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SOP for Calibration of Conductivity Meter


Standard operating procedure to calibrate the conductivity meter by KCl solution.

1.0  OBJECTIVE

       To calibrate the equipment for reliable and accurate results.

2.0  SCOPE

       This procedure is applicable to calibrate the conductivity meter.

3.0  RESPONSIBILITY 

3.1  Doing      : Technical Assistant
3.2  Checking : Executive /Manager

4.0  ACCOUNTABILITY

       Head of the Department

5.0  PROCEDURE

5.1  Connect a Conductivity Cell of  0.1 K value to the CELL  socket.
5.2  Operate the instrument as per S.O.P.
5.3  After about 3 seconds of switching on the instrument the display will show ‘Put Std ‘
5.4  Dip the conductivity cell and temperature probe in 0.001 M Std. KCl solution.
5.5  Stroke the Std SOL key until 0.001M  KCl solution indicated by the LED lamp .
5.6  Press CAL key.5.7 The unit starts calibrating itself against the standard solution. The display in between  blinks with Sys  busy.
5.8  After about 10 second the measured value of the cell constant will be displayed as (X.XX CEL.C) for  a short time. Where X.XX is measured value of cell constant .
5.9  Thereafter the,display will ask Put SOLU
5.10  In case when the display shows Str Data & cell constant with concentration of previously calibrating  solution, Press CAL key.
5.11  The display will show Std  y n, asking whether standardization is to be done ( Y ) or not ( N ).
5.12  Again press CAL key, the display will show Put Std and put std. solution  of 0.001M KCl.
5.13  With the cell and temperature probe already immersed in  the standard  solution of 0.001M  KCl 
press CAL key again. 
5.14  The unit starts calibrating itself against the standard solution. The display in between blinks with SYS  busy.
5.15  After about 10 seconds the measured value of the cell constant will be displayed as (X.XX CEL.C) for a short time.Where X.XX is measured value of cell constant  .
5.16  Thereafter the display will ask Put SOLU .
5.17  Carry out  TEMPCO correction as per S.O.P.
5.18  Press COND key.
5.19  The unit will display Sys busy and after a while, it will show the actual temp. along with the conductivity of the standard KCl solution at 25oC. Record the observation in the format as per annexure.
5.20  The Conductivity of 0.001 M KCl  solution at 25oC should be 0.146 mS/cm .+/- 0.005 .
5.21  Remove the conductivity cell and temperature probe from standard  0.001 M KCl solution 5.23      Rinse with distilled water .
5.24  Press CAL key, the display will show Std Y n.
5.25  Again  press CAL key, the display will show Put Std.
5.26  Stroke the STD SOL Key until the 0.01 M KCl solution indicated by LED lamp .    
5.27  Press CAL key.
5.28  The unit ‘Starts’calibrating its self against the standard solution. The display in between blink with SYS  Busy.
5.29  After about 10 seconds, the measured value of the cell constant will be displayed as (X.XX CEL.C) for a short time, where X.XX is measured value of cell constant.   
5.30  There after the display will ask about Put SOLU.
5.31  Carry out TempCo correction as per S.O.P.
5.32  Press COND key.
5.33  The unit will display Sys Busy and after a while, it will show the actual Temp. along with the conductivity of the standard KCl solution at 25oC. Record the observation in the format as per Annexure,
5.34  The Conductivity of 0.01 M KCl  solution at 25oC should be 1.41 mS/cm .+/-  0.01.
5.35  The instrument is now ready to measure the conductivity of unknown solution.
5.36  Remove the conductivity cell and temperature probe from the standard solution .
5.37  Rinse it with distilled water.
5.38  Keep the cell immersed in distilled water in between and after the measurement.

5.39  Frequency of calibration : Daily

5.40  Calibration of conductivity meter with Standard RESISTOR
5.40.1  The basic working accuracy of the electronic circuits of the instrument can be checked with the help of Standard RESISTOR (1 M W ).
5.40.2  Check the Resistor accuracy with Multi Meter every month. If the Resistor is of 1 M W, potency Multi meter will show 1 M W (± 5%).
5.40.3  Clean the instrument with dry clean cloth.
5.40.4  If the conductivity cell is connected with instrument, disconnect it and connect 1 M W (ie. 1mS) resistor along with temperature probe.
5.40.5   Switch ‘ON’ the mains.
5.40.6   Switch ‘ON’ the instrument.
5.40.7  After about 3 seconds, If the instrument has been calibrated previously, display will show ‘Str data’ and cell constant with previous calibrating solution concentration, alternatively.
5.40.8  Press CAL Key until display will show PUT STD, then press STD SOL Key seven times and display will show ‘rES’.
5.40.9  Press COND Key, display will show  ‘SYS busy’.
5.40.10  After few second ,display will show the value of Resistor in mS. If the Resistor potency 1 M W, display will show value as temperature in oC along with 1.0mS ± 5 %.
5.40.11 If the value is out of limit, inform the service engineer to repair the instrument.

5.40.12  Frequency of calibration  = Daily

6.0  ABBREVIATIONS

6.1  M= Molar
6.2  oC= Degree centigrade
6.3  ms/cm= milisimens per centimeter  
6.3  %= Percentage
6.5  M W= Mega Ohms
6.6  ┬Ás= Micro simens



ANNEXURE
Q.C. DEPARTMENT
INSTRUMENT CALIBRATION RECORD                   
NAME OF THE INSTRUMENT  :  CONDUCTIVITY METER
MAKE                                           :   SYSTRONICS
MODEL No.                                  :   306
IDENTIFICATION No.                :
Preparation of Standard KCl Solution: 7.456gm --> 1000ml with Distilled water (0.1M) (Sol. A )                                  
                                    25ml Solution-A --> 250ml with Distilled water (0.01M) (Sol. B)
                                    25ml Solution-B --> 250ml with Distilled water (0.001M)
                                    Conductivity of Std. KCl at 25°C , 0.01M =   1.41ms/cm
                                    Conductivity of Std  KCl at 25°C  0.001M = 0.146ms/cm   
Resistor accuracy checked with multimeters  =_____ MW   Date  :______ Sign.:_________


Date
Conductivity at 25°C ms/cm
Value of  1M W Resistor
1.0 mS ± 5%
Cell
Constant
0.1+/- 10%
Sign
0.01M KCl
1.41 ± 0.01
0.001M KCl
0.146 ± 0.005


























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