According to the requirements of the calibration points, set the required calibration temperature on the temperature controller of the constant temperature oil bath. For example, if three temperature points of 30℃, 50℃, and 70℃ are to be calibrated, set the corresponding temperatures in turn.

When setting the temperature, it should be adjusted slowly to avoid temperature overshoot. After waiting for the temperature of the oil bath to stabilize, observe the temperature value displayed on the temperature controller. When the temperature fluctuation is within the range of ±0.1℃ (which can be determined according to the actual calibration requirements), it is considered that the temperature has reached a stable state.

Insert the standard thermometer and the calibrated thermometer vertically into the oil in the constant temperature oil bath through the appropriate thermometer socket or bracket. The insertion depth should be as close as possible to the geometric center of the oil bath. Generally, it is required that the insertion depth is not less than 2/3 of the depth of the oil bath to ensure that the thermometer can accurately measure the average temperature in the oil bath.

After the thermometer is inserted, its position should be kept stable to avoid contact with the wall of the oil bath or other objects, so as not to affect the measurement results. At the same time, it is necessary to ensure that the temperature-sensing part of the thermometer is completely immersed in the heat transfer oil.

When the temperature of the constant temperature oil bath is stable, read the indication values of the standard thermometer and the calibrated thermometer at the same time and record them. Read the data once every certain time (such as 5 minutes), and a total of 5 - 6 sets of data are read.

Calculate the difference between the calibrated thermometer and the standard thermometer in each set of data, which is the temperature deviation. Analyze the temperature deviations of each calibration point to judge the measurement accuracy of the calibrated thermometer.

If the temperature deviation of the calibrated thermometer exceeds the allowable range, according to the type and calibration method of the thermometer, make the corresponding adjustment. For example, for an electronic thermometer, it may be necessary to correct it by adjusting the calibration parameters or replacing the sensor.

After the adjustment, calibrate again according to the above steps until the temperature deviation of the calibrated thermometer meets the calibration requirements.