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Appendix E – Auxiliary A/D Input Characteristics -- Filter Selection
Filter Selection
J602 controls filtering of the Aux A/D input. With J602 removed, there is no filtering on this input. With J602
in place (the default setting), a single pole RC filter is used to limit noise into the A/D. The nominal cutoff
frequency of this filter is 20 Hz.
Note that source impedances greater than 1 kΩ will appreciably lower this cutoff frequency. When the Aux
A/D input is driven by a source with an output impedance of 1 MΩ, the frequency cutoff will be less than 0.25
Hz.
Aux A/D Specifications
These specifications apply to all PCI4 boards:
Range
Input Impedance
Input Bias Current
Filter Cutoff
±3.276 volts
100 kΩ (approx)
or
10 GΩ (typical)
< 10 nA
20 Hz ± 20%
6-16
J603 & J604 installed
J603 & J604 removed
J603 & J604 removed
J602 in place with
Zsource < 1 kΩ
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