In many processing plants, particularly within the pharmaceutical
industries, there is a wide range of sensors geared to a company’s individual needs. Often however, these sensors are short and manufactured with a geometrical design that can cause problems during calibration. In general, it is assumed that a sensor must be immersed in a calibration instrument (whether it is a dry block or bath unit) at least 15 times the diameter of the sensor to get an accurate measurement. This means that the sensor's active part must be located in a temperature-homogeneous zone. If this is not possible, other ways must be found to successfully complete the calibration.
One way to get around the issue is to calibrate the sensors using a liquid bath
, but this requires a bath type where the liquid is pumped around axially to ensure temperature homogeneity all the way to the surface. Additionally, there is often a need for "pure" calibration, which means the sensor must not be contaminated with silicone oil or anything else that might be located in the bath. Due to these challenges, liquid bath calibration often does not work for short and sanitary sensors.
An alternative is to calibrate these sensors in a dry block unit.
Read more about sanitary sensors here.