CALIBRATION OF COLD CHAMBERS / FREEZERS

PURPOSE

To establish a Standard Operating Procedure to Calibrate the COLD CHAMBERS / FREEZERS

TARGET GROUP

Engineering Personnel.

MATERIAL & EQUIPMENT

1. Calibrated thermometer.2. Temperature bath.3. Computer with Microsoft excel for error & uncertainty calculation

TYPE OF TEMPERATURE MONITORING SYSTEM1. Digital Temperature monitoring system2. Analog/Manual monitoring system

Based on the monitoring system followed by the organization, one of the following calibration method should be adopted.

Method 1 (Calibration of Digital Temperature monitoring system)

PRELIMINARY INSPECTIONBefore proceeding with calibration, the under test temperature module should inspect the following: Remove the temperature module from the instrument & place calibrated

thermometer for temporary monitoring. Ensure all previous data are saved in the system. Check & ensure that the battery level is full Clean the sensor with 70% alcohol.

PROCEDURE

1. Calibration shall be performed in the controlled calibration room as the ambient temperature 22°C +/- 2°C and humidity between 50% to 75% is maintained.

2. Expose both under test Thermometer as well as the Reference Thermometer to ambient air for 15 minutes.

3. Switch on the temperature bath & wait for 15 minutes to stabilize the temperature.

4. Place both thermometers in the temperature bath & wait for 15 minutes to stabilize the temperature.

5. Let the temperature of the under test thermometer (module) stabilize for one point.

6. The reading of the under test Thermometer as well as the Reference thermometer should be taken.

7. Take the average of 5 readings of 3 different temperatures in the normal operating range & the data shall be filled in the excel format.

8. Calculate the error taking the master’s error in to account9. IF difference > +/- 1°C, adjust the temperature of under test Thermometer

(temperature module).10. Calculate the Expanded Uncertainty & combined uncertainty of all measuring

parameters, uncertainty of master certificate & least count of UUC. Providing a level of confidence of approx. 95%.

11. Affix the calibration sticker on the temperature module.12. Clear the memory of the temperature module & place back in to the respective

equipment.13. Make entry in the service record, update label affixed on the respective equipment 14. Prepare calibration report which should be documented in engineering

department.

Method 2 (Calibration of Analog/Manual monitoring system)

PRELIMINARY INSPECTIONBefore proceeding with calibration, the under test thermometer is inspected for the following: Remove the thermometer from the instrument & place another calibrated

thermometer for temporary monitoring. Cleaned & scales are visible. Entrapped Gases - in the bulb, contraction chamber and expansion chamber. Detached Mercury/Red Alcohol - at the top of the contraction chamber, expansion

chamber and in the stem.In the case one or both of the above faults are observed in the thermometer, such defects are first rectified.Take reference thermometer and the under test thermometer are exposed to the ambient air for 30 minutes kept in the vertical position. Then they are heated to their maximum nominal temperature for 20 minutes. Then both the thermometers are allowed to rest in the ambient air before starting calibration.

PROCEDURE

1. Ensure the ambient temperature 22°C +/- 2°C is maintained.

2. Expose both under test Thermometer as well as the Reference Thermometer to ambient air for 15 minutes.

3. Switch on the temperature bath & wait for 15 minutes to stabilize the temperature.

4. Place both thermometers in the temperature bath & wait for 15 minutes to stabilize the temperature.

5. Let the temperature of the under test thermometer (module) stabilize for one point.

6. The reading of the under test Thermometer as well as the Reference Thermometer should be taken.

7. Take the average of 5 readings of 3 different temperature in the normal operating range & the data shall be filled in the excel format.

8. Calculate the error taking the master’s error in to account

9. IF difference > +/- 1°C, replace the Thermometer and repeat the calibration.

10. Calculate the Expanded Uncertainty & combined uncertainty of all measuring parameters, uncertainty of master certificate & least count of UUC. Providing a level of confidence of approx. 95%.

11. Make entry in the service record, update label affixed on the respective equipment

12. Prepare calibration report which should be documented in engineering department.

REFERENCEClinical and Laboratory Standards Institute (Formerly NCCLS) Laboratory Instrument Implementation, Verification and Maintenance Guidelines GP31-P, Vol. 27 No. 12 for calibration procedure & NABL 141 for calibration measurement