PT100 Thermometer Probes

[Munroast]

Not sure what forum to ask this in, so will try here.

I am wishing to replace a PT100 thermometer probe, the one I have is a two wire, all I can find to buy are 3 & 4 wire. Can anyone explain why any thermometer probe would require more than 2 wires?

Its to connect to a Lae MT6 display

 

[maltaron]

There are plenty on e-bay

 

[Munroast]

There are plenty on e-bay

There are plenty of THREE wire ones on ebay - or did you mean that there are lots of answers to my question?

 

[Aunsh]

The use of more than two wires is to reduce the measurement error due to the connecting leads.

Four-wire connections tend to be used for the most accurate sensors, where two wires carry the precision sensing current and two wires connect the sensed voltage back to the meter, normally a wheatstone bridge or four-wire Kelvin circuit.

Three-wire sensors will have two wires connected together at one end of the sensing element and one wire connected at the other end. The accuracy of the lead wire resistance match affects the measurement accuracy.

Two-wire sensors provide the lowest accuracy, as the resistance of the leads affects the measured resistance value.

You should be able to use a three-wire sensor as a two-wire, simply by ignoring one of the two wires which will be connected together at one end of the sensing element.

Hope that helps.