Keithley KUSB-3100, User Manual

Page: 24 / 129

Chapter 2
10
Specifying the Gain for a Single Channel
The simplest way to specify gain for a single channel is to specify the
gain for a single-value analog input operation using software; refer to
page 11 for more information about single-value operations.
You can also specify the gain for a single channel using an analog
input channel-gain list, described in the next section.
Specifying the Gain for One or More Channels
You can specify the gain for one or more analog input channels using
an analog input channel-gain list. Using software, set up the
channel-gain list by specifying the gain for each entry in the list.
For example, assume the analog input channel-gain list contains three
entries: channels 5, 6, and 7 and gains 2, 4, and 1. A gain of 2 is
applied to channel 5, a gain of 4 is applied to channel 6, and a gain of
1 is applied to channel 7.
Input Sample Clock Sources
You can use one of the following clock sources to pace an analog
input operation:
• Internal clock – Using software, specify the clock source as
internal and the clock frequency at which to pace the operation.
The minimum frequency of the internal clock is 30 Hz; the
maximum frequency of the internal clock is 50 kHz.
According to sampling theory (Nyquist Theorem), specify a
frequency that is at least twice as fast as the input’s highest
frequency component. For example, to accurately sample a 2 kHz
signal, specify a sampling frequency of at least 4 kHz. Doing so
avoids an error condition called
aliasing , in which high frequency
input components erroneously appear as lower frequencies after
sampling.