DATEL, Inc., Mansfield, MA 02048 (USA)
Tel: (508)339-3000, (800)233-2765 Fax: (508)339-6356
Email: sales@datel.com
Internet: www.datel.com
Features
Figure 1. DMS-20LCD Series Simplified Schematic
DMS-20LCD Series, 3 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 incorpo-
rate 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 400A) or a
single +9V supply/battery (drawing 230A). 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.
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
Backlit displays optional
Epoxy-encapsulated, 12-pin DIP
Panel or pc-board mountable
4 differential input voltage ranges
High accuracy, 1 count (0.05%)
Single +5V supply or 9V battery
Low-battery annunciator
User-selectable decimal point placement
0 to +60C temperature range
3 Digit, LCD Display
Low-Cost, Subminiature
Digital Panel Voltmeters
DMS-20LCD Series
Actual Size
(+) INPUT HI
() INPUT LO
ANALOG
COMMON
REFERENCE OUT
REFERENCE IN
+5V SUPPLY/
+BATTERY
R1
DP 1
DP 2
DP 3
6
5
4
9
11
12
10
8
7
1
3
DC/DC
CONVERTER
2
5V RETURN/
BATTERY
+5V
5V
R2
+2.0V
DATA
909k
V+
V
A/D
CONVERTER
0 Vdc
0.01F
N.C.
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.
J1
DC/DC converter is not used on 9V-powered models,
J1 is connected.
N.C./BACKLIGHT
Used on backlit models only.
N.C. for non-backlit models.
+5V
Only used on 200mV (-0) and 2V (-1) models.
1
2
3
1
2
4
3
4
www.datel.com
2
DMS-20LCD
3 D I G I T , L C D D I S P L A Y D I G I T A L P A N E L V O L T M E T E R S
Performance/Functional Specifications
Typical at T
A
= +25C and supply voltage = +5V (using the single-ended input circuit) or +9V
(using the differential input circuit), unless otherwise noted.
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.
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).
See Technical Notes.
Leave blank for standard
models.
Add
B
for backlit models.
DMS-20LCD - 1 - 5
Accessories:
DMS-20-CP
Panel cutout punch
DMS-BZL3
DMS-20 bezel assembly
DMS-BZL4
DMS-20 bezel assembly with sealing gasket
DMS-EB2
Application/evaluation board with standard
MOLEX connector, decimal point solder
pads and attenuation resistor pads.
DMS-PS1-CM
+5V/1.0A AC/DC power supply module
Input Range:
0
= 200mV
1
= 2V
2
= 20V
3
= 200V
Power Source:
5
= +5V
9
= +9V
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 specifications.
2. ANALOG COMMON (Pin 10):
This pin is connected to an
internal, low-noise, "relative" ground. It is used in certain
differential and "floating" measurements as described in the
Applications section of this data sheet and Ap Note 3 of the DATEL
Panel Meter Catalog.
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 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.
Ordering Information
A panel-mount retaining clip is supplied with each model.
Analog Inputs
Min.
Typ.
Max.
Units
Full Scale Input Range:
DMS-20LCD-0
--
200
--
mV
DMS-20LCD-1
--
2
--
Volts
DMS-20LCD-2
--
20
--
Volts
DMS-20LCD-3
--
200
--
Volts
Input Impedance:
DMS-20LCD-0, -1
100
1000
--
M
DMS-20LCD-2, -3
0.8
1
--
M
Overvoltage Protection:
DMS-20LCD-0, -1, -2
--
--
100
Volts
DMS-20LCD-3
--
--
250
Volts
Common Mode Voltage Range
--
--
2
Volts
CMRR
(dc to 60Hz)
--
86
--
dB
Control Inputs
Decimal Point Placement
(Pins 4-6):
Functionality
Tie to pin 3 to activate
Logic Compatibility
TTL (on 5V-powered models)
Backlight
(Pin 9)
Tie to pin 3 to turn on backlight
Performance
Sampling Rate
2.5 samples per second
Accuracy
(1 minute warm-up):
DMS-20LCD-0 (V
IN
= +0.19V)
--
1
2
Counts
DMS-20LCD-1 (V
IN
= +1.9V)
--
1
2
Counts
DMS-20LCD-2 (V
IN
= +19V)
--
2
3
Counts
DMS-20LCD-3 (V
IN
= +190V)
--
2
3
Counts
Zero Reading
(V
IN
= 0 Volts)
" 001"
"000"
"001"
Temperature Drift
(0 to +60C)
--
0.2
0.4
Cnts/C
Power Supply Requirements (5V Models)
Supply Voltage
+4.75
+5.00
+5.25
Volts
Supply Current:
Standard Models
--
+400
+600
A
Backlit Models
--
+35
+50
mA
Power Supply Requirements (9V Models)
Supply Voltage
+7.5
+9.0
+14.0
Volts
Supply Current:
Standard Models
--
+230
+350
A
Backlit Models
--
+35
+50
mA
Display
Display Type and Size
3 Digit LCD, 0.37"/9.4mm high
Polarity Indication
Autopolarity ("" for negative V
IN
)
Overrange Indication
"1_ _ _ " for negative V
IN
"1_ _ _ " for positive V
IN
Physical/Environmental
Operating Temperature
0
--
+60
C
Storage Temperature
20
--
+75
C
Humidity
(Non-condensing)
0
--
95
%
Case Material
Polycarbonate
Weight
0.4 ounces (11 grams)
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3
3 D I G I T , L C D D I S P L A Y D I G I T A L P A N E L V O L T M E T E R S
DMS-20LCD
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
measurements 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).
8. Suggested Mating Connectors:
Panel mounted:
Connector housing
DATEL P/N 39-2079400
Terminal type
DATEL P/N 39-2099090
Crimping tool
DATEL P/N 39-2099000
Wire size
22 to 26 AWG
Insulation diameter
0.062" (1.57mm) maximum
Stripping length
0.100 to 0.125" (2.54 to 3.17mm)
Board mounted:
Socket
DATEL P/N 39-2359625
Applications
Figure 2. Single-Ended Input Configuration
(5V-Powered Models)
R
Series
= Ohms
+12.6 9.2V
0.035
Example: If +BATTERY (pin 1 with respect to pin 3) is +12.6V,
+BATTERY 9.2V
0.035
R
Series
= 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 +3.75V or
when the supply voltage for 9V-powered models falls below
approximately 7.2V. This function can not be disabled.
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
recommend, 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 water-soluble solders and thorough cleaning
procedures.
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 backlight (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:
1
1 2
3
+ 5 V S U P
( ) I N L O
5 V R E T
D A T E L
D M S - P S 1 - C M
8 5 - 2 6 4 V a c
1 1
( + ) I N H I
6
D P 1
+
A C t o D C C o n v e r t e r
V
I N
D M S - 2 0 L C D - 1 - 5
7
R E F O U T
R E F I N
8
4
DMS-20LCD
3 D I G I T , L C D D I S P L A Y D I G I T A L P A N E L V O L T M E T E R S
R2
R1 + R2
x V
IN
= Reading
50k
< R1 + R2 < 10M
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.
Figure 3. Differential Input Configuration
(5V-Powered Models)
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
Figure 6. Floating Input Measurements
(9V-Powered Models)
Figure 5. Floating Input Measurements
(5V-Powered Models)
Figure 4. Input Attenuation Circuit
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 demonstrate the concept of a differential input
signal. Be careful not to exceed the 2V common mode voltage
limitation for 5V powered meters.
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.
1
1 2
3
+ 5 V S U P
( ) I N L O
5 V R E T
1 1
( + ) I N H I
6
A C t o D C C o n v e r t e r
R 2
R 1
R 3
1 k
1 k
1 k
8
7
R E F I N
D P 1
R E F O U T
D M S - 2 0 L C D - 1 - 5
D A T E L
D M S - P S 1 - C M
8 5 - 2 6 4 V a c
R 2
1 1
1 2
( + ) I N H I
( ) I N L O
V
I N
R 1
+
1
3
+ 5 V S U P
5 V R E T
A C t o D C C o n v e r t e r
8
7
R E F O U T
R E F I N
D M S - 2 0 L C D - 1 - 5
D A T E L
D M S - P S 1 - C M
8 5 - 2 6 4 V a c
1
3
+ 5 V S U P
5 V R E T
6
D P 1
A C t o D C C o n v e r t e r
1 2
( ) I N L O
1 1
( + ) I N H I
1 . 5 V
C E L L
+
8
7
R E F O U T
R E F I N
D M S - 2 0 L C D - 1 - 5
D A T E L
D M S - P S 1 - C M
8 5 - 2 6 4 V a c
1
3
+ B A T
B A T
9 V
B A T T E R Y
6
D P 1
1 2
( ) I N L O
1 0
A N A C O M M
1 1
( + ) I N H I
1 . 5 V
C E L L
+
+
8
7
R E F O U T
R E F I N
D M S - 2 0 L C D - 1 - 9
5
3 D I G I T , L C D D I S P L A Y D I G I T A L P A N E L V O L T M E T E R S
DMS-20LCD
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.
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
function of the scaling requirements of the particular application and
can be calculated using the following equation:
Figure 7. 4-to-20mA Current Loop Operation
(5V-Powered Models)
R2
(R1 + R2 + R3)
= 0.1
6. Power Supply Monitoring:
A popular application for DATEL's
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 requirement 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 (+BATTERY) and 3 (BATTERY). The divider should be
designed so that 1/10th the battery voltage falls across the inputs
to the meter:
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 voltage with another meter and then adjusting the gain-
adjust potentiometer 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.
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.
Figure 9. External Gain Adjustment
Figure 8. Power Supply Monitor
(9V-Powered Models)
Applications
1
3
+ 5 V S U P
5 V R E T
A C t o D C C o n v e r t e r
1 2
( ) I N L O
1 0
A N A C O M M
1 1
( + ) I N H I
R 1
+
4 - 2 0 m A
5 0 k
R 2
8
7
R E F O U T
R E F I N
D M S - 2 0 L C D - 1 - 5
D A T E L
D M S - P S 1 - C M
8 5 - 2 6 4 V a c
1
12
3
+BAT
() IN LO
BAT
11
(+) IN HI
5
DP2
DMS-20LCD-1-9
R2
R1
R3
45.3k
10.1k
45.3k
9V
BATTERY
+
8
7
REF OUT
REF IN
12
VOLTAGE
CALIBRATOR
OUT
10
(+) IN HI
() IN LO
ANA
COMM
= 10 to 20 Turns
7
REF
IN
11
732, 1%
8.06k, 1%
5V RET/
BAT IN
Connections
for 2V, 20V
and 200V models
Connections
for 200mV
models
COM
1
+5V IN/
+BAT IN
17.4k, 1%
2k
24.3k, 1%
3
12
DMS-20LCD
For +5V models, tie () IN LO to pin 3.
For +9V models, tie () IN LO to pin 10
8
NC
200
Q
Q
Q
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