Chapter 5
Using the SCXI-1125
5-4
ni.com
Making High-Voltage Measurements
Another common use of the SCXI-1125 is to make measurements up to
1000 VDC. Making measurements beyond ± 5 V requires use of the an
attenuator terminal block. The SCXI-1327 and SCXI-1313A terminal
blocks have a selectable attenuator for choosing between no attenuation or
100:1 attenuation, which allows you to use the SCXI-1125 with up to
300 V
rms
when using the SCXI-1327 and up to 150 V
rms
when using the
SCXI-1313A.
The TBX-1316 has a fixed 200:1 attenuation, which allows you to use the
SCXI-1125 with up to 1000 VDC, Measurement Category I.
The SCXI-1327 and SCXI-1313A also include a cold-junction sensor so
you can combine thermocouple measurements with high-voltage
measurements. When making signal connections, or when working with
high-voltage signals, refer to the terminal block installation guide. If you
are using the SCXI-1125 to measure signals with attenuation on the
terminal block, an external bias resistor is
not
needed, because a bias
resistor is already used for achieving the attenuation.
Table 5-1 lists the extended ranges of gain possible with the SCXI-1327
and SCXI-1313A. Table 5-2 lists the extended gain possible with the
TBX-1316.
Table 5-1.
Extended Gain and Range Using the SCXI-1327 or SCXI-1313A
Overall
Gain
Input
Range (V)
SCXI-1125
Gain
SCXI-1327
Attenuation
SCXI-1313A
Attenuation
0.01
± 300
1
100
—
0.02
± 250
2
100
—
0.002
± 150
2
100
100
0.05
± 100
5
100
100
0.1
± 50
10
100
100
0.2
± 25
20
100
100
0.5
± 10
50
100
100
2.5
± 2
250
100
100
