Temperature Calibration
An understanding of the proper tools used for the calibration of transmitters is required for an Instrumentation Technician. There is such a wide variety of calibration tools used in industry. Today I will highlight some of the more common calibration tools used on Temperature transmitters.
Dry Block
A Dry Block is a temperature-controlled device used to calibrate temperature transmitters. It looks like a box and has a sleeve with multiple holes. These are where you insert your sensors.
First, I will set the Dry Block to the lower range value for our transmitter. Next, I’ll place my sensor and a thermometer in the Dry Block. The thermometer is used so we’ll have a more accurate temperature reading. It takes a little while for the Dry Block to heat up. Once the thermometer is reading the lower range value it is time to adjust the zero on the transmitter. Next, I’ll repeat the procedure for the upper-ranged value and I’ll adjust the span this time. Finally, I’ll do my 5-step verification.
Some benefits of a Dry Block are that it can reach a wide variety of temperatures and it is portable.
Micro Bath
The Micro Bath is similar to a Dry Block except instead of putting the sensor into a well you immerse it in a temperature-controlled liquid.
First, fill the tank with a liquid, typically silicone oil or water. Next, you’ll want to place the sensor and thermometer in the tank, ensuring that both are completely submerged. Now you can set your temperature and adjust your zero and span values. Make sure you give the sensor time to stabilize before playing with your zero and span.
Some benefits of the Micro Bath are that it allows you to calibrate more transmitters at a time and more awkward-shaped sensors unlike the Dry Block.
Temperature Simulator
A much more simple and portable option is the temperature simulator. It is a process meter that can simulate both RTD’s and Thermocouples. You just select which RTD or thermocouple you’d like to simulate and hook it right up to the temperature transmitter. If using a Thermocouple, make sure you have the right polarity coming from the meter to the transmitter. If using a RTD, make sure that you have the correct Next, select the temperature you’d like to simulate and now you are free to set your zero and span.
Some benefits of a temperature simulator are its portability as well as its versatility.
After you have completed your zero and span adjustments it is important to perform a five-point calibration. Check out our article on how to perform one!
