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How to Wire a Thermistor to a Programmable Logic Controller

The mercury thermometer is the most well-known device used to measure temperature, and it is still a standard tool in the collection of meteorological data. In some cases it is useful to collect temperature data electrically, and this can be done through the use of a thermistor which is a resistor whose resistance value changes with temperature. This resistance change can be measured and stored using a programmable logic controller which can take actions when critical temperatures are reached.

Things You'll Need

F1616-BA programmable logic controller
10K thermistor
Personal computer
RS232 cable
Wire
DC power supply

Instructions

- 1
  Plug the power supply lead between the F1616-BA programmable logic controller, or PLC, and the electrical mains. Plug the RS232 lead between the PLC and personal computer. Switch on the personal computer.
- 2
  Using the wire, connect the positive and negative terminals of the DC power supply to the terminals on the thermistor. Connect the output of the thermistor to one of the analog-to-digital convertors of the PLC. The analog-to-digital convertor will measure the voltage dropped across the thermistor.
- 3
  Switch on the DC power supply and set it to output 10 volts. The thermistor is now wired to the PLC and is ready to take measurements.

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