Why do I need to calibrate?
Correct and reliable measurements are the basic requirements of every high-quality industrial production. Vibrations, chemical influences and frequent changes of temperature lead to deviating measured values. Even the best quality temperature sensors eventually drift. Regular calibration is the only way to obtain information about differences between the actual temperature and the measured temperature. With a mobile temperature calibrator, you can make calibrations precisely and simply, directly on site – in no time at all.
Checking and documenting the accuracy of a device under test against a reference sensor describes the calibration procedure. For a temperature calibration, a reliable reference temperature is generated using an independent heat source – a temperature calibrator. By comparing the calibrator display with the device under test display, you can determine the deviation. In general, the displayed value (device under test) is deducted from the “true value” (calibrator). Checking four to six temperature points is recommended.
Why it’s worth buying a temperature calibrator
Machine downtime during calibration costs time and money. This is why we have developed the fastest temperature calibrators which shorten the calibration duration by up to 50 %. Instead of removing the temperature sensor and sending it to an external calibration service provider, you can calibrate the entire measuring chain with a temperature calibrator: sensor and display.
Whether on site or for stationary applications, the temperature calibrator checks different devices under test such as temperature sensors, temperature switches, safety temperature limiters or thermometers.
The right choice of calibrator
Inserted, surface or infrared temperature sensor: the choice of sensors to use is expanding, and as a consequence, the tasks covered by temperature calibration technology are becoming more and more extensive. The right choice of calibrator saves costs and simplifies working processes. This is why it’s all the more important to find out which model performs the desired tasks.
When buying a temperature calibrator, you should always pay attention to the following main selection criteria: does the calibrator cover the desired temperature range? Should the device only have the heating function, or should it also have an active cooling function? To which decimal place precisely should the values be shown? Which model suits the devices under test based on their size and design?
We generally distinguish between dry block calibrators and calibration baths. As the product name suggests, dry block calibrators have a metal block which holds the test specimen – calibration baths have a liquid tank. The heating elements for generating the temperature are located in the block or tank which is insulated on the outside. An electronic controller is used to set and regulate the temperature. The reference sensor determines the actual temperature. The sensor should be calibrated to the temperature point at which it is used as well. This is why when purchasing the calibrator, you should ensure that it covers the temperature range of the temperature sensor to be tested and that it can generate all important test points.
Dry block calibrators are especially well suited to high temperature ranges, straight and long devices under test as well as calibrating without liquid. The calibration baths are used for short devices under test with particular designs. If the tester wishes to calibrate a large number of sensors at the same time, a block diameter of 60 mm is available. However, if the tester wishes to calibrate a small number of sensors in a short period of time, the block diameter of 28 mm is suitable.
If the calibrator is to calibrate various device under test types, the multi-functional calibrators from the TP Premium series present a clever solution, as they combine four applications into a single device. The user can simply switch between dry block, bath, infrared and surface sensor calibrator at any time without any great effort or additional help.
To sum up: the required temperature range and the diameter, length, quantity and measuring principle of the devices under test are decisive when it comes to selecting the model. With their production and development sites in Germany, SIKA offers a wide range of products from robust service calibrators right up to high-end lab equipment.
Tips and tricks when calibrating
Before all important temperature points are checked, the temperature sensor’s suitability for calibration must be checked. To do this, the extreme points are tested.
You must ensure that the device under test is coupled to the block correctly to ensure an ideal heat supply. Calibration insert bore holes are available from between 1.5 mm and 25.5 mm – in 0.5 mm increments. The right material is normally stated by the manufacturer. When using a calibration bath, you must make sure a suitable calibration liquid is used – the right calibration liquid depends on the temperature.
If you are calibrating using an external reference sensor, this is dipped into the metal block with the device under test. Here, both sensors should be at the same immersion depth. To obtain a correct calibration result, the calibration must only be carried out once the device under test has reached the temperature of the calibration insert.
The duration of the calibration procedure depends on how high the selected temperature is. Important quality features are therefore the heating and cooling time of the calibrator, to reach the selected test temperature as quickly as possible and to keep it stable.
The more devices under test that can be calibrated at the same time, the less time required for the entire calibration procedure.
By using calibration software, you can carry out a fully automated test, right up to automatically preparing the calibration certificate – this saves time and money.
To always ensure a reliable test, the temperature calibrators should be recalibrated after 500 operating hours or three years have elapsed. We offer this procedure in our own certified DAkkS lab.