DMS-30PC Series
APPLICATIONS
Example: For a meter with a 2V full scale input (1.999 full
scale reading) and a desired 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
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 "1000". For
different full scale readings, alter the value of R
Shunt
accordingly.
11
(+) IN HI
10
ANA COMM
12
(–) IN LO
9
1.23V
REF
1
5V SUP
3
5V RET
3�½ Digit, LED Display Low-Power,
Miniature Digital Panel Voltmeters
and thermal run-away. When using other, higher-power, DMS-30PC
models with three-terminal regulators, be sure to consult the regula-
tor manufacturer's data sheet to ensure the regulator is being utilized
safely and correctly.
7. Digital Ammeter:
Digital ammeters are finding ever-increasing
usage because analog-style ammeters (moving-vane types) now cost
roughly the same as their digital counterparts. Additionally, analog
ammeters are not nearly as rugged as modern digital panel voltme-
ters. Figure 9 illustrates a typical ammeter application. The circuit
uses a ±200mV input meter
— the preferred range for most ammeters — to measure the voltage
developed across a 0.1Ω current shunt. The circuit shown represents
a basic ammeter connection diagram. A detailed application note
describing digital dc ammeters is included in DATEL's new Digital
Panel Meter Databook.
1
+5V SUP
DMS-30PC-1
8
REF OUT
DMS-30PC-0
8
REF OUT
4-20mA
85-264Vac
6. Power Supply Monitoring:
One of the most common digital panel
meter applications involves monitoring the output voltage of the
system power supply — often this supply also powers the meter
itself. The low-power, red LED DMS-30PC-2-RL can be configured
to allow power supply monitoring over the range of 4.5-18Vdc. The
circuit in Figure 8 uses a low-drop-out, three-terminal regulator (LM-
2931Z-5, available from National Semiconductor) to provide regulated
5V power to the meter. The LM-2931 was chosen because it has the
following on-chip protection features: reverse polarity, short circuit
+
R1
+
5Vdc
7
REF IN
–
3
5V RET
6
DP1
7
REF IN
12
(–) IN LO
0.150V
1.5 Amp (Load Current)
11
(+) IN HI
R2
–
50k
DATEL
DMS-PS1-CM
0.1W
R
Shunt
Load
(3.3 W)
AC to DC Converter
Figure 7.
4-to-20mA Current Loop Operation
Figure 9.
Basic DC Ammeter Circuit
8. External Gain Adjustment:
Connect REFERENCE OUT
(pin 8) to REFERENCE IN (pin 7) for normal, factory calibrated,
operation. Use the +1.23V REFERENCE OUT (pin 9) for applica-
tions needing external gain adjustment. Figure 10 shows the wiring
configuration for each model. Calibration is performed with a precise,
near-full-scale, input voltage.
11
(+) IN HI
DMS-30PC
OUT
VOLTAGE
CALIBRATOR
COM
3
5V RET
12
(–) IN LO
10
ANA COMM
8
NC
8.45k, 1%
1k
10 to 20 Turns
7
REF IN
9
1.23V REF
LM2931Z-5
IN
OUT
GND
4.5 - 18Vdc
22μF
10V
(+) IN HI
11
1
+5V SUP
DMS-30PC-2-RL
+
–
+
3
5V RET
5
DP2
7
REF
IN
8
REF
OUT
12
(–) IN LO
Connections
for ±2V, ±20V
and ±200V models
1k
10 to 20 Turns
8.45k, 1%
Connections
for ±200mV
models
Figure 10.
External Gain Adjustment
Figure 8.
4.5-18V Power Supply Monitor
www.murata-ps.com
Technical enquiries
email: sales@murata-ps.com, tel:
+1 508 339 3000
MPM_DMS_30PC.F03
Page 5 of 6
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