SCC-LP Series Lowpass Filter Modules User Guide 16 ni.com
Calibrating Gain Errors
The SCC-LPXX is calibrated at the factory before shipment. If you want to
calibrate the SCC-LPXX in your system, you need a voltage source capable
of providing a DC voltage up to ±10 V that is several times more accurate
than the SCC itself.
To calibrate the SCC-LPXX, complete the following steps for each channel
of the module:
1. Select the desired SCC-LPXX channel (X or X+8) on the E Series DAQ
device.
2. Set the gain on the E Series DAQ device so that the ESeries input
range is ±5V.
3. Connect the voltage source to the screw terminals of the desired
channel on the SCC-LPXX.
4. Input 9 VDC to the SCC-LPXX.
5. Using your software, have the ESeries DAQ device read the desired
channel on the SCC-LPXX. Record the value.
6. Input 0 VDC to the SCC-LPXX.
7. Have the ESeries DAQ device read the channel again and record the
new value.
8. Calculate the difference between the two values you recorded
(first reading – second reading).
9. Adjust the appropriate trimpot (X or X+8) on the top of the SCC-LPXX.
Repeat steps 4 through 8 until the difference you get in step 8
equals 9 V.
For example, you connect 9 VDC to the input of CH (X) and the ESeries
DAQ device reads 9.05 V at the SCC output; then you connect 0 VDC to
the input of CH (X) and the E Series DAQ device reads –0.01V at the SCC
output. Subtract the second value from the first (9.05 – (–0.01)) to get a
difference of 9.06V. Because the difference is not equal to 9 V, you adjust
the trimpot until the difference in outputs equals 9V.
Note In this example there may be an offset voltage such that the final voltages are 9.01V
and 0.01 V for a difference of 9 V. The SCC-LPXX trimpot adjusted in step 9 adjusts only
for gain errors and does not compensate for this offset voltage.