Contec ADI12-8(USB)GY, User Manual

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3. Setup
22
ADI12-8(USB)GY
Measuring current
When using ADI12-8(USB)GY to measuring current, please use a resistance to
convert current to voltage and perform measuring.
You can measure the current output device of 0 - 20mA in the range of 0 - 5V voltage
input by connecting a resistance of 250
Ω
between the [+] input and the [-] input. If
the error of the resistance you use is great, the conversion data would be influenced
and you can fail to obtain the correct measuring result. It is recommended that a
precision resistance(±0.1%) should be used on the connector side.
Furthermore, when several current sources are measured, the potential difference
between their GNDs must not exist.
For ADI12-8(USB)GY, the CPU in the module is isolated from external device
whereas the analog input channels is not isolated each other, therefore, the analog
grounds cannot be connected together.
When the channels are subject to the potential voltage each other, you should use
isolation converter to isolate channels.
- When an analog ground is not connected, the conversion data can be
unpredictable.
- In situations where the connecting cable is subject to noise, accurate analog input
can fail to occur. To avoid this problem, the connecting cable should be installed
away from any source of noise.
- The analog signals that are input into the [+] input or [-] input should not exceed
the maximum input voltage relative to the module analog ground. A voltage
greater than the input voltage can damage the equipment.
- If either the [+] or [-] input pin is not connected, the resulting conversion data can
be unpredictable. If a channel is not connected to a signal source, both its [+]
input and [-] input pins must be connected to the analog ground.
CAUTION