National Instruments AT E Series User Manual
Page 158
Appendix C
Common Questions
C-6
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next channel, for example channel 1, is selected, the accumulated charge
(current) leaks backward through that channel. If the output impedance of
the source connected to channel 1 is high enough, the resulting reading can
somewhat reflect the voltage trends in channel 0. To circumvent this
problem, you must use a voltage follower (op-amp with unity gain) for each
high impedance source before connecting up to the DAQ device or decrease
the rate at which each channel is sampled. Another common cause of
channel crosstalk is due to sampling among multiple channels at various
gains. In this situation, the settling times may increase. For more
information on charge injection and sampling channels at different gains,
refer to Chapter 3,
How are the AI channels of the AT-MIO-64E-3 addressed when they
are used in differential mode?
The 32 differential channel pairs are addressed as shown in the following
table.
How can I use STARTSCAN and CONVERT* on my device to sample
my AI channel(s)?
An E series device employs both the STARTSCAN and CONVERT*
signals to perform interval sampling. The STARTSCAN signal of the
DAQ-STC controls the scan interval (1/scan interval = scan rate) shown
in Figure C-2. The CONVERT* signal controls the interchannel delay
(1/interchannel delay = sampling rate). This method allows multiple
channels to be sampled relatively quickly in relationship to the overall scan
rate providing a pseudo simultaneous effect with a fixed delay between
channels.
Differential Channel Name
I/O Terminals
<0..7>
ACH<0,8...7,15>
<16..23>
ACH<16,24...23,31>
<32..39>
ACH<32,40...39,47>
<44..58>
ACH<48,56...55,63>