NUMBERING AND CALIBRATION OF SENSORS PROBES FOR DIGITAL TEMPERATURE INDICATORS CONTROLLERS

1.0 PURPOSE:
    
To describe a standard operating procedure for Numbering and calibration of Sensors/Probes for digital temperature indicators / controllers. 
    
2.0    SCOPE:
    
    The standard operating procedure describes in detail the method for Numbering and calibration of Sensors/Probes for digital temperature indicators / controllers. 
    
3.0    RESPONSIBILITY:
    
    The responsibility of calibrating sensors/probes for digital temperature indicators/ controllers lies with the staff of rank not lower than supervisor of maintenance department.

The responsibility of preparing, reviewing and approving the standard operating procedure lies with the Manager-Maintenance, Head of Production and Head of QAD respectively.
    
4.0    METHOD:
    
4.1    Identification numbers of sensors/probes for Digital temperature Indicators/ Controllers shall be given as Identification number of the Digital temperature Indicators/ Controllers followed as an alphabetical suffix, i.e.; A,B,...  depends on the number of sensors/probes connected to the indicator/controller.

4.2    Identification No. shall be marked on the sensor.

4.3    Select a standard multimeter to measure resistance of the under test sensor/probe and a standard digital temperature indicator with sensor/probe to measure the temperature of Hot/Cold bath, which are calibrated to the traceability with the national physical laboratory OR their authorized agency.

4.4    Take a hot bath and heat to the temperature nearer to the maximum operating/calibration range of the sensor/probe. Dip the standard sensor/probe and the sensor/probe which has to be calibrated in hot bath.

4.5    Check the resistance of the under test sensor/probe at various temperatures i.e. from 50°C to 200°C and record the readings in Annexure-I.

4.6    Check the standard resistance at various temperatures (where the under test sensor/probe is checked) i.e. 50°C to 200°C using Resistance vs Temperature chart (which is enclosed in Annexure-III) and record the same in Annexure-I.

4.7    Similarly take a chilled bath and cool to the minimum operating/calibration temperature of the sensor/probe. Dip the standard sensor and the sensor/probe which has to be calibrated in chilled bath.

4.8    Check the resistance of the under test sensor/probe at various temperatures i.e.
-10°C to 0° and record the readings in Annexure-I.

4.9    Check the standard resistance at various temperatures (where the under test sensor/probe is checked) i.e. -10°C to 0°C using Resistance vs Temperature chart (which is enclose in Annexure-III) and record the same in Annexure-I.

4.10    Compare the readings of the resistance measured with standard resistance (Recorded from standard chart). Find the difference and record the same in Annexure-I.

4.11    Acceptance criteria: + 0.5% of the FSD ( Full Scale Division).

4.12    If the difference is beyond the acceptance criteria replace the sensor with new and then inform to the QAD and same shall be recorded in the history card of the respective digital temperature indicator/controller.  

    
    
4.13    Whenever the complaint received from user department that the sensor/probe not working, check the connecting cables of the sensor/probe for intactness and recalibrate the same.

4.14    Recalibration data, shall be recorded in the formant MT/F069 shown in Annexure-II.

4.15    Apart from the recalibration of instruments, the calibration shall be followed as per regular schedule for all the sensors/probes.

4.16    Whenever sensor/probe rectified/replaced with new/recalibrated, inform to the QAD and same shall be recorded in the history card of the respective digital temperature indicator/controller.  

4.17    Calibration tag shall be tied to the sensor with the following particulars.

4.18    Standard resistance vs temperature chart is enclosed in Annexure-III.

4.19    Master list of sensors/probes shall be prepared as per Annexure-IV.

    
    
4.20    A schedule shall be prepared for the calibration of sensors / probes as per 
Annexure-V.
    
4.21    Calibration of sensors/probes shall be carried out by outside agency traceability to national standards in presence of maintenance department as per the procedure. Recalibration shall be carried out by maintenance department.

4.22    Frequency: 

Calibration of sensors/probes for digital temperature indicator/controller shall be carried out once in three months ± 2 days.
    
5.0    RECORDING: 
        
The responsibility of recording the results in the Annexure-I and History Card lies with staff of rank not lower than the supervisor. 

Engineering, standard operating procedure, numbering and calibration of sensors