MIL-HDBK-1839A
"3.4 Measurement traceability. The property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties. Traceability, as used in this standard, applies to measurements/calibrations made from the prime system or subsystem through an unbroken chain of comparisons to the national reference standards."
Interpretive guidance: It is the intent of the Calibration and Measurement Requirements Summary (CMRS), (see APPENDIX A for FREQUENTLY ASKED QUESTIONS and APPENDIX B for an example of a CMRS) to document the traceability of the measurement from the prime system, (e.g., F/A-18, B-2, V-22, M1A2, CASS, etc) through an unbroken chain of calibrated TMDE and calibration laboratories to either a national standard or a physical constant. In effect, the CMRS outlines traceability for each measurement from the prime system level through the SE, and through the calibration standard(s) to the National Institute of Standards and Technology (NIST) the United States Naval Observatory (USNO) or other recognized reference standards.
"3.5 Test Uncertainty Ratio (TUR). The total uncertainty of the unit to be measured or calibrated divided by the total uncertainty of the measuring or generating device used to perform the measurement. For example, if it is required that a system or equipment output parameter's uncertainty is 8% and the uncertainty of the measuring device used to measure the output parameter is 2%, then the TUR is 8 to 2 or 4 to 1."
Interpretive guidance: The desired TUR is 4 to 1. TUR is the calculated result of dividing the uncertainty or tolerance of a measurement/input requirement by the uncertainty/tolerance of the equipment satisfying the requirement. TURs are generally calculated for each operational system test requirement that is supported by SE and for SE supported (calibrated) by SE. The maximum permitted uncertainty should reflect the actual use requirement of the unit being measured/calibrated for the intended use. Tolerances used in TUR calculations will be in the same measurement units.
Uncertainties expressed in logarithmic units such as decibels should be considered. Decibels should first be converted to linear units before computing TUR. For example, suppose the system uncertainty and the measurement uncertainty is 4db and 1db respectively. The db ratio may be 4 to
1 but the linear ratio may be only 2 to 1 or a 3db gain is generally double in value when dealing with power measurements. Caution should be used when uncertainties are stated as percentages because they often are not related (i.e. percentage of full scale versus percentage of reading). Tolerances expressed as "minimum", "maximum", "less than", "more than", "greater than" and
"less than", do not allow TURs to be calculated, thus using them is not desired. However, when no other option exists, the design activity should specify the recommended uncertainty of the supporting equipment (see 5.4.3).
"3.6 Logistics Support Analysis (LSA). The selective application of scientific and engineering efforts undertaken during the acquisition process, as part of the system engineering and design process, to assist in complying with supportability and other Integrated Logistics Support (ILS) objectives. The LSA process is a planned series of tasks performed to examine all elements of a proposed system to determine the logistics support required to keep that system useable for its intended purpose; and to influence the design so both the system and support can be provided at an affordable cost."
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