Clause 7.6 Control of monitoring and measuring equipment

Verifications, inspections and tests are important ways to ensure that the product meets the customer's expectations. This can be done by monitoring and measuring the characteristics of the product (see 8.2.4).

For example, a pharmacist measures the exact amount and weight of the medicine before providing it to the customer. However, if his measuring device (an electronic scale) is measuring incorrectly, or if it is not accurate enough, then the measurement is useless.

Therefore, this section of ISO 9001 requires organizations to ensure that measurement devices are controlled so that they measure correctly.

Example, of measurements and monitoring devices are: scales, gages, thermometers, micrometers, callipers, and thickness meters.

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  They should be calibrated periodically. Calibration is the act of comparing the measurement device against a reference standard to determine how accurate it is and whether or not it is still capable of meeting the precision required for the measurement made with it. Where necessary, the measuring device needs to be adjusted.


• Organizations are free in determining the frequency of calibration, provided that the frequency is consistent with the type of measurement device and intensity of use.


• For a reference standard to have validity, it must be traceable back to an appropriate recognized accurate source. This is normally a national or international standard (such as a meter or a kilogram). If an international or national standard does not exist, then the organization needs to define the reference standard on its own.


• It is important to determine how accurate the measurements need to be. This will depend upon how much tolerance is permissible in what is being measured. A measuring device usually has to be capable of measuring to a much closer tolerance than the tolerance specified for the item being measured. Also, there is no point in having measurement devices calibrated to unnecessarily high precision if that precision is not needed for the operation. A pharmacist typically needs high accuracy equipment, while the accuracy of a wire cutter used by a distributor is relatively low.


• The results of the calibrations need to be recorded. If the measuring device appears to be out of calibration, then it is necessary to look at the results of the measurements that were previously taken with this device. For example, if a scale is out of calibration, someone may need to re-inspect the product that was recently inspected with this device (provided the product has not yet been shipped to the customer). Organizations need to decide which corrective action is appropriate (see 8.5.2).


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  It is important to protect a measuring device from damage or deterioration. This means that it must be suitably stored when not in use, and it must be correctly handled. Also, adjustments may invalidate the calibration; a possible prevention method is to ensure that only trained personnel is authorized to use the measuring device.
  Sometimes computer software is used in the process of monitoring and measurement of requirements. If this is the case, then the software must be checked if it performed the required function. Where calibration of device is not possible or practically feasible than verification should be done to fulfil the requirement of this standard.

In 2008 edition, term "device" is replaced by "equipment". A small appropriate change to make the term suitable for a wider range of industry segment.

A note at the end of clause is added stating that confirmation of the ability of computer software to satisfy the intended application would typically include its verification and configuration management to maintain its suitability for use as computer software is now being extensively used for quality assurance purposes in all types of industry and hence clarity was needed.

Guidance for Educational Institutions:

A school or college developing question paper for examination also falls under the category of monitoring and measuring equipment because it is used to measure the competence level of examinee.
Control of (or Calibration of) question paper will be consisting of setting guidelines for preparation of question paper so that entire syllabus is covered and then reviewing it to verify that question paper meets the set guidelines before releasing.

Guidance for Software Companies:

Software testing tools and scripts developed to run on these tools will fall under the category of monitoring and measuring equipment.
To meet the requirement of the standard, verification of scripts prior to testing will be needed.
ISO 9000 defines verification as Confirmation, through the provision of objective evidence, that the specified requirements have been fulfilled.

Guidance for engineering companies:

1. 
   
   Identify the measurements and measuring limits.
   The measuring limit is a range under which product is acceptable.
   These limits may be defined as % of value or as a fixed tolerance, either one sided or both sided e.g.:
   Length = 50 mm + 1 mm (Both sided fixed tolerance in absolute value) or
   Length = 50 mm + 2 % (Both sided fixed tolerance in % of value) or
   Length = 50 mm + 1 mm (One sided fixed tolerance) or
   Length = 50 mm (+ 1 mm, -0.5 mm), (Both sided fixed tolerance of different value) etc.


2. 
   
   Select appropriate measuring devices and define control limits.
   Selection of equipment should be based on importance of parameter in achieving conformity i.e. accuracy needed.
   Following parameters should be considered while selecting measuring and monitoring device:
   1. Range of measurement, required.
   2. Least count
   3. Accuracy
   4. Repeatability
   5. Reproducibility
   1. Range of measurement:
   Minimum and Maximum limit of values required to be measured.
   2. Least count:
   Minimum value that can be measured with the device with defined level of confidence and accuracy.
   3. Accuracy:
   Closeness of the measured value to actual.
   4. Repeatability:
   Accuracy of measurement achieved when measurements are carried out by one person under defined circumstance.
   5. Reproducibility:
   Accuracy of measurement achieved when measurements are carried out by different persons under defined circumstances.
   For all practical purposes we will consider "accuracy" means maximum of accuracy, repeatability and reproducibility.
   Example:
   Say measurement requirement is:
   Length = 50 mm + 1 mm
   If you select measuring device as vernier having least count of 0.01 mm and accuracy of 0.02 mm. The control limits will than be:
   Length = 49.02 to 50.98 mm
   Because the values 49.00 to 49.02 and 50.98 to 51.00 are suspect zone, i.e. the values in this range might be lower than 49 or higher than 51 respectively because of the accuracy of the instrument is 0.2 mm. As a thumb rule accuracy of device should be at least 1/3 of measurement accuracy. A 1/4 or 1/5 is considered a better option.


3. 
   
   Calibrate the measuring devices periodically, as appropriate
   This periodicity may be prior to use, daily, weekly, monthly, bimonthly, six monthly, yearly or even more.
   The frequency of calibration will depend upon type of device and severity of use.
   In some cases, where high level of measurement accuracy, the devices are calibrated prior to and after taking the measurement and if difference is observed in two calibrations than either measured value is corrected accordingly or even provision is made to repeat the measurement.


4. 
   
   Reference standards
   Calibration should be traceable to national or international standards, if such standards exist. In cases, where national or international standard do not exist, than basis used for calibration should be recorded.
   In 1994 edition, the standard required "basis used for calibration should be documented", which was interpreted as documenting the procedure or work instruction for calibration of that device.
   Recording the basis of calibration on the calibration certificate should be considered as enough evidence of conformity to the requirement of 2000 edition of the standard.
   Traceability to National / International standard is maintained as follows:
   Level - I: Device in National/ International Physical Laboratory, it is a representative sample with highest possible accuracy. Level - II: Device in National Physical Laboratory used for calibration for tertiary devices.
   Level - III : Device calibrated using second level device and used for calibration of devices used for measurement and monitoring in day to day activities in production and quality assurance. This device is often called "Master" or tertiary instrument (devices).
   Level - IV: Device used for measurement and monitoring in day to day activities in production and quality assurance.
   The calibration certificate of device "under calibration" should identify the "Master" used for calibration and its accuracy.
   The calibration certificate of device used as "Master" should identify the National Physical laboratory (NPL) device used and its accuracy.

External Document Reference: Documentation Kit

Standard Operating Procedure for Control of Measuring and Monitoring Equipments

List of Monitoring & Measurement equipment

Calibration Report / Certificate

Additional Key words: calibration, calibrate, instrument, inspection