CALIBRATION OF CONDUCTIVITY TRANSMITTER

1.0    PURPOSE:

    To describe a standard operating procedure for calibration of Conductivity transmitter. 
    
2.0    SCOPE:

    The standard operating procedure describes in detail the method for calibration of Conductivity transmitter.
    
3.0    RESPONSIBILITY:

    The responsibility of calibrating Conductivity transmitter lies with the staff of rank not lower than chargeman of maintenance department.

The responsibility of preparation, review and approval of the standard operating procedure lies with the Executive - Maintenance, Manager - Maintenance General Manager (Production) and Head of QAD respectively.
    
4.0    METHOD:

4.1.    Electronic Calibration using a Resistance calibrator and Multi meter: 

4.1.1    Ensure that Multimeter and Resistance calibrator used for the calibration are precalibrated with traceability to national standards. 

4.1.2    For Conductivity range of 0 to 10 μs/cm, install the connections from the Resistance calibrator to Conductivity transmitter.
4.1.3
Disconnect the Conductivity meter sensor wires from the Conductivity transmitter.

4.1.4    Disconnect the indicating meter wires of Conductivity transmitter.

4.1.5    Connect the Multimeter to the Conductivity transmitter to indicate the 4 to 20 mA DC output.

4.1.6    Generate infinite (open) Ω (resistance) from the Resistance generator for ‘zero’ Conductivity.  Adjust span control for a 4 mA DC indication from the multi meter.

4.1.7    Generate 10000 Ω (Resistance) signal from the Resistance generator for 10.00 μs/cm Conductivity.  Adjust span control for a 20 mA DC indication from the multi meter.

4.1.8    Set back the input signal to infinite (open) Ω input resistance, confirm that the multi meter display indicates 4 mA DC output. And also at 10000 Ω input resistance confirm that the multi meter display indicates 20 mA DC output.

4.1.9    Generate and apply the Resistance of 50000 Ω, 20000 Ω, 12500 Ω and 10000 Ω Resistance with the help of calibrated Resistance calibrator to Conductivity transmitter and check the output current in mA DC with the help of calibrated Multimeter.  These are the standard Resistance inputs for the Conductivity ranges 0, 2, 5, 8, and 10 respectively as per the standard chart.

4.1.10    Standard chart for conductivity Vs Input resistance Vs specified output current are mentioned in Annexure-III.

4.1.11    Record the measured output current in mA DC in Annexure-II, against the specified output current in mA DC for the above Conductivity ranges.  Read specified output current in mA DC from the standard chart (Annexure-III). 

4.1.12    Find the difference between specified output current and measured output current record the same as per xxxxx as shown in Annexure-I. 

4.1.13    Acceptance criteria: ± 1.0% of FSD of measured input / output current.

4.1.14    If the input/output current shows difference within the acceptance range, a tag showing the status of the Conductivity transmitter shall be tied to the Conductivity transmitter.

4.1.15    During the calibration, if the Conductivity transmitter does not meet acceptance criteria, service the Conductivity transmitter, recalibrate by informing to the QAD and record the readings as per xxxxx as per shown in Annexure-II.

4.1.16    Even after servicing, if the Conductivity transmitter does not meet the acceptance criteria the Conductivity transmitter shall be replaced with new.  Replacement data shall be recorded in the history card.

4.1.17    Whenever the Conductivity transmitter is rectified or replaced with another, the same shall be informed to QAD.  Recalibration data shall be recorded as per format shown in Annexure-II and also shall be entered in the history card.

4.1.18    Apart from the recalibration, the calibration shall be followed as per the regular schedule.

4.1.19    The Conductivity transmitter which is out of order shall be sent for repairs to outside agency.

4.1.20    Calibration tag for Conductivity transmitter shall be tied to the Conductivity transmitter with the following particulars.

4.1.21    Frequency: Calibration shall be carried out once in six months ± 15 days.
    
5.0    RECORDING:  
                                       
    Recording the details of Conductivity transmitter calibration/recalibration as per Annexure-I and Annexure-II lies with the staff of rank not lower than the Jr.Engineer of maintenance department. 

Conductivity transmitter, engineering, standard operating procedure