DMS-30LCD Series

3½ Digit, LCD Display Digital Panel Voltmeters

www.murata-ps.com

MPM_DMS30LCD.D01 Page 5 of 6

APPLICATIONS

R2

(R1 + R2 + R3)

= 0.1

Figure 7. 4-to-20mA Current Loop Operation

(5V-Powered Models)

Figure 9. External Gain Adjustment

Figure 8. Power Supply Monitor

(9V-Powered Models)

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-30LCD can be used to monitor its own supply. The meter used

is the DMS-30LCD-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:

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

7. External Gain Adjustment: Connect REFERENCE OUT

(pin 8) to REFERENCE IN (pin 7) for normal, factory calibrated, opera-

tion. Use the +1.23V REFERENCE OUT (pin 9) for applications need-

ing external gain adjustment. Figure 9 shows the wiring configuration

for each model. Calibration is performed with a precise, near-full-scale,

input voltage.

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-30LCD 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.

13

+5V SUP

5V RET

DATEL

UPA-5/500

120 VAC

AC to DC Converter

(–) IN LO

ANA COMM

(+) IN HI

R1

–

4-20mA

50k

R2

8

7

REF OUT

REF IN

DMS-30LCD-1-5

1

12

3

+BAT

(–) IN LO

–BAT

11

(+) IN HI

5

DP2

R2

R1

R3

45.3k

10.1k

45.3k

9V

BATTERY

–

8

7

REF OUT

REF IN

DMS-30LCD-1-9

9

(+) IN HI

(–) IN LO

ANA COMM

10

1.23V REF

1k

10 to 20 Turns

8

REF IN

11

1k

10 to 20 Turns

8.45k, 1%

8.45k, 1%

5V RET

7

NC

12

3

For 5V models tie

(–) IN LO to pin 3

For 9V models tie

(–) IN LO to pin 10

12

VOLTAGE

CALIBRATOR

OUT

COM

Connections

for ±2V and

±20V models

Connections

for ±200mV

models

DMS-30LCD