Datasheet

DMS-20LCD Series
3½ Digit, LCD Display Digital Panel Voltmeters
www.murata-ps.com/dpm
email: [e-mail]
05 Apr 2011 MPM_DMS20LCD.B08 Page 4 of 6
APPLICATIONS
R2
R1 + R2
x VIN = Reading
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 “fl oating” input is a signal that has no galvanic connection to the
meter’s power supply. In the fi gures below, the 1.5V battery illustrates a
true fl oating input.
Figure 3. Differential Input Confi guration
(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 Confi gurations: 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-fi lm resistors with absolute TCR’s less than
50ppm/°C. See Ap Note 4 for more information on engineering scaling.
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-1-9
1
12
3
+5V SUP
(–) IN LO
5V RET
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
V
IN
R1
+
–
1
3
+5V SUP 5V RET
120 VAC
AC to DC Converter
8
7
REF OUT
REF IN
DMS-20LCD-1-5
13
+5V SUP 5V RET
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