NetComm NWL-12-01 User Manual page 134

Analogue Sensor with Voltage output
There are various analogue sensors that connect directly to the unit which can provide a voltage output. These would require an
external power source which may or may not be the same as the unit itself. The voltage range they provide can be between 0V and
30V. Some common sensor output ranges include 0V to 10V. These would work on the unit, The pull up resistor is not activated in
this case.
Analogue Sensor with 4 to 20mA output
Another common type of sensor type is the 4-20mA current loop sensor. It provides a known current through a fixed resistor,
usually 250 ohms thus producing a voltage of 0v to 5V at the input. The sensor would require an external power source which may
or may not be the same as the unit itself. It will also require an external resistor. The internal pull up resistor is not activated.
Analogue Sensor with Thermistor
Some sensors work by changing resistance due to a change, such as temperature, light etc. These may be wired up to an external
or internal power source and the resistance can be read into the analogue signal. This will require some software calibration like
scaling or offset to map the voltage received to the sensor resistor value. An example below shows the internal pull-up voltage and
1K resistor activated. The voltage received depends on the combination of resistors and the value of the resistance of the sensor
itself.
NetComm Wireless 3G Light Industrial M2M Router
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