Pt100 Probes

The Pt100 is at a slight disadvantage in terms of resolution and signal strength. The base resistance of the Pt1000 is 10 times higher – so the unwanted resistance from lead wires has less influence on the measurement than with a Pt100.

On the other hand, the power loss of the Pt100 is lower for the same measuring current, so it heats up less. However, the self-heating of the Pt1000 can also be counteracted by a lower measuring current.

The resistance of the connecting cable distorts the result result of the measurement: with a Pt100, this distortion is pretty significant at about 0.4 Kelvin per metre of cable length. With a Pt100, we therefore recommend a 3- or 4-wire circuit for cable lengths of more than 1m.

Alternatively, you can either use a Pt1000, or use a transmitter as close as possible to the sensor, or directly use a temperature sensor with 0-10V/4-20mA output signal.

The output signal of a Pt100 is comparatively weak and therefore sensitive to interference. Amplification or conversion of the signal to a more robust one such as 0-10V or 4-20mA is therefore often recommended, especially when using longer cables. Our integrated transmitters also compensate for the measuring error and thus improves the accuracy.

You need a digital output signal? Take a look at our Modbus temperature sensor series!

Generally speaking, Pt100 sensors are comparatively accurate. The resistance values and accuracy classes are defined in DIN EN 60751 and IEC 751. Class AA is the one with the highest accuracy, class C the one with the lowest.

However, the accuracy of an individual sensor depends not only on the accuracy class of the measuring element, but also crucially on the cable length and the cable configuration (2-, 3- or 4-wire circuit) as well as the measuring current. As you can see: the devil is in the details. Our experts are happy to help you choose the right temperature sensor – get in touch now!

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Regarding the response time of a sensor, the following rule of thumb applies: If you double the diameter, you quadruple the response time. So choose the diameter wisely!

As with all temperature sensors, the immersion length should be at least 5x the diameter of the sensor to avoid thermal bridges.