OBJECTIVE:
To lay down the procedure for Operation and Calibration of Thermometers
SCOPE:
This procedure is applicable for the Operation & Calibration of Thermometers in Quality Control Laboratory.
RESPONSIBILITY:
Quality Control Officer / Executive are responsible to follow procedure as per the procedure mentioned in this SOP.
QC Head is responsible for implementation and compliance of the procedure as per this SOP.
ABBREVIATIONS
SOP : Standard Operating Procedure
QC : Quality Control
PROCEDURE:
Procedure For Operation:
Observe the temperature of the sample under test up to the least count of the thermometer available as per required temperature range visually.
Ensure that before using the thermometer is calibrated and validity date of the calibration is not due on the date of observation.
The thermometer shall be placed back with its cover at the proper place after use.
Procedure For Calibration:
Calibration of a thermometer should be performed by the procedure mentioned below :
Take superior quality thermometers (Zeal make) capable of measuring temperatures (a) from -50°C to +50°C, (b) from -10°C to 110°C, (c) from 0°C to 250°C.
Calibrate thermometers at a single point in the following ranges:
For -10°C to 110°C at 15°C to 25°C, 45°C to 55°C and 95°C to 105°C.
For 0°C to 250°C at 45° to 55°C, 145°C to 155°C and 240°C to 250°C.
Take a NPL (National Physical Laboratory) calibrated and certified thermometer or any thermometer traceable to National standards.
For calibrating the thermometer at 15°C to 25°C, place both the thermometers in a vessel containing cool water and observe the temperature displayed on both the thermometers.
For calibrating the thermometer at 45°C – 55°C, 95°C – 105°C, 145°C – 155°C and 240°C –250°C, dip the calibrated thermometer in an oil bath and set the temperature of the bath to the desired temperature. Simultaneously check the temperature value displayed on the calibrated thermometer. Keeping the temperature of the oil bath maintained, dip the thermometer required to be calibrated into the oil bath. Note the temperature value displayed on the thermometer. The difference of temperature between the two thermometer should not be more than ± 1°C.
Acceptance Criteria of A Thermometer
A thermometer shall be suitable for use only if the difference of temperature values between the calibrated thermometer and the thermometer undergoing calibration is not more than ±1°C.
Frequency of Calibration
Any thermometer calibrated by NPL or any other accredited laboratory shall be sent back for recalibration before its due date of calibration (till such time another calibrated thermometer shall be available for use). However, thermometers calibrated in-house shall be verified for their proper functioning once every three months.