Material testing data is only as good as the measurement tools used. ASTM E83 addresses several key aspects of measurement quality:
The process of verifying an extensometer to ASTM E83 is a rigorous calibration procedure.
Step 1: Reference Standards The verification must be performed using a device capable of applying known displacements. Common devices include: astm e83 pdf
Step 2: Environmental Control The standard requires the test to be conducted within a specific temperature range (usually 20°C ± 2°C or similar) because thermal expansion can affect the calibration of both the extensometer and the reference standard.
Step 3: Mounting The extensometer is mounted onto the calibration rig in a manner identical to how it would be used on a specimen. Care must be taken to avoid applying torque or stress that could skew the reading. Material testing data is only as good as
Step 4: Data Collection The operator applies a series of displacements throughout the measuring range of the extensometer.
Step 5: Error Calculation For each calibration point, the error is calculated as: $$Error = \frac\textIndicated Strain - \textTrue Strain\textTrue Strain \times 100%$$ Step 2: Environmental Control The standard requires the
The absolute value of this error is compared against the table of allowable limits for the target Class.
One of the most misunderstood aspects of the standard is the "range of the extensometer." You cannot simply say "My extensometer is Class B-1." You must specify the strain range (e.g., Class B-1 from 200 µε to 2000 µε). Outside that verified range, the classification is void.