SOP - STANDARDISATION OF THERMOMETERS

1.0 OBJECTIVE

To ensure that the thermometers give accurate and reproducible temperature reading.

2.0 SCOPE

This SOP Covers Standardisation procedure of thermometer and is applicable to Quality Control Department.

3.0 RESPONSIBILITY

Officer / Executive.

4.0 ACCOUNTABILITY

Department Head.

5.0 PROCEDURE

5.0.1 The thermometer for calibration shall be mercury in glass type.

5.0.2 Take a 500 ml beaker filled with about 400 ml of Silicon Oil. Use water for (0-50oC) and Silicon Oil for the temperature above 50oC.

5.0.3 Place the beaker on a bath fitted with a stirrer. The stirrer shall be dipped in the beaker leaving about 2 cm space from the bottom of beaker.

5.0.4 Immerse the standard thermometer certified by Approved Laboratory, into the Silicon Oil vertically approx. 8.0 cm leaving the remainder of the stem and the upper expansion chamber exposed to ambient temperature. Clamp tightly.

5.0.5 Immerse the thermometer to be calibrated into the Silicon Oil vertically. The mercury bulb of the thermometer shall be placed at the same level of the mercury bulb of the standard thermometer. Clamp tightly.

5.0.6 Start the stirrer taking precaution that it does not touch the thermometers.

5.0.7 Start heating the oil bath and compare the temperature observed at different increments as given below.

S.No 1
Range of thermometer -10 oC to 50 oC
Set Temp. for Standardization
i. 0 oC
ii. 10 oC
iii. 25 oC
iv. 35 oC
v. 45 oC
Acceptance Limit ± 0.5 oC

S.No 2
Range of thermometer -10 oC to 110oC
Set Temp. for Standardization
i. 0 oC
ii. 25 oC
iii. 50 oC
iv. 80 oC
v. 100 oC
Acceptance Limit ± 1.0 oC

S.No 3
Range of thermometer -10 oC to 250 oC
Set Temp. for Standardization
i. 0 oC
ii. 60 oC
iii. 120 oC
iv. 180 oC
v. 240 oC
Acceptance Limit ± 1.0 oC

S.No 4
Range of thermometer -10 oC to 360 oC
Set Temp. for Standardization
i. 0 oC
ii. 60 oC
iii. 120 oC
iv. 180 oC
v. 250 oC
Acceptance Limit ± 2.0 oC

5.0.8 Any thermometer found beyond the acceptable limit shall be discarded.

5.1 IDENTIFICATION NUMBER

5.1.1 Identification number shall be 10 characters.

5.1.2 The first two characters shall always be “QC” denotes Quality control department.

5.1.3 Third and fourth digits shall always be ‘C’ and ‘T’ respectively. It denotes calibrated thermometer.

5.1.4 Fifth character shall always be hyphen (-).

5.1.5 Sixth and seventh character shall be numeric and denote original number.

5.1.6 The eighth character shall be slash ( / ).

5.1.7 The ninth and tenth character shall be numeric and shall denote number of re-calibration.(version)

5.1.8 A typical example shall be as follows:

Q C C T - 0 1 / 0 0

5.1.9 The thermometer shall have an identification number and standardization date labelled on it.

5.2 CALIBRATION

5.2.1 All thermometers shall be standardized once in a year and calibration record maintained as per annexure-I.

6.0 REASON FOR REVIEW:

First time issue.