SOP For calibration of conductivity meter is described in this post which you can follow in the section of the General Industry SOP.

OBJECTIVE

To calibrate the equipment for reliable & accurate results.

SCOPE

This procedure is applicable to calibrate the conductivity TDS meter, installed in Q.C. dept.

RESPONSIBILITY

QC Analyst

ACCOUNTABILITY

Manager Quality Control

PROCEDURE

  • Connect a conductivity cell of 0.1K & temp. probe to the cell socket if not connected.
  • Press the ‘CAL’ key.
  • Display will show Std Y n, asking whether standardization is to be done yes (y) or not (n).
  • Then again press the ‘CAL’ key.
  • Display will show ‘put std’.
  • Stroke the ‘PUT STD’ key until 0.01 M KCL solution indicated by the LED lamp.
  • Immerse both probes in the 0.01 M KCL std solution.
  • Press ‘CAL’ key.
  • The unit starts calibrating itself against the standard solution, the display in between blinks with ‘CAL’.
  • After 20 second the measured value of the cell constant will be displayed as (x.xx CEL.C) for a short time, where x.xx is a measured value of cell constant.
  • Thereafter the display will ask ‘PUT SOLU’.
  • In case when the display shows ‘str data’ & cell constant with concentration of previously calibrating solution, press ‘CAL’ key. Or in case display shows, conductivity value or TDS value, press “ABORT NO” key. Then press ‘CAL’ key.
  • Press ‘COND’ key.
  • The unit will display busy and after a while, it will show the temp. correlation factor (1.9 t) along with the conductivity of the standard KC1 solution at 25°C. Record the observation in the format as per Annexure.
  • Simultaneously check the TDS of std KC1 solution.
  • Press “ABORT No” key. The display will show “PUT SOLU”.
  • Then press “TDS-F TEMPCO” key. The display will show (x.xt x.xxt). Where xxt. is temp correlation factor & x.xx is TDS factor.
  • For 25°C Tempco correction is 1.9 & TDS factor 0.53 is for 0.01 m KCl std. solution & 0.51 is for 0.001 m KCl std solu.
  • Enter temp. correction factor & TDS factor as per SOP.
  • Then press “TDS” key, the display will show busy. After a while, it will show the actual temp. and TDS value in PPM/PPT.
  • Remove conductivity cell & temp probe from the std 0.01 M KCl solution.
  • Rinse it with purified water.
  • Press ‘ABORT NO’ key, the display will show put solu.
  • Immerse both cell & temp probe in 0.001 M KC1 std solution.
  • Then again press ‘CAL’ key the display will show put std.
  • Stroke the ‘PUT-STD’ key unit 0.001 M KCl solution indicated by the LED lamp.
  • Press ‘CAL’ key.
  • Rinse it with purified water.
  • Keep the cell immersed in purified water in between and after the measurement.
  • This instrument is now ready to measure the conductivity & TDS of an unknown sample.
  • Conductivity & TDS limit of std. KCl solution at 25°C is below
  • If the value is out of limit then follow the SOP.
  • Check the electronic circuits once in a month with a standard resistor (1 MΩ)
  • Check the resistor accuracy with multimeter once in a month. If the register is 1 MΩ, potency, the multimeter will show 1 MΩ + 5%.
  • Clean the instrument with the dry clean cloth.
  • If the conductivity cell and temperature probe are connected with the instrument, disconnect it and connect –1 MΩ (i.e. 1 µS) resistor.
  • Switch ‘ON’ the instrument.
  • After about 3 seconds, if the instrument has been calibrated previously, the display will show ‘Str data’ and cell constant with previous calibrating solution concentration, alternatively.
  • Press ‘CAL’ key, the unit display will show ‘PUT Std’ then press “put std” key seven times and the display will show ‘res’.
  • Press ‘COND’ key display will show ‘busy’.
  • Carry out ‘Tempco correction’ for 25°C.
  • After few second, display will show the value of the resistor in µs if the resistor potency 1 MΩ, the display will show value as temp in °C along with 1.0 µs + 5%.

Frequency: Once in a month.