Magnetic Particle Equipment Accuracy and Repeatability

With the publication of the latest revisions of ASTM E1444 (2011 with a subsequent update in 2012), there was a significant change in Quality Control requirements for ammeters used on Magnetic Particle equipment. The requirements now include not only ammeter accuracy, but also repeatability. The changes to ASTM E1444 have prompted a series of updates to the NADCAP audit criteria, which has caused a bit of confusion across users and subscribers alike. This paper will illustrate the methods of ammeter calibration in order to meet the latest criteria for accuracy and repeatability. The process would apply to all waveforms (AC, HWDC, single-phase FWDC, three-phase FWDC), and it includes establishing a lowest repeatable current level. Naturally, the specific and detailed procedures will vary from manufacturer to manufacturer, as well as from model to model depending on the configuration and options used. However, the methods described will provide general guidance for meeting the latest ASTM and NADCAP requirements.

References
  1. Standard Practice for Magnetic Particle Testing, E1444/E1444M-05, ASTM International, West Conshohocken, PA, 2005.
  2. Standard Practice for Magnetic Particle Testing, E1444/E1444M-11, ASTM International, West Conshohocken, PA, 2011. 51
  3. NADCAP Audit Criteria for Nondestructive Testing Facility, Magnetic Particle Survey, AC 7114/2 Rev F, Performance Review Institute, Warrendale, PA, 2012.
  4. NADCAP Audit Criteria for Nondestructive Testing Facility, Magnetic Particle Survey, AC 7114/2 Rev G, Performance Review Institute, Warrendale, PA, 2013.
  5. NADCAP Audit Criteria for Nondestructive Testing Facility, Magnetic Particle Survey, AC 7114/2 Rev H, Performance Review Institute, Warrendale, PA, 2014.
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