DMS-20LCD Series

3½ Digit, LCD Display Digital Panel Voltmeters

www.murata-ps.com

MPM_DMS20lcd.B03 Page 4 of 6

APPLICATIONS

R2

R1 + R2

50k

< R1 + R2 < 10M

4. Floating Signal Source Measurements: Floating signals can be

measured using the circuits shown in Figures 5 and 6. Figure 5 uses

a 5V-powered meter. Figure 6 uses a 9V-powered meter. Connecting

pin 10 (ANALOG COMMON) to (–) INPUT LO (pin 12) provides the

reference point for the meter’s input.

A “floating” input is a signal that has no galvanic connection to the

meter’s power supply. In the figures below, the 1.5V battery illustrates a

true floating input.

Figure 3. Differential Input Configuration

(5V-Powered Models)

5. Process Control (4-to-20mA) Measurements: In many common

process-control applications, a 4-to-20mA current loop is used to

transmit information. Because DMS-20LCD meters have such high

input impedance, a simple shunt resistor across the meter’s input can

be used to convert the loop current to a voltage. See Figure 7. The

value of the shunt resistor is a function of the scaling requirements of

the particular application and can be calculated using the following

equation:

Figure 6. Floating Input Measurements

(9V-Powered Models)

Figure 5. Floating Input Measurements

(5V-Powered Models)

Figure 4. Input Attenuation Circuit

2. Differential Input Configurations: Differential measurements can be

made with either 5V-powered or 9V-powered meters. Figure 3, though

not a practical real-world application, uses a voltage divider to demon-

strate the concept of a differential input signal. Be careful not to exceed

the ±2V common mode voltage limitation for 5V powered meters.

3. Engineering Scaling: For measuring voltages greater than the full

scale input range of a given meter, the input signal must be attenuated.

A simple voltage divider (similar to that shown in Figure 4) will scale

the input to within the range of the selected meter. R1 and R2 should

be precision, ±1%, metal-film resistors with absolute TCR’s less than

50ppm/°C. See Ap Note 4 for more information on engineering scaling.

1

12

3

+5V SUP

(–) IN LO

5V RET

DATEL

UPA-5/500

120 VAC

11

(+) IN HI

6

AC to DC Converter

R2

R1

R3

1k

1k

1k

8

7

REF IN

DP1

REF OUT

DMS-20LCD-1-5

R2

11

12

(+) IN HI

(–) IN LO

R1

–

1

3

+5V SUP

5V RET

DATEL

UPA-5/500

120 VAC

AC to DC Converter

8

7

REF OUT

REF IN

DMS-20LCD-1-5

13

+5V SUP

5V RET

DATEL

UPA-5/500

120 VAC

6

DP1

AC to DC Converter

12

(–) IN LO

11

(+) IN HI

1.5V

CELL

–

8

7

REF OUT

REF IN

DMS-20LCD-1-5

1

3

+ BAT

–BAT

9V

BATTERY

6

DP1

12

(–) IN LO

10

ANA COMM

11

(+) IN HI

1.5V

CELL

–

–

8

7

REF OUT

REF IN

DMS-20LCD-1-5

DMS-20LCD-1-9