norbar TWC 400 AUTO Operator's Manual

Contents

norbar TWC 400 AUTO Operator's Manual Manual pdf 38 page image

36How to Fill in Uncertainty Data1. Refer to the final page of your TWC/transducer calibration; the page should be titled “Expression ofUncertainties”For Transducers:On the “Expression of Uncertainties” page, you should see a table like the following (shown here, anexample for a 400 N·m transducer):Expanded uncertainty k=2.0 Uncertainty interval k=2.0At 20.00 N·m ±0.15% ±0.38%At 40.00 N·m ±0.12% ±0.18%At 80.00 N·m ±0.099% ±0.11%At 160.00 N·m ±0.087% ±0.11%At 240.00 N·m ±0.087% ±0.13%At 320.00 N·m ±0.084% ±0.12%At 400.00 N·m ±0.084% ±0.11%First, fill in the “BOS Expanded” and “BOS Interval” values for the bottom of scale; these come from theexpanded uncertainty and the uncertainty interval at the very lowest reading, in this case 20 N·m. Thatmeans the BOS Expanded field is 0.15% and the BOS Interval field is 0.38%.Next fill in the 5% Expanded and 5% Interval fields using the readings at 5% of transducer capacity. Inthis case, this is the same as the BOS Expanded and BOS Interval values, because in our example, thetransducer’s bottom of scale is 5%.Repeat the same procedure for the 10% fields using the readings at 10% of transducer capacity (in thiscase, the Expanded field is 0.12% and the Interval field is 0.18%)For the final two fields, we need to select the worst-case (largest) expanded uncertainty of theremaining transducer range equal to and above 20% of transducer capacity, and its correspondinguncertainty interval. This is usually the next field on from the 10% readings anyway, and indeed this is thecase in our example: therefore, the Expanded field should be 0.099% and the Interval field should be 0.11%.For the TWC (If Instrument Calibrated):On the TWC certificate’s expression of uncertainties, you should see the following (shown here, an examplefor a TWC):At 0.50mV Is ±0.20% k=2.0At 1.00mV Is ±0.13% k=2.0At 2.00mV to 11.00mV Is ±0.11% k=2.0The percentages here tally up with the mV values, so 0.50mV is the 5% value, 1.00mV is 10%, and so on.Enter all three percentage values from the table in the 5%, 10% and 20% fields respectively. In this example,the 5% Expanded field is 0.20%, the 10% Expanded field is 0.13%, and the 20% Expanded field is 0.11%.IMPORTANT: BE EXTREMELY CAREFUL YOU ENTER THE CORRECT VALUES IN THESEFIELDS. DOUBLE AND TRIPLE CHECK TO MAKE SURE. IF YOU DO NOT ENTERTHE CORRECT VALUES, ANY CALIBRATIONS OR CONFORMANCE JOBSPERFORMED BY THE TWC MAY BE RENDERED INVALID.