- Comprehensive selection for all measuring tasks
Know-how: probe and temperature sensor
There are temperature measurement probes for a variety of media. Their design is different, depending on the task. So, there are different probes for measuring air, on surfaces or in measurement objects. In each of these sub-groups, there are in turn differences in terms of accuracy, response time and measuring range.
Surface probes have a temperature sensor which ensures that the temperature on a measurement object can be determined as quickly and precisely as possible. There are cable probes for almost every measuring task in the temperature measurement range. Their most prominent feature is the cable connection between the probe and the measuring instrument. This transmits the measuring values. The radio probe is the opposite of the cable probe. Here, the measuring values are transmitted wirelessly.
However, no matter what probe is used: they all have a temperature sensor. And in terms of sensors, the following designs can be distinguished:
The measurement of temperatures using thermocouples is based on the thermoelectric effect: electric current flows in a circuit if its cable consists of two different alloys and their contact points have different temperatures. If the temperature at one of the contact points is known (cold junction), the "thermoelectric voltage" present is a direct measure of the temperature difference between measuring point (hot end) and cold junction (cold end).
Platinum resistance sensors
Platinum resistance sensors (Pt 100 sensors) are generally based on the so-called positive temperature coefficient resistor effect (PTC resistor effect). Metals have the characteristic of increasing their electric resistance as the temperature rises. This can be used for temperature measurements.
Thermal resistors or thermistors are modern, inexpensive temperature sensors made from mixed oxide ceramic. Because they have a strong negative temperature coefficient, the term NTC is also used. Their resistance falls as the temperature rises. They therefore behave in exactly the opposite way to Pt100 sensors.