Calibration of a universal testing machine involves validation of the accuracy of the system’s instruments responsible for achieving displacement and force measurements. Technically speaking, calibration of an instrument means comparing the instrument to one that has already been calibrated to an accepted traceable standard.
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Image Credit: Admet Inc.
Ultimately, this certifies the accuracy of instruments and determines traceability of the measurements. Internationally recognized standards have been created for calibration of strain and load rate (ASTM E2309), speed and displacement (ASTM E2658 and E2309), and measurement of dynamic force (ASTM E467), torque (ASTM E2624), tension and compression (ASTM E4).
Calibration certificates typically display different reference values produced by the calibration device, the corresponding values achieved by the instrument that is being calibrated, and the difference between the two. If the instrument that is being calibrated is not within a particular tolerance, it is modified to be within the specification bounds if possible. Otherwise, additional investigation may be needed to determine the cause.
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An ADMET engineer calibrates a universal testing machine. Image Credit: Admet Inc.
ADMET provides a wide range of calibration and maintenance services for ADMET systems as well as those developed by other manufacturers including SATEC®, retrofitted Instron®, Tinius Olsen, Shimadzu and MTS.
Why Should A System be Calibrated?
Generally, the aim of calibration of a universal testing machine is to reduce uncertainties in test results by ensuring the accuracy of the measurement devices. Universal testing machines have been used by many companies to validate the material properties of their product during the quality control stage before distribution.
Often, the test results of the product should fall within a range of values in order for the product to “pass”. These validation tests performed with a system whose calibration certifications have expired may produce inaccurate results, which may eventually lead to a company distributing non-conforming products.
It is important to maintain an up-to-date calibration schedule in order to minimize the potential of manufacturing errors within a company. Inaccurate test results can lead a user to inaccurate conclusions about a test specimen in research and development laboratories, distorting the proposed findings.
Therefore, testing laboratories should maintain certification through calibration in order to ensure that they can reliably perform tests requested by their customers. In most environments where universal testing machines are employed, it is important that the measurement devices connected with the machine be as accurate as possible. Hence, it is important, and for some companies necessary, to maintain a frequent and consistent calibration schedule.
How Often Should A System be Calibrated?
Accredited calibration certificates normally expire after one year. ADMET recommends that measurement devices integrated into a materials testing system must be calibrated annually, at a minimum, in order to ensure that the users’ materials testing system provides precise and accurate measurements. Users must review their calibration certificates annually in order to see if any devices have deviated significantly with regard to accuracy. This reduces the risk of generating invalid results.
Besides regular scheduled calibration, several ISO and ASTM standards, such as ASTM E4, require a system to be re-calibrated after a move. In addition, certain industries might be subject to other regulations which require more frequent calibrations.
How is Calibration Performed?
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Image Credit: Admet Inc.
ADMET technicians use the company’s Gauge Buster 2 Portable Calibration unit in order to calibrate measurement devices on a materials testing system.
When a materials testing system is calibrated, the measurement device’s reference points are checked in comparison to a device calibrated to a recognized traceable standard laboratory, such as NIST. Internationally recognized standards determine the calibration procedures. For instance, ASTM E4 specifies compression and tension force calibration procedures.
The positions of the reference points that have to be calibrated are determined by the standard and checked on an initial run. This verification is repeated again for a second time. The measurement device passes and the calibration is verified if the error on each run and the repeatability calculations display error <1%. If the errors are >1%, the service technician will have to manually adjust values of the measurement device’s calibration so that the measurements can match the target range of the calibrated device.
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Who Can Carry Out Calibration on A System?
If customers are interested in learning more about calibration, or would like to get estimation for the calibration of their universal testing system, they can contact one of the company’s sales engineers.
The company’s sales engineers work directly with customers in order to properly decide components of their system’s calibration, and they also work with the scheduling department to provide the customers with quick and suitable calibration dates.
This information has been sourced, reviewed and adapted from materials provided by Admet, Inc. - Materials Testing Equipment.
For more information on this source, please visit Admet, Inc. - Materials Testing Equipment.