DMS-20PC データシートの表示（PDF） - DATEL Data Acquisition products
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DMS-20PC
DATEL Data Acquisition products
DMS-20PC Datasheet PDF : 6 Pages
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3½ D I G I T, L E 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-20PC
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), VFsr = 1.000 Volts
RShunt = 1.000V/(0.020 – 0.004)A
RShunt = 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 RShunt accordingly.
4-20mA R1
–
11
(+) IN HI
10
ANA COMM
DMS-20PC-1
8
REF OUT
12
(–) IN LO
1
R2
+5V SUP
50k
7
REF IN
2
DISPLAY
ENABLE
3
5V RET
120 VAC
DATEL
UPA-5/500
AC to DC Converter
Figure 7. 4-to-20mA Current Loop Operation
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-20PC-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.
LM2931Z-5
IN OUT
+
GND
+
4.5 - 18Vdc
22µF
–
10V
DMS-20PC-2-RL
1
+5V SUP
2
DISP_EN
3
5V RET
11 (+) IN HI
5
DP2
7
REF
IN
8
REF
OUT
12
(–) IN LO
Figure 8. 4.5V -18V Power Supply Monitor
The LM-2931 was chosen because it has the following on-chip
protection features: reverse polarity, short circuit and thermal
runaway. When using other, higher-power, DMS-20PC models
with three-terminal regulators, be sure to consult the regulator
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 voltmeters. 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
2
+
DISP EN
5VDC
–
3
5V RET
DMS-20PC-0
8
REF OUT
7
6
DP1
12
REF IN
11
(–) IN LO
(+) IN HI
1.5 Amp (Load Current)
0.150V
0.1W
RShunt
Load
(3.3W )
Figure 9. DC Ammeter Circuit
8. External Gain Adjustment: Connect REFERENCE OUT
(pin 8) to REFERENCE IN (pin 7) for normal, factory calibrated,
operation. Use the circuit shown in Figure 10 for applications
needing external gain adjustment. Calibration is performed with
a precise, near-full-scale, input voltage.
OUT
12
VOLTAGE
CALIBRATOR
COM
11
(+) IN HI
3
5V RET
DMS-20PC-1
1
+5V IN
12
(–) IN LO
10
8
7
ANA
NC REF
COMM
IN
8.06k, 1%
Connections
for ±2V, ±20V
and ±200V models
2k 1 17.4k, 1%
732, 1%
200 1
24.3k, 1%
Connections
for ±200mV
models
1 = 10 to 20 Turns
Figure 10. External Gain Adjustment
5
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