DMS-20LCD Series

3½ Digit, LCD Display Digital Panel Voltmeters

www.murata-ps.com

MPM_DMS20lcd.B03 Page 5 of 6

APPLICATIONS

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

Where:

Example: For a meter with a 2V full scale input (1.999 full

scale reading) and a desired full scale display reading of

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-oper-

ated 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 bat-

tery 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 volt-

age with another meter and then adjusting the gain-adjust potentiom-

eter 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)

13

+5V SUP

5V RET

DATEL

UPA-5/500

120 VAC

AC to DC Converter

12

(–) IN LO

10

ANA COMM

11

(+) IN HI

R1

–

4-20mA

50k

R2

8

7

REF OUT

REF IN

DMS-20LCD-1-5

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