Measurement Computing CIO-DAS16/M1/16 - Manual (Page 7)

3.2 ANALOG INPUTS
Connect analog inputs to the board as shown in the following sections. Pay close attention to cabling and grounding
of the shield. Failure to cable as shown will likely result in signal noise.
CAUTION - PLEASE READ
TIP: Measure the voltage between the ground signal at the signal source and the PC. Use a volt meter and place the
red probe on the PC ground and the black probe on the signal ground. If there is more than 10 Volts, do not connect
to this signal source because you will not be able to make a valid reading. If the voltage is over 20 Volts, DO NOT
connect to this signal because it will damage the board and possibly the computer.
3.3 CONNECTING SIGNALS TO THE ANALOG INPUTS
Signal wiring should be done with consideration for the high speed sampling involved. Even if your A/D pacing rate
is not high, the converter is always converting in under 1uS and the internal MUX switching is done at similarly high
speeds. Close attention must be paid to how analog signals are connected to the board.
The CIO-DAS16/M1/16 has eight differential analog input channels. Each channel has a signal high input and a
signal low input. The measurement made by the A/D is the voltage difference between the LOW and HIGH inputs.
Differential inputs have a common mode range (see application note). The CIO-DAS16/M1/16 may have as much as
+11V or -6V of common mode between LLGND and signal LOW.
3.3.1 KEEP HIGH AND LOW WIRES TOGETHER
Keep the signal wires for a channel together. As a minimum, use twisted pair. This will reduce EMI or RFI noise on
your input signal.
3.3.2 SHIELDING
To further protect the input signals from noise, a use shielded wire. Shielded twisted pair is readily available. The
shield should be connected as shown in the diagrams below otherwise ground loops and signals noise may result.
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