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Calibration Dilemmas

 

We are often asked questions about how often should I certify my instrument and why should I ask for an IANZ endorsed certificate – won’t any certificate do from any provider?  

Why IANZ?

If somebody tells you that you do not need to IANZ certify your equipment - do not accept their advice without finding out why or getting a second opinion.
 
Often it’s the companies that cannot provide you with IANZ endorsed calibration certificates that will tell you that you do not need one. Please be wary!
 
If an Inspection body or private quality advisor also tells you that you do not need IANZ – ask them why.
 
An IANZ endorsed certificate ensures the people who test your equipment have had the appropriate training and know what they are doing. Also the reference equipment used to test your instruments is certified and is right for the job. It means the people doing the calibration have been independently audited by technical experts to ensure correct techniques are being used. IANZ 2014 155
 
IANZ is an independent body, free from corruption and is trustworthy – this alone means that NZ calibrations are respected worldwide.
And did you know because IANZ belongs to a mutual recognition arrangement with ilac your IANZ certificates are recognised globally. Ideal for organisations that wish to export.  http://ilac.org/
 
If your instrument is not important to your process do not worry about certification – save your time and money – common sense re importance may prevail here and is discussed later.

How often should I calibrate?

The manufacturer may or may not state the recommended calibration frequency or may even simply state to have them checked regularly
 
The $100 question is what would constitute to be regularly?
 
Because of instances like this IANZ helps us again - we refer to the IANZ Specific Criteria Document/ Appendix 1 & 2 which gives recommendations on frequency intervals. This document provides data that acts as a guideline so that customers can schedule their calibrations.
 
Some Associations and regulatory bodies may state recommended recalibration intervals while others will not. If your regulatory body does not state a required calibration interval – this does not remove any responsibility from you, the end user. It is hoped that in this case that your Inspection bodies are knowledgeable enough to impart best practice and a correct calibration interval is set – if you have doubts ask us to check the IANZ’s specific criteria document for you.
 
Our laboratory certifies 1000s of instruments per year. Instruments can come in looking like new, zeroing fine & still be out of manufacturer’s accuracy specification. Others can come in looking disgusting & actually be fine– unless you check or test your instrument you cannot know if your instrument is working or not.
 
Also some instruments are used twice per year and others twice per day. How often an instrument is used is also a major factor to be considered when determining the calibration interval.

How do I determine if I need an IANZ Certificate?

A good checklist to work out if your instrument requires an IANZ calibration certificate is:
  • The instrument is important to my process
  • It is used to determine that something is safe
  • It is used to check a paying customer’s process
  • You or your customer needs accurate results
  • A regulatory body requires me to have this instrument IANZ certified
  • When you wish to exhibit best practice – e.g. your company is ISO:9001 certified
  • Your process/calibration needs to be recognised internationally
  • When you wish to avoid any rework due to inaccurate testing equipment
  • When you wish to avoid judicial enquiry should something you work on go wrong. 
Calibrate service repair

What is uncertainty?

You will notice an IANZ certificate will provide you with a measurement result, a correction and an uncertainty statement. For added accuracy add the relevant correction to your reading and to calculate how much confidence you can have in your measurements apply the uncertainty value.
 
For example if your reading is 99.5 °C and your correction is +0.5 °C, for added accuracy correct your reading; 99.5 + 0.5 = 100 °C.
 
If your uncertainty value is ±0.1 °C.
Then you can assume 95 % of the time the measurement lies between 99.9 °C and 100.1 °C.
The uncertainty gives the end user confidence in his measurements.

Is IANZ worth it?

Good calibrations may cost a little more but confidence in the results provided enables you to make informed decisions. For example see the case studies below:
 
Pressure:
A production company for an international food corporation was having the instruments on their line calibrated by a non-accredited local lab. 
Staff were unaware of the need for an IANZ calibration. The local lab did not have the expertise to calibrate their equipment correctly and unbeknown to them their instrument was reading 25 % lower than actual.
They were constantly plagued by plant breakdowns. The 12 months following correct calibrations, the plant manager was ecstatic and noted that there had not been one unplanned production stoppage in the preceding 12 months. Previously their equipment had been running under extra stress and nobody knew!
 
Temperature:
Our technicians were called to a cool store when it employed a new supervisor - this cool store had previously been getting their thermocouples checked by an outfit that used the electrical simulation technique – this checked the digital display of their temperature equipment but did not test the actual temperature probes in a live setting.
 
The cold stores temperature controlling equipment was tested using the comparison method utilising IANZ certified reference probes. It was found that the store had been running more than 3 °C colder than what was required. The energy savings alone paid for the calibration in less than four weeks.

Management immediately could see the benefits of having the measurements done, as well as the cost saving, the calibration report they received from our IANZ accredited laboratory became an important marketing tool to show their customer’s that their food was being stored at optimum temperatures.
 
Infrared:
Infrared A salmon producer was confused why one particular supermarket kept rejecting his product as being outside acceptable temperature on arrival. No other customers were having the same issue and the transport company could produce logging details of the temperature of the product during transit.
The salmon producer had the presence of mind to ask the supermarket to certify their testing equipment which was an infrared thermometer (IRT).
 
Our lab tested the IRT and it was well within the manufacturer’s accuracy specification. The lab also sent out an info sheet with the certificate explaining how to use an infrared gun (thermometer).
 
The quality person at the supermarket happened to read the info sheet & decided to observe the next shipment of salmon. It was discovered this particular salmon producer used foil packaging. The low emissivity of the shiny foil caused erroneous readings of the IRT. When the operator was asked to use the IR gun by pointing it into the cavity between packages as the info sheet recommended, immediately the temperature readings complied.
It was a win for the supermarket who learned how to better use their equipment and a win for the salmon producer whose product was now easily within the required temperature requirements.
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