A quick question about calculating measurement uncertainty. For example, if I am doing a conducted emission test, and I know the calibration tolerance for each of the "modules" of my measurement system, how do I calculate an overall uncertainty figure? I have been under the assumption that, in the example I cite, that I have a tolerance for my probe (say +/- 0.5 dB), my cable (+/- 0.1 dB) and my analyzer (+/- 1 dB). I have been using an "rms" calculation, where I square each of the tolerances, sum them, and take the square root. Thus, square root of 1.6 dB equals 1.26 dB uncertainty. I recently had a customer say that this method implied that I was using "rectangular" shape factors, and thus, I should be taking the cube root of the sum. Rectangular? Cube root? Ed Price [email protected] <blocked::mailto:[email protected]> WB6WSN NARTE Certified EMC Engineer Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 Military & Avionics EMC Is Our Specialty -
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