www.murata-ps.com
DMS-20LCD Series
3½ Digit, LCD Display Digital Panel Voltmeters
FEATURES
Lowest cost
Lowest power, 2mW
Subminiature size:
1.38" x 0.88" x 0.43"
35mm x 22mm x 11mm
Large (0.37"/9.4mm), enhanced-contrast LCD display
Epoxy-encapsulated, 12-pin DIP
or pc-board mountable
Panel
differential input voltage ranges
4
accuracy, ±1 count (±0.05%)
High
Single +5V supply or 9V battery
Low-battery annunciator
User-selectable decimal point placement
to +60°C temperature range
0
DMS-20LCD Series, 3½ Digit, LCD Display, Digital Voltmeters represent the ultimate
combination of low price, low power, small size and high performance in digital meters.
Epoxy encapsulated in a subminiature (1.38” x 0.88” x 0.43”), 12-pin DIP package, these
completely self-contained, fully operational meters offer a combination of ruggedness,
long-term reliability and component-like ease-of-use simply not available in any other
meters.
Incorporating a precision reference and a factory-calibrated, autozeroing A/D converter,
DMS-20LCD meters are extremely accurate (±1 count) and are only slightly larger than
their 0.37"/9.4mm, enhanced-contrast, LCD displays. All models incorporate a built-in
bezel and are easily mounted in either panels or pc boards. Both backlit and non-backlit
versions are available.
DMS-20LCD meters have 4 differential input voltage ranges (±200mV, ±2V, ±20V and
±200V) and a user-friendly input structure. Input impedance is a minimum 800k. CMRR
is typically 86dB with a CMV of ±2V. Non-inverting inputs are overvoltage protected to
±100V (±250V for the ±200V input model).
All DMS-20LCD meters operate from a single +5V supply (drawing 400µA) or a single
+9V supply/battery (drawing 230µA). All models have a low-battery ("B") annunciator and
feature autopolarity changeover and overrange indication.
Also available is an application/evaluation board (DMS-EB2) that plugs directly onto the
back of any DMS-20LCD allowing direct inputs for common applications such as 4-20mA
inputs, zero/gain adjust, decimal point location, and input voltage dividing.
SIMPLIFIED SCHEMATIC DIAGRAM
+5V
+5V SUPPLY/ 1
+BATTERY
–5V
N.C.
2
DC/DC
CONVERTER
3
V+
2
12
(–) INPUT LO
0.01μF
R2
1
R1
V–
≈+2.0V
909k
11
(+) INPUT HI
5V RETURN/ 3
–BATTERY
J1
0 Vdc
A/D
CONVERTER
10 ANALOG
COMMON
DATA
DP 3
4
9
N.C./BACKLIGHT
4
5
DP 2
+5V
8
REFERENCE OUT
6
DP 1
7
REFERENCE IN
1
R2 is not used on ±200mV (-0) models or ±2V (-1) models.
R2 = 100k on ±20V (-2) models and 9.1k on ±200V (-3) models.
Only used on ±200mV (-0) and ±2V (-1) models.
3
DC/DC converter is not used on 9V-powered models,
J1 is connected.
Used on backlit models only.
N.C. for non-backlit models.
2
4
For full details go to
www.murata-ps.com/rohs
www.murata-ps.com/support
MPM_DMS20LCD.C01
Page 1 of 6
DMS-20LCD Series
3½ Digit, LCD Display Digital Panel Voltmeters
Performance/Functional Specifications
Typical at T
A
= +25°C and supply voltage = +5V (using the single-ended input
circuit) or +9V (using the differential input circuit), unless otherwise noted.
Analog Inputs
Full Scale Input Range:
DMS-20LCD-0
DMS-20LCD-1
DMS-20LCD-2
DMS-20LCD-3
Input Impedence:
DMS-20LCD-0, -1
DMS-20LCD-2, -3
Overvoltage Protection
➀
DMS-20LCD-0, -1, -2
DMS-20LCD-3
Common Mode Voltage Range
CMRR
(dc to 60Hz)
Control Inputs
➁
Decimal Pt. Placement
(Pins 4-6)
Functionality
Logic Compatibility
Backlight
(Pin 9)
Performance
Sampling Rate
Accuracy (1 minute warm-up):
DMS-20PC-0 (Vin = +0.19V)
DMS-20PC-1 (Vin = +1.9V)
DMS-20PC-2 (Vin = +19V)
DMS-20PC-3 (Vin = +190V)
Zero Reading
(Vin = 0 Volts)
Temperature Drift
(0 = +60°C)
–
–
–
–
“–001”
–
±1
±1
±2
±2
“000”
±0.2
±2
±2
±3
±3
“001”
±0.4
Cnts/°C
Counts
Counts
Counts
Counts
Accessories:
DMS-20-CP
DMS-BZL3-C
DMS-BZL4-C
DMS-EB2-C
2.5 reading per second
Tie to pin 3 to activate
Tie to pin 3 to activate
TTL (on 5V-powered models)
Tie to pin 3 to turn on backlight
Input Range:
0
= ±200mV
1
= ±2V
2
= ±20V
3
= ±200V
–
–
–
–
–
–
–
86
±100
±250
±2
–
Volts
Volts
Volts
dB
–
–
–
–
–
100
0.8
1000
1
–
–
M
M
±200
±2
±20
±200
–
–
–
–
mV
Volts
Volts
Volts
Min.
Typ.
Max.
Units
Physical/Environmental
Operating Temperature
Storage Temperature
Humidity (non-condensing)
Case Material
Weight
0
–20
0
–
–
–
+60
+75
95
°C
°C
%
Polycarbonate
0.4 ounces (11 grams)
➀
Applies for transient or continuous overvoltages applied to (+) INPUT HI
(pin 11) with (–) INPUT LO (pin 12) properly connected. Pin 12 is not
overvoltage
protected (see Figure 1). Voltages applied to pin 12 should not exceed the
supply voltage.
➁
Listed spec applies to 5V-powered models only. For 9V-powered models, both
(–) INPUT LO (pin 12) and (+) INPUT HIGH (pin 11) must always be at least
1.5V above –BATTERY (pin 3) and at least 1.5V below +BATTERY (pin 1).
➂
Technical Notes.
See
Ordering Information
DMS-20LCD - 1 - 5
-C
Add -C for RoHS
Leave blank for standard
models.
Add
B
for backlit models.
Power Source:
5
= +5V
9
= +9V
Panel cutout punch
DMS-20 bezel assembly
DMS-20 bezel assembly with sealing gasket
Application/evaluation board with standard
MOLEX connector, decimal point solder pads
and attenuation resistor pads.
A panel-mount retaining clip is supplied with each model.
See
www.murata-ps.com/dpm-availability
for model-specific availability.
Power Supply Requirements (5V Models)
Supply Voltage
Supply Current:
Standard Models
Backlit Models
–
–
+400
+35
+650
+50
µA
mA
+4.75
+5.00
+5.25
Volts
TECHNICAL NOTES
1. REFERENCE OUTPUT (Pin 8) and INPUT (Pin 7):
Pin 8 is a precision
reference actively trimmed at the factory. In normal operation, pin 8
must be tied to pin 7 to achieve all listed accuracy and drift specifica-
tions.
2. ANALOG COMMON (Pin 10):
This pin is connected to an internal,
low-noise, “relative” ground. It is used in certain differential and “float-
ing” measurements as described in the Applications section of this data
sheet and Ap Note DMS-AN3 at
http://www.murata-ps.com/data/meters/dms-an3.pdf.
Pin 10 should
not be connected to pin 3 (5V RETURN/–BATTERY) or to your
system’s analog ground.
3. Decimal Point Placement:
The location of the decimal point is user-
selectable, and the decimal point control pins (DP1-DP3) are active low
functions. Select the appropriate decimal point by tying the appropriate
Power Supply Requirements (9V Models)
Supply Voltage
Supply Current:
Standard Models
Backlit Models
Display
Display Type and Size
Polarity Indication
Overrange Indication
3½ digit, 0.37"/9.4mm high LCD
Autopolarity ("–" for negative Vin)
"–1_ _ _ " for negative Vin
"1_ _ _ " for positive Vin
–
–
+230
+35
+350
+50
µA
mA
+7.5
+9.0
+14.0
Volts
www.murata-ps.com/support
MPM_DMS20LCD.C01
Page 2 of 6
DMS-20LCD Series
3½ Digit, LCD Display Digital Panel Voltmeters
pin (pin 4, 5 or 6) to pin 3 (5V RETURN/–BATTERY). Unused decimal
point location pins should be left open. For 5V-powered models, the
decimal location pins are TTL compatible and may be hard wired as
described above or driven with 5V TTL logic gates.
4. BACKLIGHT (Pin 9) Function:
Grounding pin 9 (i.e. connecting it to
pin 3) turns on the backlighting LED’s. For non-backlit models, pin 9
has no internal connection. All backlit models include internal current-
limiting resistors. With nominal +5V or 9V supplies, backlit devices
typically draw 35mA of supply current. The current drawn by the back-
light (and therefore the current drawn by the meter) can be reduced by
installing a 1/4 Watt resistor between pins 3 and 9. The brightness of
the meter will be reduced proportionately.
9V-powered backlit models function with supply voltages up to +14V,
however, activating the backlight with voltages greater than 9.2V can
damage the meter. Therefore, a 1/4 Watt series resistor must be
installed between pins 3 and 9 in these situations. The value of the
series resistor is determined using the following formula:
+BATTERY – 9.2V
0.035
8. Suggested Mating Connectors:
Panel mounted:
Connector housing
Terminal type
Crimping tool
Wire size
Insulation diameter
Stripping length
Board mounted:
Socket
Murata Power Solutions P/N 4320-01069-0
Murata Power Solutions P/N 4400-01032-0
Murata Power Solutions P/N 39-2099000
22 to 26 AWG
0.062” (1.57mm) maximum
0.100 to 0.125” (2.54 to 3.17mm)
Murata Power Solutions P/N 4320-01074-0
APPLICATIONS
DMS-20LCD meters are available in either 5V-powered or 9V-powered
models. 9V devices operate directly from 7.5V to 14V supplies (usually
batteries) without the need for external voltage regulators. 9V devices,
however, can not be used to measure voltages referenced to the negative
battery terminal (pin 3) because the minus input to the meter (pin 12, (–)
INPUT LO) must always be at least 1.5V above pin 3. 9V-powered meters
can only be used to make differential and not single-ended measurements.
5V-powered devices operate from any well-regulated +5V supply and will
accurately measure voltages both above and below pin 3 (5V RETURN) in
either single-ended or differential configurations.
1. Single-Ended Input Configurations:
True single-ended measure-
ments can only be made with 5V-powered meters. The circuit of Figure
2 avoids problems normally associated with ground-loop currents.
Separate ground runs should be used for 5V RETURN (pin 3) and (–)
INPUT LO (pin 12).
R
Series
=
Ohms
Example: If +BATTERY (pin 1 with respect to pin 3) is +12.6V,
R
Series
=
+12.6 – 9.2V
0.035
Ohms
R
Series
= 97 Ohms
5. Low Battery Annunciator:
The “B” annunciator in the upper left-hand
corner of the display turns on when the supply voltage for 5V-powered
models falls below approximately +3.7V, or when the supply voltage for
9V-powered models falls below approximately 7.2V. However, the low-
battery annunciator’s turn-on threshold can vary significantly from unit-
to-unit: as low as 2.7V for 5V-powered meters, and as low as 5.4V for
9V-powered models. Applications that use the LOW BAT annunciator
must be fully tested by the user, using a combination of low supply volt-
ages and the input signal’s minimum and maximum levels, to ensure
that all display readings are valid as long as the LOW BAT annunciator
remains off.
6. Gain Adjust:
There is a gain-adjust potentiometer on the back of each
meter. It has approximately ±50 counts (±2.5%) range of adjustment.
Since these devices essentially have no zero/offset errors, a gain
adjustment is effectively an overall accuracy adjustment. Though they
may be performed at any point (except zero), accuracy adjustments
are most effective when performed with higher level input signals. The
circuit shown in Figure 9 provides ±10% range of adjustment.
7. Soldering Methods:
All models in the DMS-20LCD Series easily
withstand most common wave soldering operations. We recom-
mend, however, that you evaluate the effects your particular soldering
techniques may have on the meter’s plastic case and high-precision
electrical performance. We recommend the use of no-clean solders.
+
V
IN
–
11
(+) IN HI
DMS-20LCD-1-5
8
REF OUT
12
(–) IN LO
1
+5V SUP
6
DP1
3
7
REF IN
5V RET
120 VAC
AC to DC Converter
Figure 2. Single-Ended Input Configuration
(5V-Powered Models)
www.murata-ps.com/support
MPM_DMS20LCD.C01
Page 3 of 6
DMS-20LCD Series
3½ Digit, LCD Display Digital Panel Voltmeters
APPLICATIONS
2. Differential Input Configurations:
Differential measurements can be
made with either 5V-powered or 9V-powered meters. Figure 3, though
not a practical real-world application, uses a voltage divider to demon-
strate the concept of a differential input signal. Be careful not to exceed
the ±2V common mode voltage limitation for 5V powered meters.
4. Floating Signal Source Measurements:
Floating signals can be
measured using the circuits shown in Figures 5 and 6. Figure 5 uses
a 5V-powered meter. Figure 6 uses a 9V-powered meter. Connecting
pin 10 (ANALOG COMMON) to (–) INPUT LO (pin 12) provides the
reference point for the meter’s input.
A “floating” input is a signal that has no galvanic connection to the
meter’s power supply. In the figures below, the 1.5V battery illustrates a
true floating input.
DMS-20LCD-1-5
8
REF OUT
DMS-20LCD-1-5
REF OUT
8
11
(+) IN HI
R1
1k
REF IN
7
DP1
6
12
(–) IN LO
R2
1k
11
(+) IN HI
1
+5V SUP
3
5V RET
R3
1k
1.5V
CELL
+
–
12
(–) IN LO
7
REF IN
1
3
5V RET
6
DP1
120 VAC
+5V SUP
AC to DC Converter
Figure 3. Differential Input Configuration
(5V-Powered Models)
120 VAC
AC to DC Converter
3. Engineering Scaling:
For measuring voltages greater than the full
scale input range of a given meter, the input signal must be attenuated.
A simple voltage divider (similar to that shown in Figure 4) will scale
the input to within the range of the selected meter. R1 and R2 should
be precision, ±1%, metal-film resistors with absolute TCR’s less than
50ppm/°C. See Ap Note 4 for more information on engineering scaling.
50k < R1 + R2 < 10M
R2
R1 + R2
x V
IN
= Reading
1.5V
CELL
+
Figure 5. Floating Input Measurements
(5V-Powered Models)
11
(+) IN HI
10
ANA COMM
12
(–) IN LO
1
+ BAT
DMS-20LCD-1-9
8
REF OUT
–
7
REF IN
3
–BAT
+
6
DP1
120 VAC
www.murata-ps.com/support
MPM_DMS20LCD.C01
Page 4 of 6
+
R1
V
IN
R2
11
(+) IN HI
9V
BATTERY
DMS-20LCD-1-5
8
REF OUT
–
Figure 6. Floating Input Measurements
(9V-Powered Models)
12
(–) IN LO
7
REF IN
1
+5V SUP
3
5V RET
–
AC to DC Converter
Figure 4. Input Attenuation Circuit
5. Process Control (4-to-20mA) Measurements:
In many common
process-control applications, a 4-to-20mA current loop is used to
transmit information. Because DMS-20LCD meters have such high
input impedance, a simple shunt resistor across the meter’s input can
be used to convert the loop current to a voltage. See Figure 7. The
value of the shunt resistor is a function of the scaling requirements of
the particular application and can be calculated using the following
equation:
DMS-20LCD Series
3½ Digit, LCD Display Digital Panel Voltmeters
APPLICATIONS
R
Shunt
= R1 = V
Fsr
/ I
Fsr
Where:
V
Fsr
= Full scale reading (in Volts)
I
Fsr
= Relative full scale current (in Amps)
Example: For a meter with a 2V full scale input (1.999 full
scale reading) and a desired full scale display reading of
1000 (with an input of 20mA), V
Fsr
= 1.000 Volts
R
Shunt
= 1.000V/(0.020 – 0.004)A
R
Shunt
= 1.000V/0.016A = 62.5 Ohms
REF OUT
8
Therefore, the 9V battery voltage appears to the meter inputs as 0.9V.
With the decimal point moved to its DP2 position
(pin 5 tied to pin 3), the meter reads 9.00 Volts.
The circuit can be calibrated by first measuring the actual battery volt-
age with another meter and then adjusting the gain-adjust potentiom-
eter on the back of the DMS-20LCD until a similar reading is obtained.
If possible, the resistors in the divider should be ±1% metal-film types
with TCR’s less than 50ppm/°C.
DMS-20LCD-1-9
11
(+) IN HI
R1
45.3k
To calibrate the circuit of Figure 7, perform the following:
1. With 4mA applied, adjust the 50k potentiometer (R2) to
display a reading of "000" (assuming that is the desired
reading).
2. With 20mA applied, adjust the gain-adjust potentiometer on
the back of the meter to display a reading of "1999". For different full
scale readings, alter the value of R
Shunt
accordingly.
REF IN
7
1
+BAT
9V
BATTERY
–
+
12
(–) IN LO
R2
10.1k
3
–BAT
5
DP2
R3
45.3k
Figure 8. Power Supply Monitor
(9V-Powered Models)
11
(+) IN HI
10
ANA COMM
12
(–) IN LO
1
R2
+5V SUP
3
5V RET
7
REF IN
DMS-20LCD-1-5
8
REF OUT
4-20mA
6. Power Supply Monitoring:
A popular application for Murata Power
Solutions’ low-power LCD meters is monitoring the supply voltage in
battery-operated portable equipment. Figure 8 demonstrates how a
9V-powered DMS-20LCD can be used to monitor its own supply. The
meter used is the DMS-20LCD-1-9. A three-resistor voltage divider is
used to attenuate the battery voltage and also to satisfy the require-
ment that the input voltages applied to pins 12 and 11 be at least 1.5
Volts above and below the battery voltage applied to pins 1 (+BAT-
TERY) and 3 (–BATTERY). The divider should be designed so that
1/10th the battery voltage falls across the inputs to the meter:
R2
= 0.1
(R1 + R2 + R3)
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MPM_DMS20LCD.C01
Page 5 of 6
+
R1
7. External Gain Adjustment:
Connect REFERENCE OUT
(pin 8) to REFERENCE IN (pin 7) for normal, factory calibrated,
operation. Use the circuit shown in Figure 9 for applications needing
external gain adjustment. Calibration is performed with a precise,
near-full-scale, input voltage.
11
(+) IN HI
–
50k
DMS-20LCD
120 VAC
OUT
VOLTAGE
CALIBRATOR
COM
3
5V RET/
–BAT IN
12
(–) IN LO
10
ANA
COMM
8
NC
8.06k, 1%
7
REF
IN
2k
17.4k, 1%
1
+5V IN/
+BAT IN
Connections
for ±2V, ±20V
and ±200V models
AC to DC Converter
12
Figure 7. 4-to-20mA Current Loop Operation
(5V-Powered Models)
For +5V models, tie (–) IN LO to pin 3.
For +9V models, tie (–) IN LO to pin 10
732, 1%
200
= 10 to 20 Turns
24.3k, 1%
Connections
for ±200mV
models
Figure 9. External Gain Adjustment
Analog electronics
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