DMS-30PC Series
APPLICATIONS
2. Differential Input Configurations:
Differential measurements can
be made with all DMS-30PC meters. Figure 3, though not a practical
real-world application, uses a voltage divider to demonstrate the
concept of a differential input signal. Be careful not to exceed the ±2V
common mode voltage limitation for 5V-powered meters.
DMS-30PC-1
REF OUT
8
R1
1k
3�½ Digit, LED Display Low-Power,
Miniature Digital Panel Voltmeters
pin 10 (ANALOG COMMON) or pin 3 (5V RETURN) 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.
DMS-30PC-1
8
REF OUT
11
(+) IN HI
11
(+) IN HI
+
REF IN
7
DP1
6
12
(–) IN LO
R2
1k
1.5V
CELL
–
12
(–) IN LO
7
REF IN
1
+5V SUP
3
5V RET
6
DP1
1
+5V SUP
3
5V RET
R3
1k
85-264Vac
DATEL
DMS-PS1-CM
85-264Vac
DATEL
DMS-PS1-CM
AC to DC Converter
AC to DC Converter
Figure 3.
Differential Input Configuration
Figure 5.
Floating Input Measurements
3. Engineering Scaling:
For measuring voltages greater than the full
scale input range of a given meter, the input signal must be attenu-
ated. 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 engineer-
ing scaling.
50k < R1 + R2 < 10M
R2
x V
IN
= Reading
R1 + R2
+
DMS-30PC-1
8
REF OUT
11
(+) IN HI
10
ANA COMM
12
(–) IN LO
1
+5V SUP
+
DMS-30PC-1
8
REF OUT
1.5V
CELL
–
7
REF IN
3
5V RET
6
DP1
85-264Vac
DATEL
DMS-PS1-CM
AC to DC Converter
R1
V
IN
R2
11
(+) IN HI
Figure 6.
Floating Input Measurements
(Alternate Configuration)
–
12
(–) IN LO
7
REF IN
1
+5V SUP
3
5V RET
85-264Vac
DATEL
DMS-PS1-CM
AC to DC Converter
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-30PC 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:
R
Shunt
= R1 = V
Fsr
/ I
Fsr
Where:
V
Fsr
= Full scale reading (in Volts)
I
Fsr
= Relative full scale current (in Amps)
Figure 4.
Input Attenuation Circuit
4. Floating Signal Source Measurements:
Floating signals can be
measured using the circuits shown in Figures 5 and 6. Connecting
www.murata-ps.com
Technical enquiries
email: sales@murata-ps.com, tel:
+1 508 339 3000
MPM_DMS_30PC.F03
Page 4 of 6
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