1、 Preparation before operation

1. Environmental condition control
   • temperature stabilityThe temperature fluctuation of the verification environment should be controlled within ± 0.1 ℃ (when high-precision is required), avoiding direct sunlight, airflow, or heat source interference.
   • humidity controlIt is recommended to maintain a relative humidity of 30%~70% to prevent condensation or static electricity.
   • Vibration isolationThe device should be placed on a shock-absorbing platform, away from vibration sources such as air conditioning and motors.
   • cleanlinessThe verification area should be free of dust and oil stains to avoid contaminating the thermometer or standard source.
2. Equipment inspection
   • Standard source calibrationConfirm that standard thermometers (such as platinum resistance thermometers and standard platinum rhodium 10 platinum thermocouples) have been calibrated by higher-level metrology institutions and are within their validity period.
   • Device statusCheck the temperature uniformity and stability of equipment such as constant temperature bath and dry well furnace (such as constant temperature bath fluctuation ≤ ± 0.02 ℃/30min).
   • Connection line inspectionEnsure that the thermocouple compensation wires and transmission lines are not damaged, have good contact, and avoid signal interference.
3. Pre treatment of the tested thermometer
   • Cleaning treatmentWipe the temperature sensing part of the thermometer with anhydrous ethanol to remove oil stains or oxides.
   • status checkConfirm that the thermometer has no mechanical damage, open circuit, or short circuit (for electrical thermometers).
   • Pre cooling/preheatingAccording to the type of thermometer (such as a glass liquid thermometer that needs to be placed vertically for 10 minutes, and a thermocouple that needs to be powered on for preheating).

2、 Precautions during operation

1. Insertion depth and position
   • Immersion of temperature sensing elementThe temperature sensing part of the thermometer needs to be immersed in a calibration medium (such as constant temperature bath liquid, dry well furnace metal block), with a immersion depth of at least 15 times the diameter.
   • Avoid thermal interferenceThe distance between thermometers and between thermometers and container walls should be ≥ 30mm to prevent thermal conduction or radiation interference.
2. Temperature point selection and stabilization time
   • Checkpoint coverageSelect at least 3 calibration points (such as low temperature, medium temperature, and high temperature) based on the thermometer range, covering the range of use.
   • stabilization timeAfter the constant temperature bath reaches the set temperature, it is necessary to wait for the temperature to stabilize (such as temperature fluctuations of ≤± 0.01 ℃/5min) before recording the data.
   • Reading timeGlass liquid thermometers need to wait for the liquid column to stabilize (usually 3-5 minutes), and digital thermometers need to confirm that there is no fluctuation in the display.
3. Data recording and processing
   • Multiple measurementsMeasure at least 3 times at each checkpoint and take the average to reduce random errors.
   • Correction value calculationRecord the difference between the reading of the tested thermometer and the standard value, and draw a correction curve or table.
   • Uncertainty assessmentConsider factors such as standard source error, environmental fluctuations, insertion depth, etc., and calculate the uncertainty of the verification results.

3、 Post operation maintenance

1. Equipment shutdown and cleaning
   • Standard source protectionAfter the verification is completed, first turn off the standard source heating/cooling function, and then turn off the power after the temperature drops to room temperature.
   • Media processingThe liquid in the constant temperature bath needs to be replaced regularly (such as replacing silicone oil every 6 months) to prevent contamination or oxidation.
   • Equipment cleaningWipe the surface of the device with a soft cloth and avoid using corrosive cleaning agents.
2. Data archiving and reporting
   • Preservation of original recordsRecord the verification date, environmental conditions, standard source information, verified thermometer number, and verification results.
   • Report PreparationProvide a verification certificate, specifying the correction value, validity period (usually 1 year), and usage restrictions.

4、 Safety and Maintenance

1. Electrical safety
   • grounding protectionEnsure that the device is well grounded to avoid the risk of electrical leakage.
   • Explosion proof measuresUse explosion-proof thermometer calibration device in flammable and explosive environments.
2. Personnel protection
   • high-temperature protectionWear insulated gloves when operating high temperature calibration points (such as>100 ℃) to prevent burns.
   • Low temperature protectionWhen operating low-temperature calibration points (such as<-20 ℃), avoid direct skin contact with metal parts to prevent frostbite.
3. regular maintenance
   • calibration cycleIt is recommended to calibrate the standard source every 1 year and check the overall performance of the device every 2 years.
   • troubleshootingIf abnormal temperature fluctuations or display value drift are found, it is necessary to check the heating/cooling components, sensors, or control circuits.