®
®
www.datel.com
DMS-20LCD Series
3½ Digit, LCD Display
Low-Cost, Subminiature
Digital Panel Voltmeters
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 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 800kΩ.
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.
Actual Size
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
•
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 +60°C temperature range
+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
4
DP 3
DATA
9
N.C./BACKLIGHT
4
DP 2
5
+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
Figure 1. DMS-20LCD Series Simplified Schematic
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
DMS-20LCD
3½ 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
= +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 Impedance:
DMS-20LCD-0, -1
DMS-20LCD-2, -3
Overvoltage Protection:
➀
DMS-20LCD-0, -1, -2
DMS-20LCD-3
Common Mode Voltage Range
➁
CMRR
(dc to 60Hz)
Control Inputs
➂
Decimal Point Placement
(Pins 4-6):
Functionality
Logic Compatibility
Backlight
(Pin 9)
Performance
Sampling Rate
Accuracy
(1 minute warm-up):
DMS-20LCD-0 (V
IN
= +0.19V)
DMS-20LCD-1 (V
IN
= +1.9V)
DMS-20LCD-2 (V
IN
= +19V)
DMS-20LCD-3 (V
IN
= +190V)
Zero Reading
(V
IN
= 0 Volts)
Temperature Drift
(0 to +60°C)
Supply Voltage
Supply Current:
Standard Models
Backlit Models
Supply Voltage
Supply Current:
Standard Models
Backlit Models
Display
Display Type and Size
Polarity Indication
Overrange Indication
Physical/Environmental
Operating Temperature
Storage Temperature
Humidity
(Non-condensing)
Case Material
Weight
0
–20
0
--
--
--
+60
+75
95
°C
°C
%
3½ Digit LCD, 0.37"/9.4mm high
Autopolarity ("–" for negative V
IN
)
"–1_ _ _" for negative V
IN
"1_ _ _" for positive V
IN
--
--
--
--
"–001"
--
+4.75
--
--
+7.5
--
--
2.5 samples per second
±1
±1
±2
±2
"000"
±0.2
+5.00
+400
+35
+9.0
+230
+35
±2
±2
±3
±3
"001"
±0.4
+5.25
+600
+50
+14.0
+350
+50
Cnts/°C
Volts
µA
mA
Volts
µA
mA
Counts
Counts
Counts
Counts
Tie to pin 3 to activate
TTL (on 5V-powered models)
Tie to pin 3 to turn on backlight
Accessories:
DMS-20-CP
DMS-BZL3
DMS-BZL4
DMS-EB2
Min.
--
--
--
--
100
0.8
--
--
--
--
Typ.
±200
±2
±20
±200
1000
1
--
--
--
86
Max.
--
--
--
--
--
--
±100
±250
±2
--
Units
mV
Volts
Volts
Volts
MΩ
MΩ
Volts
Volts
Volts
dB
Input Range:
0
= ±200mV
1
= ±2V
2
= ±20V
3
= ±200V
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.
+5V/1.0A AC/DC power supply module
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
See Technical Notes.
Ordering Information
DMS-20LCD - 1 - 5
DMS-PS1-CM
A panel-mount retaining clip is supplied with each model.
Power Supply Requirements
(5V Models)
Order on-line at www.datel.com
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.
Power Supply Requirements
(9V Models)
Polycarbonate
0.4 ounces (11 grams)
2
3½ D I G I T, L C D D I S P L AY D I G I TA L PA N E L V O LT M E T E R S
DMS-20LCD
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:
R
Series
=
+BATTERY – 9.2V
0.035
Ohms
8. Suggested Mating Connectors:
Panel mounted:
Connector housing
Terminal type
Crimping tool
Wire size
Insulation diameter
Stripping length
Board mounted:
Socket
DATEL P/N 39-2079400
DATEL P/N 39-2099090
DATEL P/N 39-2099000
22 to 26 AWG
0.062" (1.57mm) maximum
0.100 to 0.125" (2.54 to 3.17mm)
DATEL P/N 39-2359625
Applications
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 +3.75V 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.
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).
+
V
IN
1 1
(+ ) IN H I
D M S -2 0 L C D -1 -5
8
R E F O U T
1 2
( ) IN L O
7
1
+ 5 V S U P
6
3
D P 1
5 V R E T
R E F IN
8 5 -2 6 4 V a c
D A T E L
D M S -P S 1 -C M
A C to D C C o n v e rte r
Figure 2. Single-Ended Input Configuration
(5V-Powered Models)
3
DMS-20LCD
3½ 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
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.
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.
D M S -2 0 L C D -1 -5
R E F O U T
8
1 1
(+ ) IN H I
R 1
1 k
R E F IN
7
D P 1
6
1
+ 5 V S U P
3
5 V R E T
1 2
( ) IN
L O
R 2
1 k
1 1
(+ ) IN H I
1 .5 V
C E L L
D M S -2 0 L C D -1 -5
8
R E F O U T
R 3
1 k
+
( ) IN
8 5 -2 6 4 V a c
D A T E L
D M S -P S 1 -C M
1 2
L O
1
+ 5 V S U P
3
5 V R E T
6
D P 1
7
R E F IN
A C
to D C
C o n v e rte r
8 5 -2 6 4 V a c
D A T E L
D M S -P S 1 -C M
Figure 3. Differential Input Configuration
(5V-Powered Models)
A C
to D C
C o n v e rte r
Figure 5. Floating Input Measurements
(5V-Powered Models)
1 .5 V
C E L L
50kΩ < R1 + R2 < 10MΩ
1
+ B A T
R2
R1 + R2
+
x V
IN
= Reading
9 V
B A T T E R Y
R 1
V
IN
1 1
(+ ) IN H I
D M S -2 0 L C D -1 -5
8
R E F O U T
Figure 6. Floating Input Measurements
(9V-Powered Models)
R 2
1 2
( ) IN L O
7
1
+ 5 V S U P
3
5 V R E T
R E F IN
8 5 -2 6 4 V a c
D A T E L
D M S -P S 1 -C M
A C to D C C o n v e rte r
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 4. Input Attenuation Circuit
4
+
+
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
(+ ) IN H I
1 0
A N A C O M M
1 2
( ) IN L O
D M S -2 0 L C D -1 -9
8
R E F O U T
7
3
B A T
6
D P 1
R E F IN
3½ 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
Applications
function of the scaling requirements of the particular application and
can be calculated using the following equation:
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
R2
= 0.1
(R1 + R2 + R3)
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.
DMS-20LCD-1-9
To calibrate the circuit of Figure 7, perform the following:
1. With 4mA applied, adjust the 50kΩ 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 OUT
8
11
(+) IN HI
R1
45.3k
12
(–) IN LO
REF IN
7
1
+BAT
9V
BATTERY
–
3
–BAT
5
DP2
R2
10.1k
R3
45.3k
1 1
(+ ) IN H I
D M S -2 0 L C D -1 -5
8
1 0
A N A C O M M
1 2
( ) IN L O
1
3
5 V R E T
7
R E F O U T
Figure 8. Power Supply Monitor
(9V-Powered Models)
4 -2 0 m A
R 1
R E F IN
+ 5 V S U P
R 2
5 0 k
D A T E L
D M S -P S 1 -C M
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.
8 5 -2 6 4 V a c
A C to D C C o n v e rte r
11
(+) IN HI
+
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:
+
DMS-20LCD
OUT
VOLTAGE
CALIBRATOR
COM
3
5V RET/
–BAT IN
12
(–) IN LO
10
ANA
COMM
8
NC
8.06k, 1%
7
REF
IN
2k
Q
17.4k, 1%
1
+5V IN/
+BAT IN
Connections
for ±2V, ±20V
and ±200V models
Figure 7. 4-to-20mA Current Loop Operation
(5V-Powered Models)
12
For +5V models, tie (–) IN LO to pin 3.
For +9V models, tie (–) IN LO to pin 10
732, 1%
200
Q
24.3k, 1%
Connections
for ±200mV
models
Q
= 10 to 20 Turns
Figure 9. External Gain Adjustment
5
Embedded System
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