Pt100 Measuring resistor

The scale for measuring temperatures

Resistance thermometers with a Pt100 sensor are very important in temperature measurement. The sensors made with platinum change their degree of resistance according to the temperature. The resistances are divided up according to accuracy into the classes A, B and AA, as per IEC 60751:2008.

A distinction is also made as to whether a single or double Pt100 is needed. With a double Pt100, two measuring resistors are installed next to each other in a single thermometer. This arrangement is needed if two signals are being processed. The signal from the first Pt100 measuring resistor is used for the control, for example, and the signal from the second Pt100 is used for the display device.

Many different designs, depending on the area of application

Of note here are the Pt100 screw-in resistance thermometers, which are also known as screw-in Pt100 temperature sensors. These feature a sensor consisting of a stainless steel housing equipped with a thread, making it suitable for screwing into threaded holes. This produces a fixed, defined position of the measuring point.

A further version of the Pt100 temperature sensor is the Pt100 surface resistance thermometer, also known as a Pt100 surface sensor. As the name suggests, this is designed to measure surface temperature using a Pt100.

Pt100 temperature sensors are also used as Pt100 sheathing resistance thermometers. In this instance, the Pt100 measuring resistor is installed in a mineral-insulated solution and weld-sealed at the front. A sheathing resistance thermometer can be bent along its length.

To process the output signal produced by a Pt100 thermometer, for example to connect it to a PLC, a Pt100 transducer is required. A signal of 4-20 mA is then output or, in the case of a Pt100 transducer, 0-10 V.

Interesting facts about PT100 resistance thermometers

Numerous types are listed under the generic term Pt100 resistance thermometer. First of all, a distinction is made as to whether it is a single or double Pt100. With the latter, two Pt100 sensors are installed directly next to each other. This type of Pt100 temperature sensor is required wherever two signals have to be processed. The signal from the first Pt100 thermometer is used for the control and the signal from the second Pt100 thermometer for the display device.

Another criterion is the accuracy class. A distinction is made between Pt100 classes A, B and AA – but class AA is better known as 1/3 DIN.

There are also Pt100 sensors that are provided with a thread. These are colloquially called screw-in Pt100 or screw-in resistance thermometer Pt100.

Another well-known version of the Pt 100 sensor is the Pt100 surface sensor. As the name suggests, this should measure the surface temperature using a Pt-100. However, this often turns out to be difficult in practice, since the sensors are usually installed in a round housing and therefore cannot achieve a good measurement result. However, there are also Pt100 surface probes in which the Pt wire is attached to a Kapton foil. These sensors are much better suited for surface temperature measurement than those built into round housings, but the costs for this type of Pt100 sensor are significantly higher.

An extensive group of the Pt100 temperature sensors belongs to the Pt100 jacket resistance thermometers. Here the Pt100 temperature sensor is installed in a mineral-insulated cable and welded tightly at the front. The great advantage of a Pt100 temperature sensor of this type is that on the one hand you can bend the mineral-insulated cable behind the built-in Pt 100 temperature sensor, but on the other hand it has the positive properties of a rigid housing and so combines the two very well.

In order to process the output signal that a Pt100 thermometer outputs – for example to connect it to a PLC – a Pt100 measuring transducer is required. A signal of 4–20 mA or, in the case of a Pt100 measuring transducer, 0-10V is then output.

All Pt 100 sensors can be extended using a plug. However, there are no special Pt100 connectors. Instead, Lemo plugs or M12 plugs and thermocouple plugs with Cu-Cu contacts are preferred.

In conclusion, our experts would like to make a note: What does not exist, but is requested more often, is a Pt100 thermocouple or a Pt100 thermocouple. Two terms are combined here, but they describe two different measurement methods: on the one hand, that of a Pt100 temperature sensor and, on the other hand, of a thermocouple, which, in contrast to the Pt100 resistance thermometer, does not display a change in resistance, but rather generates a thermal voltage. And this only applies to thermocouples.

When it comes to quality, i.e. precision and longevity, the Pt100 resistance thermometers from Therma Thermofühler GmbH are the benchmark for the highest demands. And that with an excellent price-performance ratio.

In our professional online shop you can get the Pt100 temperature sensors in all imaginable classes (class B, class A, class AA or 1/3 DIN), different lengths of element and connection cable as well as circuit type (2-wire technology, 3-wire technology, 4- Head of Technology). Different connections (free ends, Lemo plugs, Lemo couplings) and cable types / cable materials (Teflon, glass fiber) can also be selected.

And for everyone who also needs a very special solution, we also offer the right Pt100 resistance thermometer for small quantities and even individual one-off productions at low cost.