Temperature probe with Temperature PT100 Sensors

Particularly in surface treatment, the precise measurement and control of temperatures is of decisive im- portance for the subsequent quality of the treated items. To keep the temperature of the liquid in storage tanks within the desired range, also prevents negative effects on the process liquids, such as freez- ing, crystallisation and excessive viscosity.

The following functions need to be implemented:

• Control of the temperature inorder to automate process steps (such as keeping the desired process temperature)

• Monitoring of the temperature in order to avoid possible damage to the process, the process liquid (e.g. damage by excessive tem- peratures) and the tank (e.g. thermal damage)

With the aid of temperature sen- sors and suitable electronic units, you can control and monitor the temperature of liquids easily and cheaply.

Our temperature sensors are avail- able in the following versions:

• with rigid immersion tubes madeof various materials

• with flexible tube made of PFA

All versions can be equipped withone, two or three Pt 100 elements. Other temperature sensors specified by you can also be integrated.

The function of the temperature sensor results from the integrated

Pt 100 sensor element. The tem- perature is determined from the temperature-dependent change in the electrical resistance of the Pt 100 element. At 0°C, the elementhas a resistance of exactly 100 Ω.As the temperature increases, theresistance of the element changes in direct proportion to the temperature change.

A suitable electronic unit generatesa low, constant current through the Pt 100 element and measures the resulting voltage across the element. The resistance of the element, and thus its temperature, can then be determined with the aid of Ohm’s Law (R = U/I).

The connection between the electro- nic unit and the Pt 100 element can be made with 2, 3 or 4 wires. We provide 4-wire connections because these permit compensation for the resistance of the connecting wires.

Particularly in the case of long wires, the measurement result can be significantly distorted by the wire resistance. Therefore, the connection of temperature sensors to electron- ics should not exceed 50 m and should be executed generally with 3 or 4 wires. For longer lengths, it is possible to interpose a temperature transmitter with a standard outputsignal of 4...20 mA.

Temperature sensors with a flexible protective tube made of PFA (∅ 6 mm) with a standard length of 1.6 m (other lengths possible) are extremely resistant to chemicals and the maximum operat-ing temperature is 200°C. They arealso suitable for use in cleanroom applications (physiologically benign) and can be mounted to the measur- ing point in plants and tanks where space is limited. The Pt 100 sensor element, with an active measuring length of 50 mm, is mounted to the end of the protective tube.