED
This product is subject to the following operating requirements
and the Life and Safety Critical Application Sales Policy:
Refer to: http://www.murata-ps.com/requirements/
Murata Power Solutions, Inc. makes no representation that the use of its products in the circuits described herein, or the use of other
technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein do not imply
the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifications are subject to change without
notice. © 2015 Murata Power Solutions, Inc.
http://www.murata-ps.com/en/3d/meters.html
Available Panel Knockout Tools
DMR20-1-KP 1.22” [30.9 mm] punch (no keying notch)
DMR20-2-KP 1.21” [30.7 mm] punch with 4 keying notches
DMR20-3-KP Keyway Punch tool
Recommended Terminations at TB1
WIRE SIZE: 18 to 26 AWG (Solid or stranded)
STRIPPING LENGTH: 0.20” [5.1 mm] Nominal
