Measurement Computing PPIO-AI08 User Manual

Page 9

4.2.1 Analog Inputs

Analog inputs are Single Ended.

CAUTION

Measure the voltage between the ground signal at the signal source
and the

. Use a voltmeter and place the red probe on the

ground and the black probe on the signal ground. If there is more
than 500 millivolts, do not connect the PPIO-AI08 to this signal
source because you will not be able to make an accurate reading.

Any voltage between the two grounds means that you will create a
ground loop if you connect the signal ground to the CIO-AD board
ground. Current flowing in a ground loop can damage the board
and possibly the computer.

4.2.2 Single-Ended Inputs

A single-ended input is two wires connected to the PPIO-AI08; a channel high (AI# )
and a Low Level Ground (LLGND). The

LLGND

signal must be the same ground the

is on. The AI# is the voltage signal source.

There is no common-mode rejection on a single-ended input so grounding becomes
important for both voltage differentials and noise immunity. If greater amplification or
differential inputs are required, we suggest procuring a CIO-EXP32, for 32 channels
or a CIO-EXP16, a 16-channel analog input multiplexer board.

4.2.3 Digital Inputs & Outputs

All the digital inputs and outputs are

TTL

level.

TTL

is an electronics industry term,

short for Transistor Transistor Logic, with describes a standard for digital signals
which are either near 0V or near 5V.