Temperature sensors by WIKA
For many years, WIKA has been among the leading manufacturers of high-quality industrial temperature gauges. Use temperature measuring instruments from WIKA for the temperature measurement and temperature monitoring of your applications. Our experience and know-how in the manufacture of temperature probes sets us apart. With WIKA, temperature probes in industrial temperature measurement are essentially divided between the following groups:
What is a temperature probe?
The term temperature probe with electrical thermometers, describes a unit from one or more temperature sensors and a usage-specific armour, which can consist of, for example
- connection head
- neck tube
- thermowell or
- a handle
The sensor built into the temperature probe takes the actual temperature measurement and converts the measured temperature into an electrical signal.
When are temperature sensors with thermocouples recommended?
Temperature sensors with thermocouples are suitable for the measurement of high temperatures of up to +1,700 °C (3,092 °F). Thermocouples consist of two different metals which are bound together to form the 'thermocouple'. The connection point (hot junction) represents the actual measuring location of the temperature probe, the wire ends are designated as the cold junction. When there is a temperature change at the measuring location, due to the different electron densities of the metals and the temperature difference, a voltage is generated between the hot and cold junctions. This is approximately proportional to the temperature of the measuring location of the temperature probe (Seebeck effect).
The low diameter of the sheathed thermocouple of a temperature sensor enables a response time that is faster than is possible with a resistance thermometer.
How does the temperature sensor of a Pt100/Pt1000 resistance thermometer work?
A Pt100/Pt1000 resistance thermometer has its strengths in the low and medium temperature ranges of -200 … +600 °C (-328 ... +1,112 °F). In industry, mainly temperature sensors with Pt100 or Pt1000 measuring resistors are used. If the temperature sensor detects an increase in temperature, then its resistance also increases (positive temperature coefficient). The resistance of a Pt100 resistance thermometer at 0 °C (32 °F) is 100 ohm, for a Pt1000 resistance thermometer it is 1,000 ohm. Further information on this can be found in our video "How does a resistance thermometer work? | Resistance thermometers per IEC 60751".
What types of measuring resistors are there in temperature sensors?
Basically there are two types of measuring resistors differentiated in temperature probes: Thin-film measuring resistors and wire-wound measuring resistors.
The advantages of thin-film measuring resistors are their small overall size and high vibration resistance with the appropriate construction of the temperature sensor. Thin-film measuring resistors have come to represent the standard sensor design, provided that they are not ruled out as a result of their temperature range (measuring ranges for accuracy class B temperature probes: Thin-film measuring resistors -50 … +500 °C / -58 ... +932 °F, wire-wound measuring resistors -200 … +600 °C / -328 ... +1,112 °F). Thus, wire-wound measuring resistors have advantages in lower and medium temperature ranges.
When is it suitable to use surface thermometers?
Surface thermometers are suited to the non-contact measurement of temperature on the surfaces of vessels or pipes. They are designed as resistance thermometers (TR50) or thermocouples (TC50). The latter enable an exact measurement of extreme temperatures between -40 to +1,200 °C (-40 ... +2,192 °F). Both variants are available with explosion protection.
Surface thermometers feature problem-free installation without thermowells. The mounting to vessels is achieved using a welded-on or screwed-on contact block which contains the temperature probe. For fixing to pipelines, a variant with tightening strap is suitable. Centrally bored washers and metallic weld-pads are available as further process connections. For specific ambient conditions, the connection leads of the surface thermometers can be delivered with special insulation materials. The cable end can be delivered ready for connection or with fitted plug (optional) or with a field case.
