The NASA Metrology and Calibration (MetCal) Program released a new course in SATERN, “4:1 Test Accuracy Ratio for Compliance with ANSI/NCSL Z540.1-1994 (R2002) Sub-clause 10.2.b,” (SMA-HQ-WBT-217).

“The course is intended to familiarize trainees with the Test Accuracy Ratio [TAR] to enable consistent implementation of the TAR for calibrations performed to the requirements of Z540.1,” explained Ken Mathews, MetCal Program manager.

NASA-STD-8739.12, Metrology and Calibration, requires centers to implement one of three voluntary consensus standards for calibration of Measuring and Test Equipment (MTE): ANSI/NCSL Z540.1, ANSI/NCSL Z540.3 or ISO/IEC 17025. Each of these standards include requirements that apply to calibrations performed on NASA MTE. To date, Z540.1 is the most widely used of the three standards.

The 4:1 TAR is the primary technical requirement in Z540.1 for ensuring the correct selection of calibration standards that are used to perform a calibration process. A TAR of 4:1 means that the tolerance of an MTE parameter being calibrated is equal to or greater than four times the combination of the uncertainties of the measurement standards being used.

This course covers topics necessary to understand the TAR and to meet the 4:1 TAR requirement in Z540.1, including

• Definition of the TAR
• Equipment specifications, which are the basis for TAR calculation
• Formula and process for TAR calculation
• Example TAR calculations
• Use of guard bands for cases where the TAR is below 4:1
• Objective evidence for demonstrating compliance with the TAR requirement

This course is for anyone that performs calibrations of MTE and for anyone responsible for managing or auditing those calibration activities. This includes

• Calibration laboratory personnel
  • Lab managers
  • Engineers
  • Quality managers
  • Technical managers
  • Calibration technicians
  • Internal auditors
• NASA organizations
  • NASA representatives that provide oversight in contractor labs
  • Auditors that audit calibration labs
  • Program engineers and technicians that calibrate their own MTE
  • Quality personnel that provide oversight of those calibrations

Questions can be directed to Mathews.