| Operation and Calibration of pH and Conductivity meter (Labman) |
1.0 OBJECTIVE To lay down a procedure for operation and calibration of pH and Conductivity meter (Labman) used in quality control. 2.0 SCOPE This procedure is applicable for operation and calibration of pH and Conductivity meter used in quality control lab. 3.0 RESPONSIBILITY QC-Officer/ Sr. Officer / Executive and above. 4.0 ACCOUNTABILITY Head-QC 5.0 PROCEDURE 5.1 Operating Instruction: 5.1.1 Instrument consist six keys and the function of each key is as follows: 5.1.1.1 MEAS: Power the meter ON/OFF. The measured value on the display, press the key again to resume measuring in pH meter. In the calibration and temperature setting mode, exists current mode and return to measurement. 5.1.1.2 MODE: Toggle between pH and mV measurement mode. CAL: Press the key to enter the calibration mode. 5.1.1.3 Press and hold the key to enter the setup menu 5.1.1.4 °C: Press the key to set the temperature or enter the temperature calibration mode. 5.1.1.5 ↑: Press the key to increase setting value. 5.1.1.6 ↓: Press the key to decrease setting value. 5.1.1.7 ENTER: Confirm the calibration, setting value or displayed option. 5.1.2 Before switch on the pH and Conductivity meter pre-check the cleanliness and power plug is properly connected to mains. 5.1.3 To start the pH and Conductivity meter press the ‘ON/OFF’ switch for power supply to the instrument and the screen will display. 5.1.4 Press MEAS key to turn on the meter. 5.1.5 Press and hold the MEAS key for 3 seconds, the meter will turn off. 5.1.6 If do not press any key for 3 hours, the meter will turn off automatically. 5.2 Calibration of pH and Conductivity meter: 5.2.1 pH meter: 5.2.1.1 pH meter allows up to 5 points the calibration in the pH mode. 5.2.1.2 The meter will be automatically recognizing and calibrate to following standard buffer solutions NIST Standard Buffer solutions: pH 1.68, pH4.01, pH 6.86, pH9.18, pH12.45 USA Standard Buffer solutions: pH 1.68, pH 4.01, pH7.00, pH10.01, pH12.45 5.2.1.3 Before starting the calibration select the 5-point calibration in the set up menu. 5.2.1.4 Rinse the electrode with purified water. 5.2.1.5 Press CAL key, the meter shows “CAL 1/pH 1.68. 5.2.1.6 Dip the electrode in the standard buffer solution (1.68pH). Stir the sensor gently. 5.2.1.7 Press the enter key to confirm. Wait the measure value to stabilize, the display shows “END” in pH meter. 5.2.1.8 When the first calibration point is done, the display will show “CAL 2/pH 4.01”. 5.2.1.9 When the second calibration point is done, the display will show “CAL 3/pH 6.86” or 7.00. 5.2.1.10 When the third calibration point is done, the display will show “CAL 4/pH 9.18” or 10.01. 5.2.1.11 When the fourth calibration point is done, the display will show “CAL 5/pH 12.45”. 5.2.1.12 Rinse the electrode with purified water and dip the pH electrode in to the standard buffer solution (pH 12.45). Stir the sensor gently. 5.2.1.13 Press enter key to confirm. Wait for the measured value to stabilized, the display showed the electrode slope and “CAL 5/pH 12.45 in pH meter. 5.2.1.14 Press enter key to confirm. Wait for the measured value to stabilized, the display showed the Electrode slope and “END” in pH meter. 5.2.1.15 pH meter calibration should be recorded in Daily Calibration Record for pH Meter format no. QC01-005/F01. 5.2.1.16 The meter automatically returns to measurement mode. Calibration is completed. 5.2.1.17 After measuring the reading pH electrode dip in Saturated Potassium chloride. 5.2.1.18 During the calibration, if the meter shows the “ERR”, check the pH electrode and Calibration Solutions are fresh and uncontaminated. 5.2.1.19 If their requirements of exit from calibration press MEAS key the meter will Immediately return to measurement mode. 5.2.2 Conductivity meter: 5.2.2.1 Switch on the mains and see that the screen displays “LABMAN pH / Cond. meter”. 5.2.2.2 Conductivity meter allow up to 3 points calibration in the conductivity mode. 5.2.2.3 Before starting the calibration select the 3-point calibration and cell constant in the set up menu. 5.2.2.4 The meter will be automatically recognizing and calibrate to following standard buffer solutions Standard Buffer solutions: Conductivity (84µS/cm, 1413µS/cm, 12.88mS/cm) 5.2.2.5 Rinse the electrode with purified water. 5.2.2.6 Press CAL key, the meter shows “CAL 1/Cond.84µS/cm 5.2.2.7 Dip the electrode in the standard buffer solution (84µS/cm). 5.2.2.8 When the first calibration point is done, the display will show “CAL 2/1413µS/cm”. 5.2.2.9 When the second calibration point is done, the display will show “CAL 3/12.88mS/cm”. 5.2.2.10 Press enter key to confirm. Wait for the measured value to stabilize, the display will show “END” in pH meter. 5.2.2.11 The meter automatically returns to measurement mode. Calibration is completed. 5.2.2.12 Conductivity meter calibration should be recorded in Daily Calibration Record for conductivity Meter format no. XXX. 5.2.2.13 pH meter and conductivity meter operation record should be recorded in instrument usage log book format no. XXX. 5.3 CALIBRATION (NIST Traceable solution to be used for the calibration purpose) 5.3.1.1 Switch ON the mains and see that the screen displays “LABMAN pH / Con meter”. 5.3.1.2 Allow the instrument to stabilize for at least 30 minutes before performing Daily calibration. 5.3.1.3 Rinse the conductivity electrode and temperature probe with Purified water, remove the excess water by soaking with tissue paper and insert the electrode and temperature probe in calibration standard solution 84µS/cm. 5.3.1.4 Press “MODE” key which displays 1) pH, 2) Cond. Press “2” and Press “ENTER” key which displays “Conductivity Mode”. Press “2” 5.3.1.5 Press “MODE” key which displays “Conductivity Mode”. Press “ENTER” key which displays “Enter Cell Const.” 5.3.1.6 Enter the cell constant value as mentioned on electrode and press enter so screen displays “Calibration 1) Y 2) N” 5.3.1.7 Note: Use the electrode having cell constant value 0.096±4 %( 0.092 to 0.100). 5.3.1.8 Cond. = xx.x mS. Press Enter after reading is stable. 5.3.1.9 After that screen display “Cond = xx.x mS *No. x C 5.3.1.10 K = n.xyzxx.x °C * Sample Reading No. eg. R1 5.3.1.11 Display show the cell constant against the standard used. The obtained cell constant shall be within 80% – 120% limit of the specified cell constant, record the result 5.3.1.12 Verify and note down the reading of calibration standard solution of 84 µS/cm at approximately 25.0±2 °C and record mentioned as per Format No. QC01-005/F02 (Daily calibration record for conductivity meter) obtained value should be within ±5% of standard value. 5.3.1.13 If the obtained cell constant is within limit then remove the calibration standard solution and rinse the conductivity electrode and temperature probe with purified water, remove excess water by soaking with tissue paper and keep it in air. Now instrument is ready for sample measurement. 5.3.1.14 If the obtained cell constant is out of limit then the screen displayed “Incorrect Buffer or Probe Faulty” means calibration does not meet the requirements. Re-calibrate the instrument using fresh calibration standard solution and if display shows again as “Probe faulty” then the electrode should be disposed of and another electrode should be used and calibrate the instrument. 5.3.1.15 TDS Factor: Set the TDS conversion factor for TDS measurement. |