RTD temperature probes

Say the wires are 1, 2, 3 and 4.

Select a multimeter, set to low ohms value.

Measure between wire 1 & 2, 1 & 3, 1 &4, 2 & 3, 2 &4, 3 & 4.

There should be four readings in excess of 100Ω and two readings of anywhere between 0Ω and 1Ω.

Which means that 2 of the wires are connected to one end of the resistance, and two to the other.

Now the 4-wire device can be wired to a 3-wire set of terminals correctly, by leaving one lead of the 4-wire device disconnected, and the measurements show which one it can be.

U can go for a normal 3 wire RTD. there should be no problem.but take care about the compensation.

RTDs are usually 3 terminal device. two of which are shorted at the probe for us to calculate the wire resistance of your cable used, so that the 3 wires should be identical and same length to have identical resistance, to get the temperature you should get the resistance of the 2wires and thermistor, then subtract the resistance of the shorted wires. but since the wires are open, you should contact the manufacturer and give the serial number of the device so that they can assist you.

Thank you guest.

The problem is that there are no manufacturers marks and all wires are open circuit.

Four-wire RTD's provide slightly better compensation, but are generally found only in laboratory equipment and other areas where high accuracy is required. When used in conjunction with a 3-wire instrument, a 4-wire RTD will not provide any better accuracy. If the fourth wire is not connected, the device is only as good as the 3-wire RTD; if the fourth wire is connected, new errors will be introduced. Connecting a 3-wire RTD to a 4-wire instrument can cause serious errors or simply not work at all, depending on the instrument circuitry. A 2-wire RTD can be used with either a 3 or a 4 -wire instrument by jumping the appropriate terminals, although this defeats the purpose and reintroduces the un compensated resistance of the leads

I wondered if the red,white, blue colour code signified that they were PT100 or N1000 or somme other range?

From the For-What-It's-Worth department ... got a scanner?

You might hit the jackpot (as I did once) sending a good picture, with a 6" SS pocket rule or other size-reference therein, to a couple of good Source-Contacts. Of course, include ALL available design/operating parameters with the email...

Wishing you success ~

You should be able to figure it out from the instrument end. If you have a decade resistance box it's dead simple. Connect the decade box in place of the RTD, then adjust the resistance until you get a reading of 0°C on the instrument. Then compare the resistance value on the decade box with an RTD standard chart to determine the type of sensor. In some cases, there are 2 or more standard RTD's with the same reference point (for example, there are 2 standard Pt RTD's with 100Ω @ 0°C. In that case you'll need to get temperature readings at 2 different resistance values determine the temperature coefficient of resistivity.

If you can't get a decade box, you can use various fixed resistors (10, 100, 120, 200, 1000Ω) instead.

Try to find RdF(RTD-s maker) web page. But firms do not have the same color codings. So probably last suggestion (using resistance box to identify RTD) is best solution.