Equipment that is using temperature in its process can be found in almost all industries. Almost all these temperature generating equipment have a Temperature Controller installed in them and mostly these are digital temperature controllers.
The temperature controller is not a stand-alone device, it is integrated as a part of a system. They are mostly found on equipment like ovens, incubators, sealers or packaging machines, heaters, dryers, and much more.
Temperature controllers make temperature very stable because of its feedback mechanism in a closed loop circuit. One part is sensing the input while the other part is controlling the output to match the temperature setting.
A temperature controller in order to control a certain temperature needs a sensor, most commonly used sensors are thermocouple wires and RTD. This is one of the best characteristics of a temperature controller, it can be connected to different types of thermocouple or RTD depending on the range and environment where they are installed. It is also an indicator because it has its own display.
When it comes to operation, some are user-friendly which is easy to navigate and connect the input supply while others are very complicated where a user manual is needed to in order to access and operate it.
So as a reminder, always seek first the user manual before operating or making some calibrations, there are so many types of brands or manufacturers of a certain temperature controller and having its manual a priority saves time.
5 Ways to calibrate a temperature Controller
The first method is by temperature simulation (from a calibrator like Fluke 754 and a thermocouple wire) where a temperature source is an electrical signal. (see procedure below)
The second method is through actual temperature by the use of a bath, either dry or wet bath (commonly used is a dry well) where the sensor is dipped in the hole of a well. (see procedure below)
The third is by comparing its reading to a more accurate thermometer or temperature indicator with a separate sensor. In this method, the sensors are clamped, inserted, or fastened by screws into the heat source or heating element. This method is applicable when the sensor or the controller back panel is not accessible. This can be seen in hot surfaces or hot plates. (see sample setup below)
The Fourth is a simulated voltage (in mV), resistance (for RTD) and current like the 4-20 mA depending on the settings or programming of the temperature controller. (mostly related to method 1)
The 5th is by measuring the temperature directly inside an enclosed system using a separate sensor and indicator then comparing its display with the temperature controller. This is usually applied to most ovens or furnace. See this link Ovens
Of course, the easiest is the first one and it is the most commonly used technique. Mostly, the calibration of temperature controllers is a closed loop system, means that you are calibrating a group, not just a controller.
Since a controller needs an input in order to control an output, calibration of both input sensor and its display is already a closed loop calibration, assuming that the sensor used, whether a thermocouple or RTD is permanently connected and used during the calibration process.
