Datasheet DMS-20PC (Murata) - 5

DMS-20PC Series
3½ Digit, LED Display, Low-Cost, Subminiature
APPLICATIONS
Digital Panel Voltmeters
Example:
For a meter with a 2V full scale input (1.999 full scale The LM-2931 was chosen because it has the following on-chip reading) and a desired display reading of "1000" (with an protection features: reverse polarity, short circuit and thermal input of 20mA), VFsr = 1.000 Volts runaway. When using other, higher-power, DMS-20PC models with three-terminal regulators, be sure to consult the regula- RShunt = 1.000V/(0.020 – 0.004)A tor manufacturer's data sheet to ensure the regulator is being RShunt= 1.000V/0.016A = 62.5 Ohms utilized safely and correctly. To calibrate the circuit of Figure 7, perform the following:
7. Digital Ammeter:
Digital ammeters are fi nding ever-increasing 1. With 4mA applied, adjust the 50kΩ potentiometer (R2) to usage because analog-style ammeters (moving-vane types) display a reading of "000" (assuming that is the desired now cost roughly the same as their digital counterparts. Addi- reading). tionally, analog ammeters are not nearly as rugged as modern digital panel voltmeters. Figure 9 illustrates a typical ammeter 2. With 20mA applied, adjust the gain-adjust potentiometer application. The circuit uses a ±200mV input meter — the on the back of the meter to display a reading of "1000". preferred range for most ammeters — to measure the voltage For different full scale readings, alter the value of RShunt developed across a 0.1Ω current shunt. The circuit shown accordingly.
http://www.murata-ps.com/data/meters/dms-an6.pdf
represents a basic ammeter connection diagram. Click
here
to view a detailed application note describing digital dc ammeters.
DMS-20PC-1 11
(+) IN HI
8
+ REF OUT
10
ANA COMM
1 DMS-20PC-0
+5V SUP
12 8
4-20mA R1
7 2
(–) IN LO REF OUT REF IN + DISP EN 5Vdc
1 2 3 3
– +5V SUP DISPLAY 5V RET 5V RET R2 ENABLE –
7
REF IN 50k
6
DP1
12 11
(–) IN LO (+) IN HI 85-264Vac 0.150V 1.5 Amp (Load Current) AC to DC Converter 0.1W Load RShunt (3.3 ) W
Figure 7.
4-to-20mA Current Loop Operation
Figure 9.
Basic DC Ammeter Circuit
6. Power Supply Monitoring:
One of the most common digital panel meter applications involves monitoring the output voltage
8. External Gain Adjustment
: Connect REFERENCE OUT of the system power supply — often this supply also powers the (pin 8) to REFERENCE IN (pin 7) for normal, factory calibrated, meter itself. The low-power, red LED DMS-20PC-2-RL can be operation. Use the circuit shown in Figure 10 for applications confi gured to allow power supply monitoring over the range of needing external gain adjustment. Calibration is performed 4.5-18Vdc. The circuit in Figure 8 uses a low-drop-out, three-ter- with a precise, near-full-scale, input voltage. minal regulator (LM-2931Z-5, available from National Semicon-
11 DMS-20PC-1
ductor) to provide regulated 5V-power to the meter. (+) IN HI OUT
3 1
VOLTAGE 5V RET +5V IN
12 DMS-20PC-2-RL
CALIBRATOR LM2931Z-5
12
COM
1 11
(+) IN HI Connections (–) IN LO for ±2V, ±20V +5V SUP
10 8 7
IN OUT and ±200V models
2
ANA NC REF COMM IN + GND DISP EN + 8.06k, 1% 1 2k 17.4k, 1% 4.5 - 18Vdc 22µF
3
10V – 5V RET
5
Connections DP2 for ±200mV
7 8 12
models 1 REF REF (–) IN LO 732, 1% 24.3k, 1% 200 IN OUT 1 = 10 to 20 Turns
Figure 10.
External Gain Adjustment
Figure 8.
4.5 -18V Power Supply Monitor
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