ASTM E4 | Universal Testing Machines | Calibration
ASTM E4 describes the procedures for the force verification of tension or compression, or both, static or quasi-static testing machines. A testing machine consists of the load frame, force sensing device, force display or readout, grips or fixtures, and any other components used for regular testing procedures. Force reading of such testing machines provides accurate load results if the indicated force is within the specified permissible variation from the actual force and this may be verified using standard weights, standard weights and equal-arm balances, or elastic calibration devices.
Force-indicating systems associated with the testing machine verified per ASTM E4 are within ±1% accuracy. The repeatability, which is the algebraic difference between errors of two applications of the same force of the runs, is also required to be less than or equal to ±1.0% to be compliant with the procedure.
By following the procedures in this standard, the accuracy of the force that is applied and indicated becomes known and traceable to the National Institute of Standards and Technology (NIST). Please note that for ASTM E4 calibration, verification devices need to be previously calibrated in accordance with ASTM E74 and the performing calibrator
Before conducting ASTM E4, it is important to read the entire specification in the relevant ASTM publication.
ASTM E4 | Universal Testing Machines | Calibration
- Place a calibrated thermometer near the load cell to monitor ambient conditions during the procedure.
- Allow the calibration load cell or dead weights to stabilize at ambient temperature for at least 20 minutes.
- Record the resolution of the digital readout as the change in force at the least significant digit.
- Determine the upper and lower limits of the testing machine
- Make sure all appropriate safety procedures are followed.
- Never use a load frame, calibration load cell, or tension adaptors above their rated force limits.
- A minimum of two runs of readings is required so that “As Found” and “As Left” data is recorded. If adjustments are required or made after the “As Found” readings, an additional two runs of readings shall be recorded for the “As Adjusted” and “As Left” readings.
- When a testing machine system is comprised of multiple load cells or a new force sensing device is installed, establish interchangeability by removing and reinstalling the force transducer between the calibration runs.
- If an out of tolerance condition is noted, record this data and include it in the calibration certificate.
- Test frames that are used in tension and compression shall be calibrated in both directions.
- Always apply and record calibration readings in the increasing force direction and never on a relaxing load.
ASTM E4 | Universal Testing Machines | Calibration
| ASTM E4 | Recommended Equipment |
|---|---|
| Calibration Equipment |
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