Measurement Computing CIO-EXP-GP - Manual (Page 16)

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Each input circuit has eight screw terminals associated
with it. These terminals are shown in Figure 4-4 to the
right.
To connect a voltage signal to the input circuit you
need only use three screw terminals. These are:
+SENSE Signal high, or CH HI on a DAS board
−
SENSE Signal low, or CH LO on a DAS board.
Must be jumpered to
−
P for single-ended
−
P Low Level Ground (LLGND)
Figure 4-4. Input Screw Terminals
4.7.1 Single-Ended Inputs
A single-ended input has two wires connected to the CIO-EXP-GP; a signal high and a Low Level
Ground (LLGND). The LLGND signal must be the same ground the PC is on. Single-ended mode is
selected by installing a jumper between the signal low (
−
SENSE) and ground (
−
P). The -SENSE
terminal is then connected to the signal ground and the +SENSE terminal is connected to the signal.
4.7.2 Floating Differential
A floating differential input has two wires from the signal source and a 10K ground reference resistor
installed at the CIO-EXP-GP input. The two signals from the signal source are Signal High and Signal
Low. The reference resistor is connected between the CIO-EXP-GP “
−
SENSE” and “-P” pins and the
Signal Low is connected to the -SENSE terminal. The +SENSE terminal is connected to the Signal High.
A floating differential hookup is handy when the signal source is floating with respect to ground, such as
a battery. The floating differential input will reject up to 10V of EMI energy on the signal wires.
CAUTION: Is the signal source really floating? Check it with a voltmeter before risking the
CIO-EXP-GP and PC.
4.7.3 Fully Differential
A differential signal has three wires from the signal source. The signals are Signal High, Signal Low and
Signal Ground (LLGND). Signal High is connected to the +SENSE terminal and Signal Low is
connected to the -SENSE terminal. The ground reference must be connected to the -P terminal.
A differential connection allows you to connect the CIO-EXP-GP to a signal source with a ground that is
different than the PC ground, but less than 10V difference, and still make a true measurement of the
signal. For example, a laboratory instrument with its own wall plug. Sometimes there is a voltage
between wall outlet grounds.
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