There are 4 separate parts to this PID:

- The power (polarity does not matter, because it is apparently bridge rectified?)
- The output (The thing that turns on and off in response to meeting the threshold)
- The thermister that measures the value
- The alarm (when the value is reached)

The power has to be connected to both POWER pins, polarity doesn't matter.. but then when it connects to the COM of the Output and Alarm, COM has to be the GND (hence 'common').

Output and Alarm work just like normal relays. They don't get power from the two POWER terminals, it's up to me to connect them to allow current to flow (just like normal relays).

Am I correct in my understanding or is there something else I am missing?

If your power supply has blue/brown wires, simply measure the supply to find out which is positive and which is negative. Sometimes the supplier changes wire color, it isn't really a big deal to measure.

If you don't have a voltmeter, you can use a fan to check the polarity of the power supply.

All of the wiring diagrams I have seen are for either another model of PID or just wrong.

What is the master, correct diagram (ideally with pictures) that I can use as a reference?

I no longer trust writing like 'Terminal X of PID has 2 wires, Terminal Y of PID has 1 wire red' etc etc because the power supply I received and spliced was blue/brown.

The PID device I was shipped was the SESTOS D1S-2R.

Thanks!