SOP for Operation and Calibration of pH Meter | Working Principle of Crockmeter


1.1 To lay down the procedure for pH METER.

2.0  SCOPE

2.1 This procedure applies to Quality Control Department. 


3.1 QC Chemists Lab analysts follow the SOP.

3.2 Head- QA, and QC for implementation of SOP.

4.0  pH meter calibration procedure

4.1 Ensure that the pH meter is calibrated.

4.2 Clean the electrode with dry tissue paper.

4.3 As per testing procedure take sufficient sample qty. into a 100ml beaker.

4.4 Stir well to make a uniform suspension.

4.5 Immerse the electrode into the suspension/sample.

4.6 Switch on the pH meter and read the pH.

4.7 Record pH (Express the reading as a number) reading in an analytical register.

4.8 Wash the electrode carefully with distilled water and dip the electrode into the distilled water between uses.

5.0  PRECAUTION For pH meter

5.1 Ensure that the instrument is cleaned before and after use.

5.2  Handle glassware & Glass electrodes carefully.


           SOP:           Standard Operating Procedure

            QA:           Quality Assurance

QC:           Quality Control



Working Principle of Crock meter

1 The crock meter consists of a rigid flat metallic platform on which the test specimen can be held firmly and an abrading finger that rubs against it under a specified load. 

2. The platform is fixed over the base of the equipment and lies in a horizontal plane. 

3. The test specimen is held firmly over an abrasive paper which is pasted on the upper face of the platform, with the help of two pins holding it at both ends. 

4. The abrading finger has a flat circular rubbing face which is covered with 4 pieces of white abradant fabric during the test. 

5.   The abradant fabric picks up color lost by the test specimen during rubbing. 

6.  It is held over the finger with the help of a tapered ring.

7. Motion to the finger is given through a reciprocating arm with runs and two ball bearings to minimize friction and to apply a uniform load on the finger. 

8. The arm is moved by a manually operated crank and connecting line The equipment is finished in dark metallic paint and bright chrome plating to give it a corrosion-resistant finish.



1. pH meter with the combined electrode.

The front control panel of the pH meter comprises of the following functions:

1) Digital display indicator.

2) Selector switch.

3) Temperature compensate between 0ºC & 100ºC of the solution.

4) Calibrator.

5) Slope.

The rear control is comprised of 

a). Combined electrode input.

b). On-Off switch.

c). The Main fuse.

d). Power cable.

e). Beaker (100 ml)

f). Thermometer

ph meter


a). Standardize the pH meter with different standard buffer solutions by using ‘calibrator’ and ‘slope’knobs.

b). To check the pH of the liquid sample, take the sample in a clean beaker check the temperature of the sample, and set the temperature compensation knob to this value

c). Clean the electrode with distilled water and dry it by means of tissue paper.

d). Dip the combined electrode inside the sample to a depth of about 1 inch and turn the selector switch from stand by’ to ‘pH’ position. The reading shown on the digital display indicator is the pH value of the sample.

e). Put back the selector switch to stand by position, remove the electrode, wash it with distilled water and wipe with tissue paper. When not in use keep it dipped in a beaker containing distilled water.

>Methods for determination of pH of the water

>Buffer solution in chemistry and Types of buffer solution


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