Force Calibration to ASTM E4
ASTM E4 is one of two internationally recognized standard methods for verifying the force measuring capabilities of a universal testing machine. ASTM E4 and its ISO counterpart ISO 7500-1 are technically rigorous standards that have been developed over many years to ensure that the force measuring system of a calibrated testing instrument is accurate under static or quasi-static conditions.
ASTM E4 defines the standard practices required to measure the tensile and/or compressive strength of testing machines. A system is considered to be in compliance if the force indicating system associated with the machine is within ±1.00%, with a maximum repeatability of 1.00%.
How Does ASTM E4 Differ from ISO 7500-1?
ASTM E4 specifies that the testing machine be accurate to 1% of reading over the verified range. This is very different from 1% of full-scale, which is how some suppliers spec their product. ISO 7500-1 defines several accuracy classes ranging from 0.5 to 3. Most materials testing machines are calibrated to ISO 7500-1 Class 1, which is equivalent to the ASTM E 4 requirement of 1.0%. Instron maintains its calibration standards at the accuracy level required to calibrate instruments to 0.5%, so this option is available at no cost if required.
Which Verification Standard Should I Use?
For a majority of test system users, verifying equipment to either of the two major standards (ISO7500-1 or ASTM E 4) is a low-risk way to ensure that the calibration of force transducers is done properly and that the probability of the instrument providing bad data is minimal. These standards provide a reasonable balance between the cost and difficulty of performing the verification and the quality of the results. The accepted practice is to verify systems in North America to ASTM E4 and systems in Europe to ISO 7500-1, while other regions vary based on local requirements.
Can Instron Calibrate my System to ASTM E4/ISO 7500-1?
Instron’s calibration services not only meet the international standards for force calibration, they also routinely exceed them. Our factory-trained technicians can carry out full system and load cell calibrations at your site or in one of our force calibration laboratories.
The Instron force calibration laboratory can calibrate your load cells using primary standards up to 575 kN (130,000 lbf) and secondary standards up to 1 MN (240,000 lbf). Instron can accommodate most calibration methods, including ASTM E 74, ISO 376, or special testing specified by the customer. The calibration method can be verified in tension, compression, or both modes, and can consist of increasing and decreasing loads. We can also provide full hysteresis analysis of your load cell with both an increasing and decreasing load calibration.
ASTM E 74 calibrations provided by Instron allow your load cells up to 575 kN (130,000 lbf) capacity to be used as secondary standards over the Class AA range (0.05% max error). Load cells calibrated between 575 kN up to our capacity of 1 MN (240,000 lbf), may be used over the Class A range (0.25% max error) for performing ASTM E 4 material testing system force verifications. We can also specify special load ranges, as allowed by ASTM E 74, to meet any of your testing needs.
Our low uncertainties of measurement for ISO 376 calibrations allow your load cells to meet the best possible classes of 00 and 0.5 up to our full capacity of 1 MN (240,000 lb). This allows you to verify your testing systems to the 0.5, class per ISO 7500-1 specifications.
Instron offers both Standard and Enhanced verification packages. Standard verification will verify your system to meet the requirements of ASTM E4/ISO 7500-1. Enhanced verification exceeds the standard requirements by verifying the full capacity range of your individual system. Enhanced verification may benefit you if your test methods or requirements change frequently, or if you routinely produce test results at the boundaries of your verification range.