ADLINK Technology USB-1901, User Manual

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28 Hardware Information
Connection of a floating signal source to the USB-1900 Series
module in pseudo-differential input mode is further shown. For
floating signal sources, the negative side of the signal should
be connected to the AIGND, with less noise coupled into the
signal connections than in single-end mode.
Figure 2-18: Floating Source w/ P-D Input
Current Input Mode (for USB-1903)
The current signal source can be floating or grounded refer-
ence, and will be converted to voltage through a precision
249.5
Ÿ
resistor. Cross voltage on the precision resistor is con-
sidered differential signal. The differential signal pair passes
through differential amplifier buffers and is measured by the
analog-to-digital converter chip (ADC) with +/-10 V input range.
AIxH
AIxL
x = 0, ..., 7
+
To A/D
Converter
AIGND
+
-
-
Instrumentation
Amplifier
Input Multiplexer
Floating
Signal
Source