Laboratory calibration
1. Prepare a standard thermometer: Select a standard thermometer calibrated by an authoritative metrology agency with higher accuracy as the calibration benchmark. Its accuracy should be at least one level higher than that of the digital thermometer to be calibrated. For example, you can choose a high-precision mercury thermometer or platinum resistance thermometer.
2. Set up the calibration environment: Prepare a temperature-stable environment, such as a constant temperature bath or a constant temperature room. According to the measurement range of the digital thermometer, set the constant temperature device to a specific calibration temperature point. Generally, multiple different temperature points are selected for calibration, such as 0℃, 25℃, 50℃, etc., to comprehensively evaluate the accuracy of the thermometer at different temperatures.
3. Perform comparative measurements: Place the digital thermometer and the standard thermometer in a constant temperature environment at the same time, ensuring that both are in full thermal contact with the environment and are in close position. After the readings are stable, record the readings of the standard thermometer and the digital thermometer.
4. Calculate the calibration coefficient: Based on the readings of the standard thermometer and the digital thermometer, calculate the calibration coefficient or correction value at each calibration temperature point. For example, if at 25°C, the standard thermometer displays 25.0°C and the digital thermometer displays 25.5°C, the correction value for this temperature point is -0.5°C.
5. Adjust the digital thermometer: Adjust the digital thermometer according to the calculated correction value. Some digital thermometers can input correction values through software or hardware settings, so that the thermometer can display more accurate temperatures in subsequent measurements.
Calibration using a calibrator
1. Select a suitable calibrator: There are calibrators on the market that are specifically used to calibrate thermometers, such as dry-type temperature calibrators, thermal resistance calibrators, etc. Select the corresponding calibrator according to the type and measurement range of the digital thermometer.
2. Connection and operation: According to the instructions for use of the calibrator, correctly connect the sensor of the digital thermometer to the calibrator. Then set the required calibration temperature through the calibrator, and the calibrator will generate a stable known temperature signal to simulate the actual temperature environment.
3. Calibration and adjustment: Observe the display value of the digital thermometer at the set temperature of the calibrator and compare it with the standard temperature value of the calibrator. According to the difference between the two, make corresponding adjustments according to the operating manual of the digital thermometer so that its displayed value is consistent with the standard value of the calibrator.
Calibration using fixed points
1. Select fixed point substances: Use some substances with fixed melting points or boiling points to calibrate the digital thermometer. Common ones include the triple point of ice and water (0.01℃) and the boiling point of water (100℃, under standard atmospheric pressure).
2. Make a calibration environment: Take the calibration of ice-water mixture as an example, prepare a clean container, put in an appropriate amount of crushed ice and water, stir evenly, and make a stable 0℃ calibration environment. Make sure that the ice and water are fully mixed and the ambient temperature is stable.
3. Perform calibration operation: Insert the probe of the digital thermometer into the ice-water mixture, and observe the displayed value of the digital thermometer after the reading is stable. If the displayed value is not 0℃, calibrate it according to the adjustment method of the thermometer so that the thermometer displays 0℃ at this point. Similarly, the boiling point of water can be used for calibration at 100°C, but attention should be paid to the effect of ambient air pressure on the boiling point, and air pressure correction should be performed if necessary.
