National Instruments SCB-68 - Manual (Page 64)

Chapter 5 Adding Components for Special Functions
© National Instruments Corporation 5-19 SCB-68 Shielded Connector Block User Manual
Figure 5-19. Attenuating Voltage with a Voltage Divider
Theory of Operation
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 5-12 to determine the V
m
that the DAQ device measures:
(5-12)
Use Equation 5-13 to determine the overall gain of a voltage divider circuit:
(5-13)
The accuracy of Equation 5-13 depends on the tolerances of the resistors
that you use.
Caution The SCB-68 is not designed for any input voltages greater than 42 V, even if a
user-installed voltage divider reduces the voltage to within the input range of the DAQ
device. Input voltages greater than 42 V can damage the SCB-68, any devices connected
to it, and the host computer. Overvoltage can also cause an electric shock hazard for the
operator. NI is not responsible for damage or injury resulting from such misuse.
R2 V
in
V
m
+
–
+
–
R1
V
m
V
in
R
2
R
1
R
2
+
------------------
 
 
=
G
V
m
V
in
-------
R
2
R
1
R
2
+
------------------ = =