Using the PID test resistor

Using the PID test resistor

We provide a small resistor in the "bits and pieces" bag that can be used to determine the probable cause of issues when the PID is displaying weird or inconsistent temperature readings.

As these odd readings could be caused by either the PID not correctly handling the sensor input, or the sensor not providing a good consistent output - the resistor can be used to provide a good consistent output to allow us to see if the PID displays a good consistent temperature reading or not.

So - take the resistor provided in the bits and pieces bag, and bend with wires roughly as shown below:

Now take the PID controller and remove all wires from terminals 4-10 and the blue wires from terminals 1 and 2 if you have any - being sure to label or otherwise note which wire was connected where for future reference; and for the sake of safety during the test please cover the ends of any bare wires that are still connected to components with electrical tape to prevent any possible damage to you, the machine or the PID components.

You should now have the PID controller with just two red wires connected to terminals 1 and 2.

With the resistor bent roughly as shown above, unscrew terminals 6, 7 and 8 and attach the resistor as shown below ensuring that the bent legs are inserted into terminals 6, 7 and 8 and then screw the terminal screws down tightly.

The PID controller should now look like this:

With the resistor firmly attached as shown above, power the machine / PID on - and the PID display should now show a temperature reading.  This could be almost any value - but it should show a reading and that reading should be consistent and constant and not be fluctuating.

If the reading is consistent and constant then it shows that the PID is properly interpreting the sensor input.  If the reading is fluctuating or jumping up and down then first ensure that the resistor legs are properly connected to 6, 7 and 8 and the terminals are tight - and if it continues then it would indicated that the PID isn't correctly interpreting the sensor input and it may have a fault.

If you are experiencing strange / jumping temperature readings and the test of the PID shows it to be working properly - then the problem is almost certainly either an issue with the sensor wires or a damaged sensor.

To test the actual sensor:  You will need a digital multimeter capable of reading resistance (ohms).  Disconnect the red and white wires from the sensor that are connected to terminals 6, 7 and 8 of the PID and then perform the following resistance readings between the following pairs of wires:

  1. red wire and white wire  (a good sensor should give a good consistent reading typically in the 105-115 ohm range)
  2. the other red wire and white wire  (a good sensor should give a good consistent reading typically in the 105-115 ohm range)
  3. red wire and the other red wire  (a good sensor should give a good consistent reading typically in the 1-5 ohm range)

If the sensor doesn't provide a good consistent reading in the ranges shown above for tests 1-3 above then the sensor is damaged and needs replacing.

If you need further assistance with this issue then please contact us.