DMS-20LCD データシートの表示（PDF） - DATEL Data Acquisition products
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DMS-20LCD
DATEL Data Acquisition products
DMS-20LCD Datasheet PDF : 6 Pages
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DMS-20LCD
3½ D I G I T, L C 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 either 5V-powered or 9V-powered 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.
D M S -2 0 L C D -1 -5
11
R1
1k
REF O UT 8
(+ ) IN H I
R E F IN
7
DP1 6
1
+5V S U P
R2
12
1k
( ) IN L O
R3
3
1k
5V R E T
8 5 -2 6 4 V a c
D A TEL
D M S -P S 1 -C M
A C to D C C o n v e rte r
Figure 3. Differential Input Configuration
(5V-Powered Models)
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.
50kΩ < R1 + R2 < 10MΩ
R2 x VIN = Reading
R1 + R2
R1
V IN
R2
11
(+ ) IN H I
D M S -2 0 L C D -1 -5
8
REF O UT
12
( ) IN L O
1
+5V S U P
3
5V R E T
7
R E F IN
8 5 -2 6 4 V a c
D A TEL
D M S -P S 1 -C M
A C to D C C o n v e rte r
Figure 4. Input Attenuation Circuit
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.
1 .5 V
C E LL
11
(+ ) IN H I
D M S -2 0 L C D -1 -5
8
REF O UT
12
( ) IN L O
1
+5V S U P
3
5V R E T
7
R E F IN
6
DP1
8 5 -2 6 4 V a c
D A TEL
D M S -P S 1 -C M
A C to D C C o n v e rte r
Figure 5. Floating Input Measurements
(5V-Powered Models)
1 .5 V
C E LL
11
(+ ) IN H I
10
ANA CO M M
D M S -2 0 L C D -1 -9
8
REF O UT
12
( ) IN L O
1
+ BAT
7
R E F IN
3
6
B A T
DP1
9V
BATTER Y
Figure 6. Floating Input Measurements
(9V-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
4
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