4 wire Pt100 probe to 2/3 wire temperature controller 1

[MikiBg]

Hi all.
We have 4 wire Pt100 probe for submersible pump motor protection and temperature controller which supports 2 or 3 wire measurement installed on the site.
What is the best way to adapt the probe to controller? I have found some drawings online suggesting 2 wire connection of 4 wire probe, simply by shortening of the wires at the same side of the probe, but I'm not sure will it be working properly. Haven't found nothing about 3 wire connection of 4 wire probe.
Any experiences about the subject?

 

[markstg]

Connect the 4 wire RTD as a 3 Wire, and use the 3 wire connection at the controller.

 

[btrueblood]

Agree with markstg. Most accurate connection possible for that situation is 3-wire.

 

[Compositepro]

The principle of a four wire RTD is that one pair of wires carries current to the RTD and a second pair is used to measure the voltage drop across the RTD (no current in the sense wires). This eliminates the error caused by voltage drops due to current flow through the wires. A three wire set-up can measure the voltage drop across one power wire and then assume the other power wire has the same drop. This is close to the same accuracy as a four-wire set-up. A two wire set-up cannot eliminate errors in lead resistance and becomes inaccurate as the wires get longer. However, if you have four wires then hooking them up so you have two wires in parallel will cut the wire resistance in half, and reduce error compared to just using two wires. You would only do this if your instrument will not take a three-wire or a four-wire input.

 

[LionelHutz]

In case it's not clear,
4-wire is a resistor element with 2 wires connected to each end.
3-wire is a resistor element with 1 wire connected to one end and 2 wires connected to the other end.
2-wire is a resistor element with 1 wire connected to each end.

So, to convert from 4-wire to any other configuration you can just parallel or ignore the extra wires. I would suggest you do as follows,

Connect the 2 wires from each end of the element together to parallel the wires if using the 2-wire connection.

Use 3 of the 4 wires if using the 3-wire connection. There will be a bigger error in the compensation for the lead length if you connect the 4th wire in parallel on the side of the element that only has a single connection.

 

[MikiBg]

Thank you for advices.
Regards,
Miki