National Instruments NI SCB-68A, Руководство пользователя

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© National Instruments | 2-35
NI SCB-68A User Manual
Figure 2-34. Measuring Current with Single-Ended Analog Input (AI <i>)
Attenuating Voltage
Transducers can generate more than 10 VDC per channel, but DAQ devices cannot read more
than 10 VDC per input channel. Therefore, you must attenuate output signals from the
transducer to fit within the DAQ device specifications. Figure 2-35 shows how to use a voltage
divider to attenuate the output signal of the transducer.
Figure 2-35. Attenuating Voltage with a Voltage Divider
The voltage divider splits the input voltage ( V
in
) between two resistors ( R
1
and R
2
), causing the
voltage on each resistor to be noticeably lower than V
in
. Use Equation 2-6 to determine the V
m
that the DAQ device measures:
(2-6)
Use Equation 2-7 to determine the overall gain of a voltage divider circuit:
AI i
AI i + 8
y
S C x
E
A
F
G
B
C
D
+
+
+
+ 5 V
AI GND
+ 5 V
AI GND
AI
i
AI
i
+
8
R2 V
in
V
m
+
–
+
–
R1
V
m
V
in
R
2
R
1
R
2
+
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 
=