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4-10
Cabling and Wiring
Connecting Signals
This section contains precautionary advice to consider before making I/O
connections. The section also shows some circuits for wiring signal
sources to input channels of DAS-1800HC Series boards.
While the circuit diagrams show direct connections to channel input pins
of the main I/O connector, you must make actual connections through
corresponding inputs of an STA-1800HC or STP-100. Refer to Appendix
B for a list of these inputs and their descriptions.
The circuit diagrams represent a single signal source wired to a single
channel (channel
n
). In reality, you can wire 32 separate signal sources to
32 differential inputs or 64 separate signal sources to 64 single-ended
inputs.
DAS-1800HC Series boards contain separate grounds for analog and
digital signals. An analog ground (AGND) is for analog signals and
analog power; a digital ground (DGND) is for digital signals and other
power-supply returns.
Precautions
If you expect to use DAS-1801HC boards at high gain, read the
precautionary information in the following subsection. Other
considerations for I/O connections are offered under “Additional
Precautions” on page 4-11.
Precautions for Using DAS-1801HC Boards at High Gain
Operating a DAS-1801HC at a gain of 250 can lead to problems if your
application is unable to cope with noise. At a gain of 250, each bit of A/D
output corresponds to 10µV of analog input. Thus, with the high speed
and bandwidth of this board, analog noise and performance degradation
come easily unless you take precautions to avoid them. The following
collection of ideas and suggestions is aimed at avoiding these problems.
●
Operate a DAS-1801HC in 32-channel differential mode. Using the
board in 64-channel, single-ended mode at high gains introduces
enough ground-loop noise to produce large fluctuations in readings.
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