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Why You Should Calibrate Your Materials Tester

Learn why calibration of your materials tester is important, how often it should be calibrated, who can calibrate your materials tester and the price of a calibration.
Why Should Calibrate your Material Tester
By: Toby Rogers, Director of Lloyd Instruments Materials Testing Equipment and Chatillon Force Testing Instruments

You’ve spent a lot of money on a high quality material tester that meets all of your testing needs, and you expect it to last a long time. When you bought it, it was calibrated in the room where it is going to be used so you can be confident the measurements are accurate.

But how accurate are the measurements after a year? After two years? How often should you have your material tester calibrated and who should perform the calibration so that you are guaranteed the best results?

Why is calibration important 
When you have purchased your material tester it will usually be calibrated by a manufacturer accredited Service Technician from the supplier as part of the installation procedure.  After this initial calibration you can be reassured that you have a material tester that is ready for use, that is performing at its best and giving accurate material testing results for your products.

But over time the material tester may become less precise in its measurements due to external influences. Maybe you suddenly notice that you are not getting the test results you expected, or perhaps you never even notice the small inaccuracies in the measurements.  However, the measurements have an impact on your product quality and ultimately your customers may notice a difference in the quality of your products before you find out that something is wrong. This scenario can get very expensive for your company’s finances and for its reputation.

How often should you calibrate your material tester
An accredited calibration certificate is valid for one year, so to ensure that your material tester meets the applicable traceable calibration requirements, and to ensure that your material tester always measures accurately, you should undertake an annual calibration. An annual calibration of your material tester helps to ensure that small inaccuracies that may occur in your material testers measurements are detected before the inaccuracies becomes larger over time and have an impact on the quality of your product, and in some cases the safety of the products.

How is a calibration done
When a material tester is calibrated the reference points of the load cell are checked for accuracy. For this purpose a calibrated set of masses or calibrated load cells covering the load cell range is used. This equipment must be calibrated by an official traceable institute such as UKAS or DANARK. Only when you have performed a traceable calibration can you ensure that the equipment is accurate. For example if the service technician that performs the calibration carries out a calibration of a 100N load cell, he starts by hanging a 10N mass from the mass set onto the load cell. He then read the machine’s display and compares the load reading shown by the material tester with the weight of the mass. This is repeated at 20N, 40N,  60N, 80N and 100N intervals. This is then repeated a further two times to give an average error figure.  If the machine does not show the correct value at any of these points,  the service technician can adjust the value inside the load cell memory so that what is shown on the display matches the actual weight of the mass.

Who can calibrate your material tester
There are several calibration providers for material testers on the market.  Some are independent companies specialized in calibration while others are suppliers and manufacturers of material testers. You should always choose to have your material tester calibrated by the manufacturer of your material tester, rather than a competing manufacturer or an independent company. There are several reasons for this:

Know-how, spare parts and down time
The manufacturer accredited service engineers of your material tester will know your material tester product in detail and have many years of experience, genuine replacement parts and specialist knowledge to provide a complete support solution. If you have your material tester calibrated by your manufacturer, and a part from your material tester need to be changed, the manufacturer will always have the original parts in stock while an independent company may insert a spare part that is not designed for your material tester  and that may cause damage to your material tester, or he will have to order the spare part and you will not be able to use your material tester during the time it takes for the independent company to have the spare part delivered and installed. The independent company may also charge a higher price for the item than direct from the manufacturer.

Specialists in calibration of advanced measuring equipment
As mentioned before it is the manufacturer of your material tester who knows your particular machine in depth. But have you also given any thought that the company you bought the machine from specializes exclusively in material testers of the same type and brand as yours, where as an independent company often deals with calibration of several different types of measurement products? There is a huge difference in the calibration of micrometers and rulers and the calibration of advanced test machines where each machine has a unique calibration setup. 

The price of a calibration
Market prices for calibration are very close and both manufacturers and independent companies offer quantity discounts if you have multiple machines to be calibrated. There is not much difference in the prices of a calibration carried out by an independent company, the manufacturer of your machine and a competing manufacturer of material testers. When choosing the manufacturer of your test machine you will often receive servicing of your machine along with the calibration which, amongst other things, means that safety checks are carried out, belts are tightened, the mechanicals are lubricated and other machine parts are examined for wear. 

It is, however, advisable to make a three year contract for complete preventive maintenance on your material tester as this kind of contract will offer you a reduced price on calibration, service and support without compromising the quality.