Measurement Computing CIO-DAS08-AOH - Manual (Page 27)

The CIO-TERMINAL has the circuitry on board to create custom voltage dividers. The CIO-TERMINAL is a 16" by 4"
screw terminal board with two 37-pin D-type connectors and 56 screw terminals (12 - 22 AWG). Designed for table top, wall
or rack mounting, the board provides prototype, divider circuit, filter circuit and pull-up resistor positions which you may
complete with the proper value components for your application.
8.2 DIFFERENTIAL & SINGLE ENDED INPUTS
This application note uses the CIO-DAS16 as the example board. Please apply the signal names to the board you have.
Two type of analog inputs are commonly found on A/D boards, they are differential and single ended. Single-ended is
typically the less expensive of the two since input connector density is double that for differential inputs.
8.3 COMMON MODE RANGE
Differential inputs have a common mode range (CMR) (Vcm). Single ended inputs have no CMR. Common mode range is
the voltage range over which differences in the low side of the signal and A/D input ground have no impact on the A/D's
measurement of the signal voltage. A differential input can reject differences between signal ground and PC ground.
Shown here is a CIO-DAS16 in differential mode. The multiplexer is omitted for simplicity.
A single ended input has no common mode range because there is only one LOW wire, which is assumed to be the same
voltage at the source and at the A/D board.
The maximum difference which may be rejected is the CMR.
For example, the CIO-DAS16 has a common mode plus signal range of 11.5 volts, common mode not to exceed 10 volts.
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