Chapter 9 SCXI—Signal Conditioning

Table 9-2. SCXI-1100 Channel Arrays, Input Limits Arrays, and Gains

1 Applies if the MIO/AI device supports a gain of 5 (some MIO/AI devices do not).

2 This case forces a smaller gain at the SCXI module than at the MIO/AI device, because the input limits for the next channel range on the module require a small SCXI gain. This type of gain distribution is not recommended because it defeats the purpose of providing amplification for small signals at the SCXI module. The small input signals are only amplified by

a factor of 10 before they are sent over the ribbon cable, where they are very susceptible to noise. To use the optimum gain distribution for each set of input signals, do not mix very small input signals with larger input signals on the same SCXI-1100 module unless you are sampling them at different times.

You can open the AI Hardware Config VI to see the gain selection. After running this VI, the group channel settings cluster array at the right side of the panel shows the settings for each channel. The gain indicator displays the total gain for the channel, which is the product of the SCXI gain and the DAQ device gain, and the actual limit settings. The group channel settings cluster array also shows the input limits for each channel.

LabVIEW scales the input data as you specified, unless you select binary data only. Therefore, the gains are transparent to the application. You can specify the input signal limits and let LabVIEW do the rest.

SCXI Settling Time

The filter and gain settings of your SCXI modules affect the settling time of the SCXI amplifiers and multiplexers. Always enter your jumpered filter settings and your jumpered gain settings (if applicable) in the Measurement & Automation Explorer or the configuration utility. LabVIEW uses the gain and filter settings to determine a safe interchannel delay that allows