DMS-20LCD-4/20 Series
4-20mA Input Loop-Powered Ultra-Low 1.8V Loop Drop
3½ Digit LCD Display Process Monitors
MPM_DMS20LCD-420.C01 Page 1 of 6
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SIMPLIFIED SCHEMATIC DIAGRAM
The DMS-20LCD-4/20 Series produces the lowest loop voltage-drop of any comparably
priced, 4-20mA input, 3½ digit LCD-display process monitors: 1.8V typical, 2.0V max. This
super-low drop means its nominal loop resistance (burden) is less than 100 Ohms! All op-
erating power is derived solely from the 4-20mA loop current—no separate power source
is required! The simple 2-wire hookup allows the DMS-20LCD-4/20 Series to be connected
anywhere in the loop
All decimal-point and range-change selections are made via a six-position DIP
switch featuring vibration-resistant, gold-plated contacts—there are no jumpers or solder
gaps to ever open or close. Both gain (span) and offset (zero) adjustments are performed
with precision, 20-turn potentiometers. Three different models are available for unipolar,
bipolar, and positive display reading applications. The DMS-20LCD-4/20’s DIP switch and
adjustment potentiometers can accommodate literally hundreds of different input-current/
output-reading combinations. And, connections to the current loop are made via a reliable,
two-position, screw-type terminal block.
The DMS-20LCD-4/20 Series’ subminiature package houses a large, 0.37"/9.4mm
high digits, LCD display that can be read in virtually all lighting conditions—including direct
sunlight. An optional bezel assembly, featuring screw fasteners and a rubber seal, simplifi es
panel mounting and provides excellent resistance to environmental dust and moisture.
All these outstanding features combine to make the DMS-20LCD-4/20 Series the perfect
meters for OEM 4-20mA current-loop process monitoring instrumentation.
FEATURES
Super-low loop drop: 1.8V typical, 2.0V max.
Self-powered, no separate supply required
Unipolar, Bipolar, and Positive Reading Models
Subminiature package—Less than 0.90" behind-the-
panel depth
Large, 0.37"/9.4mm high, sunlight-viewable
LCD display
Non-interacting gain (span) and offset (zero) 20-turn
potentiometers
DIP-switch selectable range and decimal points
Hundreds of different input/readout combinations
Vibration-resistant package; reliable screw-terminal
input connections
DATA
3½ DIGIT A/D
CONVERTER
DC/DC
CONVERTER
REFERENCE
CIRCUIT
BAND-GAP
DIP SWITCHES
ZERO
ADJUST GAIN
2
ADJUST
13
CURRENT TO
VOLTAGE
CONVERTER
+5V –5V
DP3DP2DP1
R3 R7
12
TB1
+–
LOOP INPUT
ON
ON
1
1
12
23
34
46
6
5
56
5
Performance/Functional Specifi cations
Typical at TA = +25°C, unless otherwise noted.
➀ The DMS-20LCD-4/20, using any of the DIP-switch settings described above,
can withstand overcurrents, including those resulting from accidental reverse-
polarity connections, up to ±40mA without sustaining any damage.
➁ Because Murata Power Solutions' DMS-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 constant
over the full 4-to-20mA current range. Listed impedance specifi cation applies at
20mA.
DMS-20LCD-4/20S-C Unipolar reading, loop-powered LCD meter
DMS-20LCD-4/20B-C Bipolar reading, loop-powered LCD meter
DMS-20LCD-4/20P-C Positive reading, loop-powered LCD meter
DMS-BZL3-C Bezel assembly
DMS-BZL4-C Bezel assembly with sealing gasket
DMS-20-CP Panel cutout punch
A panel-mount retaining clip is supplied with each model.
1. Desired display readings are:
4mA ="0.00"
20mA = "6.00"
Use DIP-switch setting #3 in Table 1 and enable decimal point DP2 via
SW5. Apply 4mA and adjust R3 so the display reads "0.00". Apply
20mA and adjust R7 so the display reads "6.00".
2. Desired display readings are:
4mA = "000"
20mA = "800"
Use DIP-switch setting #2 in Table 1. Apply 4mA and adjust R3 so the
display reads "000". Apply 20mA and adjust R7 so the display reads
"800". For these display readings, no decimal points are used. Set
SW4, SW5 and SW6 to OFF.
3. Desired display readings are:
4mA = ".000"
12mA = ".250"
This example is not as straightforward as the previous two. Notice that
12mA is exactly halfway between 4mA and 20mA. If we assume that
the input could go up to 20mA, 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 via SW4. Apply 4mA and adjust R3 so the display
reads ".000". Apply 12mA and adjust R7 so the display
reads ".250".
Examples (DMS-20LCD-4/20S-Unipolar Model)
DMS-20LCD-4/20S (Unipolar Reading Model)
As shipped, the DMS-20LCD-4/20S is factory calibrated to read "000"
for a 4mA input and "1000" for a 20mA input. The following worst-case
procedure assumes the DMS-20LCD-4/20S is completely mis-adjusted,
i.e., both potentiometers and the DIP switches are randomly set. When
Current Loop Inputs Min. Typ. Max. Units
Full Scale Input Range ➀+3.8 – +20.4 mA
Input Impedence ➁– 80 100 Ω
Voltage Drop ➁– 1.8 2.0 Volts
Overvoltage Protection ➀– – ±40 mA
Performance
Sampling Rate 2.5 reading per second
Accuracy (1 minute warm-up): ±0.05%FS ±1 Count
Temperature Drift (0 = +60°C) – ±0.15 ±0.3 Cnts/°C
Display
Display Type and Size 3½ digit, 0.37"/9.4mm high LCD
Polarity Indication "–" for negative readings
Overrange Indication "–1_ _ _ " for negative inputs
"1_ _ _ " for positive inputs
Physical/Environmental
Operating Temperature 0 – +60 °C
Storage Temperature –20 – +75 °C
Humidity (non-condensing) 0 – 95 %
Case Material Polycarbonate
Weight 0.6 ounces (17 grams)
Ordering Information
123456
ON
123456
ON
123456
ON
performing DIP-switch settings, be sure the DIP switch's small actuators
are fi rmly engaged in their fully-ON or fully-OFF positions.
1. Set R7 (full scale span/gain adjust) and R3 (zero/offset adjust) fully
clockwise, roughly 22 turns, and place SW1-SW6 to OFF.
2. Select DIP switch setting #2.
1. Set R7 (full scale span/gain adjust) and R3 (zero/offset adjust) fully
clockwise, roughly 22 turns, and place SW1-SW6 to OFF.
2. Select DIP switch setting #2.
3. Apply a precision 4mA input, with proper polarity, and adjust R3 until
the meter's display reads "000".
4. Apply a precision 20mA 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. Select the appropriate decimal point by setting SW4, SW5 or SW6 to
ON (DP1, DP2 or DP3 respectively).
NOTE: If a display reading other than "000" to "1000" is desired,
refer to DIP–Switch Settings Table 1 for SW1–SW3 settings.
DMS-20LCD-4/20 Series
4-20mA Input Loop-Powered Ultra-Low 1.8V Loop Drop
3½ Digit LCD Display Process Monitors
MPM_DMS20LCD-420.C01 Page 2 of 6
www.murata-ps.com/support
OPERATING AND SETUP INSTRUCTIONS
See www.murata-ps.com/dpm-availability for model-specifi c availability.
20mA and adjust R7 so the display reads "1.00". Apply 4mA and
verify that the display reads "–1.00", readjust R3 and R7 if necessary.
2. Desired display readings are:
4mA = "–450"
20mA = "450"
Use DIP-switch setting #2 in Table 2. Apply 12mA and adjust R3 so
the display reads "000". Apply 20mA and adjust R7 so the display
reads "450". Apply 4mA and verify that the display reads "–450".
Repeat adjustment procedure if necessary. For these display read
ings, no decimal points are used. Set SW4, SW5 and SW6 to OFF.
3. Desired display readings are:
4mA = "–650"
20mA = "650"
Notice that these readings can be obtained using either DIP-switch
setting #1 or DIP-switch setting #2 in Table 2. In situations like this
where DIP-switch settings overlap, less-sensitive R3/R7 adjustments
can be achieved if the higher DIP-setting # is selected (setting #2
in this example). Apply 12mA and adjust R3 so the display reads
"000". Apply 20mA and adjust R7 so the display reads "650". Apply
4mA and verify that the display reads "–650". Repeat adjustment
procedure if necessary.
DMS–20LCD–4/20B (Bipolar Reading Model)
The DMS-20LCD-4/20B's zero-offset circuit differs from the unipolar 'S'
model described above in that with the 'B' model, a half-scale 12mA input
is normally set to display "000". Therefore, all of the of the DIP-switch
settings in Table 2 assume a reading of "000" is desired with a 12mA input.
Display readings other than those shown in Table 2 are possible, contact
Murata Power Solutions for more information.
When confi guring the DMS-20LCD-4/20B for the fi rst time, or when select-
ing a new range, set both R3 and R7 fully clockwise (roughly 22 turns) to
their minimum offset/minimum-span positions, respectively. Then select
the desired readings from Table 2 and confi gure DIP-switches SW1, SW2,
and SW3 accordingly.
The procedure below illustrates how to calibrate the DMS-20LCD-4/20B
to its factory-calibrated readings of "–1000" with a 4mA input and "1000"
with a 20mA input. When performing DIP-switch settings, be sure the DIP-
switch's small actuators are fi rmly engaged in their fully-ON or fully-OFF
positions.
1. Set both R3 and R7 fully clockwise.
2. Select DIP-switch setting #1 from Table 2.
3. Apply a precision 12mA input and adjust R3 until the meter's display
reads "000".
4. Apply a precision 20mA input and adjust R7 until the meter's display
reads "1000".
5. Apply a precision 4mA input and the display should read "–1000".
Repeat steps 3 and 4 to make sure the two adjustments did not
affect one another.
Examples (DMS-20LCD-4/20B-Bipolar Model)
1. Desired display readings are:
4mA = "–1.00"
20mA = "1.00"
Use DIP-switch setting #5 in Table 2 and enable decimal point DP2 via
SW5. Apply 12mA and adjust R3 so the display reads "0.00". Apply
Display Reading SW1 SW2 SW3
4mA 20mA
1. 000 to 1050-1999 Off Off Off
2. 000 to 650-1350 On Off Off
3. 000 to 450-800 Off On Off
4. 000 to 300-500 Off Off On
5. 000 to 200-300 On On On
Table 1. DMS-20LCD-4/20S (Unipolar Model) DIP-Switch Settings ➂
Display Reading SW1 SW2 SW3
4mA 12mA 20mA
1. –600 to –1000 000 600 to 1000 Off Off Off
2. –350 to –650 000 350 to 650 On Off Off
3. –250 to –400 000 250 to 400 Off On Off
4. –150 to –250 000 150 to 250 Off Off On
5. –100 to –150 000 100 to 150 On On On
Table 2. DMS-20LCD-4/20B (Bipolar Model) DIP-Switch Settings ➂
DMS-20LCD-4/20P (Positive Reading Model)
The DMS-20LCD-4/20P’s Zero-Offset circuit is optimized to produce
positive readings at both 4mA and 20mA input levels. As shown in Table
3’s fi rst three columns, a 4mA input can be typically adjusted (using
R3, Zero/Offset Adjust) to display any positive reading between “000”
and “800”. The corresponding 20mA-input reading is then added to the
4mA offset as a differential whose magnitude is varied by adjusting R7
(Gain/Span Adjust).
The ‘Differential Range’ column in Table 3 lists the nominal differential
display-readings which can be obtained with R7 at, or very close to, its
full-clockwise, minimum span position. The Differential Range column can
be used as a guide when confi guring the meter for the majority of user
applications. Higher differential ranges are obtainable; however, the use of
higher differential readings results in correspondingly-lower positive read-
ings with 4mA inputs, that is, R3’s clockwise adjustment-range is reduced.
Example #3 below illustrates this concept. Please contact Murata Power
Solutions if there is any doubt as to whether or not the DMS-20LCD-
4/20P can be confi gured for your display readings requirements.
➂ When looking up DIP-switch settings in the 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 DMS-20LCD standard meter (from which the DMS-
20LCD-4/20 is derived) has an accuracy specifi cation of ±2 counts (max.). Thus,
it may not always be possible to obtain the exact desired display reading.
123456
ON
123456
ON
123456
ON
DMS-20LCD-4/20 Series
4-20mA Input Loop-Powered Ultra-Low 1.8V Loop Drop
3½ Digit LCD Display Process Monitors
MPM_DMS20LCD-420.C01 Page 3 of 6
www.murata-ps.com/support
Table 4. Decimal Point Settings
Examples (DMS-20LCD-4/20P-Positive Model)
1. Desired display readings are:
4mA = “650”
20mA = “950”
Use DIP-switch setting #4 in Table 3 since subtracting 650 from 950 yields
a differential value of 300. Apply 4mA and adjust R3 until the display reads
“000”. Apply 20mA and adjust R7 until the display reads “300” (the differen-
tial value previously calculated). Apply 4mA and adjust R3 until the display
reads “650”. Apply 20mA and verify that the display reads “950”.
2. Desired display readings are:
4mA = “4.00”
20mA = “19.99”
This example illustrates the DMS-20LCD-4/20P’s capability to display higher
differential readings than those indicated in Table 3. This example also
illustrates how the DMS-20LCD-4/20P can be used to display the output
levels of a 4-20mA loop transmitter with higher precision (0.01mA versus
0.1mA) than described above.
Subtracting 400 from 1999 yields a differential of 1599, a value not listed in
Table 3. However, use DIP-switch setting #1 in Table 3 since this setting has
the highest overall offset/span adjustment capabilities. Enable DP2 via SW5
then apply 4mA and adjust R3 so the display reads “0.00”. Apply 20mA and
adjust R7 so the display reads “15.99”. Apply 4mA and adjust R3 until the
display reads “4.00”. Apply 20mA and check to see that the display reads
“19.99” or just overranges (“1—“). Repeat adjustment procedure if neces-
sary.
Table 3. DMS-20LCD-4/20P (Pos. Reading) DIP-Switch Settings ➂
Differential Range 4mA Input 20mA Input
Display Reading SW1 SW2 SW3
SW4 SW5 SW6
DP1 DP2 DP3
1. 800-1400 900 1700 Off Off Off
2. 500-800 850 1350 On Off Off
3. 350-500 800 1150 Off On Off
4. 250-350 750 1000 Off Off On
5. 150-250 750 900 On On On
123456
ON
123456
ON
The fi rst step when confi guring the DMS-20LCD-4/20P for the fi rst time, or
when selecting a new range, is to set R3 fully counterclockwise and R7 fully
clockwise (roughly 22 turns) to their minimum offset/minimum span posi-
tions, respectively.
The next step is to calculate the required display differential-reading; this
is accomplished by subtracting the desired 4mA display reading from the
desired 20mA display reading, disregarding decimal points. Then, using the
calculated differential display-reading to select the appropriate DIP-switch
setting # from Table 3, confi gure DIP-switches SW1, SW2, and SW3 accord-
ingly. Make certain that the DIP-switch’s small actuators are fi rmly engaged
in their fully-ON or fully-OFF positions.
The procedure below describes how to calibrate the meter for an application
which the DMS-20LCD-4/20P easily accommodates: displaying the output
of a 4-20mA transmitter, that is, "04.0" with a 4mA input and "20.0" with a
20mA input.
1. Set R3 fully counterclockwise (minimum offset position) and R7 fully
clockwise (minimum differential span position), roughly 22 turns.
2. Subtract 040 from 200 to yield a differential value of 160; use
this value to select DIP-switch setting #5 in Table 3. Enable decimal
point DP3 by placing SW6 to the ON position.
3. Set the transmitter’s output to 4.0mA and carefully adjust R3 clockwise
until the meter’s display reads “000”.
4. Set the transmitter’s output to 20.0mA and adjust R7 counterclock-
wise until the meter’s display reads “16.0”.
5. Set the transmitter back to 4.0mA and slowly adjust R3 clockwise until
the display reads “04.0”. Reapply 20.0mA and the display should now
read “20.0”. Repeat steps 3, 4 and 5 to make sure the adjustments did
not affect one another.
DMS-20LCD-4/20 Series
4-20mA Input Loop-Powered Ultra-Low 1.8V Loop Drop
3½ Digit LCD Display Process Monitors
MPM_DMS20LCD-420.C01 Page 4 of 6
www.murata-ps.com/support
#2-56 INSERT
FRONT VIEW
0.156 (3.96) DEEP
1.280
(32.51)
0.187
(4.75)
RECOMMENDED DRILL AND PANEL CUTOUT DIMENSIONS
1.826 (46.38)
0.838
(21.29)
1.336 (33.93)
1.07
(27.18)
INTERNAL CORNER RADII:
0.032 (0.81) MAX.
0.145
(3.68)
0.116
(2.95)
1.626 (41.30)
0.093 (2.362) DIAMETER (4 REQUIRED)
ONLY WHEN USING OPTIONAL BEZEL ASSEMBLY
Figure 2. Typical DMS-20LCD-4/20 Connection Diagram
➀
Shown for illustrative purposes only, may not be present in all applications
A/D
PROGRAMMABLE LOGIC CONTROLLER
TRANSMITTER &
TRANSDUCER
INPUT
+
SIGNAL CONDITIONER
––
+–
+
Vsig
–
GAIN
DMS-20LCD-4/20
ZERO
+24V
4-20mA
+
–
4-20mA
+24Vdc
SUPPLY
+
R7
R3
(TB1-1)
(TB1-2)
BEZEL INSTALLATION
BEZEL
PANEL
RETAINING CLIP INSTALLATION
PANEL
DMS-20LCD-4/20 Series
4-20mA Input Loop-Powered Ultra-Low 1.8V Loop Drop
3½ Digit LCD Display Process Monitors
MPM_DMS20LCD-420.C01 Page 5 of 6
www.murata-ps.com/support
BEZEL INSTALLATION AND RECOMMENDED DRILL AND PANEL CUTOUT
MECHANICAL DIMENSIONS: Inches (mm)
TOLERANCES: 2 PL DEC ±0.02 (±0.51)
3 PL DEC ±0.010 (±0.254)
WIRE SIZE: 18 to 26 AWG
(Solid or stranded)
STRIPPING LENGTH: 0.20" (5.08mm)
DIP Front View
Switches
Gain/Span
Adjust
Adjust
Loop
Input
Back View
Zero/Offset
DP2
(SW5)
DP3
(SW6)
DP1
(SW4)
0.80
(20.3)
0.040
(1.02)
1.30
(33.0)
1.38
(35.1)
0.88
(22.4)
0.90
(22.9)
MADE IN USA
DMS-20LCD-4/20
R3
R7
12 1
2
2
23
3
36
6
6
4
4
45
5
5
+–
1
11
ON
ON
ON
12
DMS-20LCD-4/20 Series
4-20mA Input Loop-Powered Ultra-Low 1.8V Loop Drop
3½ Digit LCD Display Process Monitors
MPM_DMS20LCD-420.C01 Page 6 of 6
www.murata-ps.com/support
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. Specifi cations are subject to change without
notice. © 2015 Murata Power Solutions, Inc.
Murata Power Solutions, Inc.
11 Cabot Boulevard, Mansfi eld, 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/
MECHANICAL SPECIFICATIONS
