SOP for Operation, cleaning and calibration of microprocessor colony counter

1.0       OBJECTIVE

To lay down a standard procedure for operation, cleaning and calibration of microprocessor colony counter to ensure the rapid and accurate counting of microbial colonies (CFU).

2.0       SCOPE

This Standard Operating Procedure is applicable for counting of microbial colonies (cfu) from petri plates.


            Microbiologist shall be responsible to follow the procedure mention in this SOP.


Department Head & QA Head shall be accountable for effective implementation of this SOP.


Format for daily calibration record of Microprocessor colony counter       – Attachment-I

6.0       PROCEDURE

6.1           Operation of colony counter

6.1.1        Connect the power cord of the colony counter to power supply and switch ‘ON’ the main switch.

6.1.2        Turn ‘ON’ the instrument by pressing the ON/OFF switch.

6.1.3        Press the ‘RESET’ button. The display will show 0000.Place the desired plate on the glass grid.

6.1.4        Remove the cap of the marker and press firmly keeping the pen straight/vertical, on the petri plate

where  a microbial colony is located.

6.1.5        The colony counter will register a count, there will be a beep sound and an ink dot will be marked on

the petri  plate. Continue till all the colonies are thus counted

6.1.6        When all the colonies are counted, note down the final reading from the counter.

6.1.7        For next counting press the ‘RESET’ button for starting the counting with zero.

6.1.8        Maintain the microprocessor colony counter usage record in logbook of colony counter.

6.1.8        Switch ‘OFF’ the power switch of colony counter.

6.1.9        After completion of work clean the colony counter with 70% IPA with lint free duster.

6.2           Cleaning of Colony counter

6.2.1        De-dust the external surface of colony counter and magnifier with a lint free duster.

6.2.2        Clean the external surface of colony counter with wet duster soaked in 70% I.P.A. solution.

6.3           Calibration of Colony counter

6.3.1        Connect the colony counter to the main supply and switch ‘ON’ the power switch.

6.3.2        Now operate the colony counter as per step 6.1.

6.3.3        Place an empty petri plate on the glass grid.

6.3.4        Press the tip of marker pen 5 times till audio buzzer indicates beep sound and then check the number

displayed on the screen, it should be 0005.

6.3.5        Press the ‘RESET’ button, the digital display will show “0000” again press the marker pen 10 times

on  the surface of petri plate.

6.3.6        Repeat the same procedure by pressing the marker pen 15 times, 20 times and 25 times.

6.3.7        Calibration of colony counter is valid if the number displayed on the screen is equal to the number of

times of marker pen pressed.

6.3.8        After completion of work, press the reset button, switch ‘OFF’ the mains.

6.3.9        Maintain the record of daily calibration of microprocessor colony counter in attachment-II.

7.0       REFERENCES



SOP: Standard operating procedure

IPA  : Isopropyl Alcohol

CFU  : Colony forming unit

QA    : Quality Assurance

QC    : Quality Control


Quality Assurance Department

Quality Control Department



Version Number Effective Date Reason for Revision


Format for daily calibration record of Microprocessor colony counter       – Attachment-I

S. no. Date          No. of press shown on digital display Done by Checked by Remarks
5 times 10 times 15 times 20 times 25 times












Microbiology Labs Documents