Universal Testing Machine Calibrations: What, Why, and How

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universal testing machine calibrations performed by ADMET technician

An ADMET engineer calibrates a universal testing machine

Calibration of a universal testing machine entails verification of the accuracy of the system’s instruments responsible for obtaining force and displacement measurements.  In principle, calibration of an instrument is the comparison of the instrument to one that has been calibrated to a known traceable standard. This ultimately certifies its accuracy and determines traceability of the measurements.  Internationally recognized standards have been developed for calibration of crosshead speed and displacement (ASTM E2658 and E2309), strain and load rate (ASTM E2309), and measurement of tension, compression (ASTM E4), torque (ASTM E2624), and dynamic force (ASTM E467). Calibration certificates typically display a range of reference values generated by the calibration device, the corresponding values obtained by the instrument being calibrated, and the difference between the two. If the instrument being calibrated is not within a specified tolerance, it is adjusted to be within bounds of the specification if possible. Otherwise, further investigation may be required to determine the cause.

ADMET offers a variety of calibration and maintenance services for both ADMET systems and those made by other manufacturers including MTS, Shimadzu, Tinius Olsen, retrofitted Instron®, and SATEC®.

Why should I calibrate my system?

In general, the goal of calibration of a universal testing machine is to minimize uncertainties in test results by ensuring the accuracy of the measurement devices.

Many companies use universal testing machines to validate their product’s material properties during their quality control stage prior to distribution. Often times, the product’s test results must fall within a range of values in order to the product to “pass”. Performing these validation tests with a system whose calibration certifications have expired may yield inaccurate test results, which may ultimately lead to a company distributing non-conforming products. In order to reduce the potential of manufacturing errors within a company, maintaining an up-to-date calibration schedule is vital. In research and development laboratories, inaccurate test results may lead a user to inaccurate conclusions about a test specimen, distorting proposed findings. Testing laboratories must maintain certification through calibration to ensure that they can dependably perform requested tests by their customers. In most settings where universal testing machines are used, it is fundamental that the measurement devices associated with the machine be as accurate as possible. For this reason alone it is important, and for some companies essential, to maintain a consistent and frequent calibration schedule.

How often should I calibrate my system?

Accredited calibration certificates typically expire after one year. In order to ensure that your materials testing system is providing accurate and precise measurements, ADMET recommends measurement devices incorporated into a materials testing system be calibrated annually, at the minimum. Users should review their calibration certificates annually to see if any devices have deviated significantly in terms of accuracy. This mitigates the risk of producing invalid results.

In addition to regular scheduled calibration, many ASTM and ISO standards, such as ASTM E4, require that a system be re-calibrated after a move.  Furthermore, certain industries may be subject to additional regulations which require more frequent calibrations.

How is calibration performed?

technician performing universal testing machine calibrationsADMET technicians use our Gauge Buster 2 Portable Calibration unit to calibrate measurement devices on a materials testing machine. When a materials testing machine is calibrated, reference points of the measurement device are checked in comparison to a device calibrated to a known traceable standard laboratory, such as NIST. The calibration procedures are determined by internationally recognized standards. For example, ASTM E4 specifies tension and compression force calibration procedures.  The locations of the reference points to be calibrated are determined by the standard and checked on an initial run. The verification is then repeated a second time. If the error on each run and the repeatability calculations show error less than 1%, the measurement device passes and calibration is verified. If the errors are greater than 1%, the service technician will adjust values of the measurement device’s calibration manually so that the measurements match the target range of the calibrated device.

Who should I contact to calibrate my system?

If you’re interested in learning more about calibration, or would like to be quoted for the calibration of your universal testing system, please reach out to one of our sales engineers, or fill out our Calibration Request Form. Our sales engineers work directly with customers to properly determine components of their system’s calibration, and also with our scheduling department to provide our customers with quick and convenient calibration dates.

For more information, visit our Calibration Services page.

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By |October 25th, 2017|Testing Issues|Comments Off on Universal Testing Machine Calibrations: What, Why, and How