DMS-20PC データシートの表示（PDF） - DATEL Data Acquisition products
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DMS-20PC
DATEL Data Acquisition products
DMS-20PC Datasheet PDF : 6 Pages
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DMS-20PC
3½ D I G I T, L E D D I S P L AY D I G I TA L PA N E L V O LT M E T E R S
Applications
2. Differential Input Configurations: Differential measurements
can be made with all DMS-20PC 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.
REF OUT 8
DMS-20PC-1
R1
11
1k
(+) IN HI
REF IN 7
DP1 6
R2
12
1k
(–) IN LO
1
2
3
R3
1k
+5V SUP
DISPLAY 5V RET
ENABLE
120 VAC
DATEL
UPA-5/500
AC to DC Converter
Figure 3. Differential Input Configuration
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.
50kΩ < R1 + R2 < 10MΩ
R2 x VIN = Reading
R1 + R2
R1
VIN
11
(+) IN HI
DMS-20PC-1
8
REF OUT
R2
12
(–) IN LO
–
1
+5V SUP
2
DISPLAY
ENABLE
7
REF IN
3
5V RET
120 VAC
DATEL
UPA-5/500
AC to DC Converter
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 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.
+
1.5V
CELL
–
11
(+) IN HI
12
(–) IN LO
1
+5V SUP
120 VAC
DATEL
UPA-5/500
AC to DC Converter
DMS-20PC-1
8
REF OUT
2
DISPLAY
ENABLE
3
5V
RET
7
REF IN
6
DP1
Figure 5. Floating Input Measurements
+
1.5V
CELL
–
11
(+) IN HI
10
ANA COMM
12
(–) IN LO
1
+5V SUP
120 VAC
DATEL
UPA-5/500
DMS-20PC-1
8
REF OUT
2
DISPLAY
ENABLE
3
5V
RET
7
REF IN
6
DP1
AC to DC Converter
Figure 6. Floating Input Measurements
(Alternate Configuration)
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-20PC 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:
RShunt = R1 = VFsr / I Fsr
Where: VFsr = Full scale reading (in Volts)
IFsr = Relative full scale current (in Amps)
4
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