DMS-30PC ETC-unknow, DMS-30PC Datasheet - Page 4

• Manufacturer Part Number: DMS-30PC
• Description: 3 1/2 Digit Led Display Low Power Miniature Digital Panel Voltmeters
• Manufacturer: ETC-unknow

DMS-30PC
2. Differential Input Configurations: Differential measurements
3. Engineering Scaling: For measuring voltages greater than the
4. Floating Signal Source Measurements: Floating signals can
+
–
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.
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.
120 VAC
be measured using the circuits shown in Figures 5 and 6.
V
120 VAC
IN
REF OUT
REF IN
R1
R2
DP1
AC to DC Converter
AC to DC Converter
8
7
6
UPA-5/500
50k < R1 + R2 < 10M
(–) IN LO
UPA-5/500
(+) IN HI
DATEL
Figure 3. Differential Input Configuration
R1 + R2
DATEL
Figure 4. Input Attenuation Circuit
R2
11
12
+5V SUP
+5V SUP
x V
DMS-30PC-1
IN
1
1
= Reading
DMS-30PC-1
3 ½ D I G I T , L E D D I S P L A Y D I G I T A L P A N E L V O L T M E T E R S
3
5V RET
5V RET
3
11
12
(–) IN LO
(+) IN HI
8
REF OUT
7
REF IN
R1
R2
R3
1k
1k
1k
Applications
4
5. Process Control (4-to-20mA) Measurements: In many
120 VAC
Connecting 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.
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:
CELL
1.5V
CELL
Where:
1.5V
120 VAC
AC to DC Converter
–
–
UPA-5/500
AC to DC Converter
DATEL
R
Shunt
V
UPA-5/500
Figure 6. Floating Input Measurements
I
Figure 5. Floating Input Measurements
DATEL
Fsr
Fsr
ANA COMM
(–) IN LO
(–) IN LO
(+) IN HI
(+) IN HI
= R1 = V
= Full scale reading (in Volts)
= Relative full scale current (in Amps)
(Alternate Configuration)
11
12
12
11
10
12
+5V SUP
+5V SUP
1
Fsr
1
/ I
Fsr
5V RET
5V RET
DMS-30PC-1
DMS-30PC-1
3
3
DP1
6
DP1
6
8
REF OUT
7
REF IN
8
7
REF OUT
REF IN