Calibration by means of an external standard thermometer

The WIKA standard thermometers are particularly suited for applications in industrial laboratories. They enable easy comparative calibration in our baths, in tube furnace and in dry well calibrators.

The use of an external reference thermometer is recommended, particularly for the calibration of short temperature sensors. Thus the errors due to the radial and axial temperature distribution in the temperature conditioning unit are considerably reduced.

For calibration, the test items and the standard thermometer are brought to the same temperature in a temperature conditioning unit. As soon as a stable temperature is reached, the test items are read or their output signals are measured (resistance, thermoelectric voltage, standard signal) and compared with the standard thermometer. Using this comparison method, the measuring uncertainty can be considerably reduced because not only the display of the temperature conditioning unit is taken into consideration.

Thermocouple model CTP9000

Features

The standard thermometer is a type S element whose nominal composition consists of Platinum-10 % Rhodium (positive leg) against Platinum (negative leg) and belongs to the group of noble thermocouples. It is characterised by its high stability.

The quality of the thermowell used is essential for stabil - ity at high temperatures. For this reason, the high-purity aluminium oxide ceramic C 799 is used.

The type S thermocouple, besides the low ageing drift, also offers the advantage of a low basic tolerance.

Measuring technology

During measurement it must be ensured that the compensating leads from the measuring point to the cold junction consist of substitute materials which have, in a limited temperature range, the same thermoelectric properties as the materials of the thermocouple. Therefore, at this transition, there is no thermoelectric voltage.

This voltage is only generated at the point where the Thermocouple model CTP9000 compensating leads are connected to normal copper leads.