During the calibration process, the thermometer is compared to a known reference source, typically a calibrated thermometer or a standard device such as a fixed point cell or an ice bath. The thermometer is checked at different temperature points to determine if it is measuring accurately, and adjustments are made if necessary.

The calibration process is important because the accuracy of thermometers can drift over time due to various factors such as aging, mechanical shock, and exposure to extreme temperatures. Inaccurate readings can lead to incorrect temperature measurements, which can result in product defects, health risks, and other costly problems.

The frequency of thermometer calibration depends on the industry and application. For instance, thermometers used in the food industry should be calibrated at least once a year, according to food safety regulations. Medical thermometers should be calibrated regularly, depending on their use and manufacturer's guidelines. Industrial thermometers should be calibrated at least once a year, but more frequent calibration may be necessary for critical applications.

A reliable thermometer calibration service provider can help businesses maintain the accuracy of their thermometers and provide calibration certificates to document the calibration process and results.