Stockholm, 2016-11-29 Application Note Measurement Accuracy In the fields of engineering, industry and statistics, the accuracy of a measurement system is the degree of closeness of measurements of a quantity to its actual (true) value. Accuracy of our instruments depends on two components: measured value, and instrument range, and is defined that way. Typical accuracy of DV Power measuring instruments RMO, RMO-T, TWA, RMO-M, POB & SAT series is specified as the sum of maximum reading error (rdg) expressed in percents (%), plus full scale (FS) maximum error in percents. As an example: ±(0,1% rdg + 0,1% FS). Maximum reading error is the highest deviation allowed for a particular measured value. Full scale is the maximum value that can be measured for a given measurement range. Example 1. We measure resistance of the 100 µΩ shunt. Instrument's maximum reading error is 0,1%, and maximum full scale error is also 0,1%. 0,1% of 100 µΩ is 0,1 µΩ. An instrument range selected for a resistance of 100 µΩ could be, for example, 999,9 µΩ. 0,1% of 999,9 µΩ is 1 µΩ. Typical accuracy in this case would be ± (0,1 µΩ + 1 µΩ), ie. ± 1,1 µΩ. This means the obtained value of the resistance should be within the range of 98,9 µΩ and 101,1 µΩ i.e. (100 µΩ – 1,1 µΩ; 100 µΩ + 1,1 µΩ). If not, instrument's accuracy is out of the range ±(0,1% rdg + 0,1% FS). Example 2. We measure resistance of a resistor with the same instrument as in previous example. Let's say we obtain 100 µΩ value. Typical accuracy in this case would also be ±(0,1 µΩ + 1 µΩ), ie. ± 1,1 µΩ. This means the true value of the resistance is within the range of 98,9 µΩ and 101,1 µΩ i.e. (100 µΩ – 1,1 µΩ; 100 µΩ + 1,1 µΩ). Typical accuracy of RMO series is shown in the table below. Measuring ranges Resolution 0,1 µΩ - 999,9 µΩ 1,000 mΩ - 9,999 mΩ 10,00 mΩ - 99,99 mΩ 100,0 mΩ - 999,9 mΩ 0,1 µΩ 1 µΩ 10 µΩ 0,1 mΩ Full scale (FS) 999,9 µΩ 9,999 mΩ 99,99 mΩ 999,9 mΩ 0,1% FS Typical accuracy 1 µΩ 10 µΩ 0,1 mΩ 1 mΩ ±(0,1% rdg + 0,1% FS) A-GEN101-202-EN 1 Postal address IBEKO Power AB Box 1346 181 25 Lidingö Sweden Delivery address IBEKO Power AB Stockholmsvägen 18 181 50 Lidingö Sweden Contact phone: +46 8 731 76 99 fax: +46 8 731 77 99 sales@dv-power.com Stockholm, 2016-11-29 Typical accuracy of RMO-T and TWA series is shown in the table below. Measuring ranges Resolution 0,1 µΩ - 999,9 µΩ 1,000 mΩ - 9,999 mΩ 10,00 mΩ - 99,99 mΩ 100,0 mΩ - 999,9 mΩ 1,000 Ω - 9,999 Ω 10,00 Ω - 99,99 Ω 100,0 Ω - 999,9 Ω 1000 Ω - 9999 Ω 0,1 µΩ 1 µΩ 10 µΩ 0,1 mΩ 1 mΩ 10 mΩ 0,1 Ω 1Ω Full scale (FS) 999,9 µΩ 9,999 mΩ 99,99 mΩ 999,9 mΩ 9,999 Ω 99,99 Ω 999,9 Ω 9999 Ω 0,1% FS Typical accuracy 1 µΩ 10 µΩ 0,1 mΩ 1 mΩ 10 mΩ 0,1 Ω 1Ω 10 Ω ±(0,1% rdg + 0,1% FS) Typical accuracy of RMO-M device is shown in the table below. Measuring ranges Resolution 0,1 µΩ - 999,9 µΩ 1,000 mΩ - 9,999 mΩ 10,00 mΩ - 99,99 mΩ 100,0 mΩ - 999,9 mΩ 1,000 Ω - 9,999 Ω 10,00 Ω - 99,99 Ω 100,0 Ω - 999,9 Ω 0,1 µΩ 1 µΩ 10 µΩ 0,1 mΩ 1 mΩ 10 mΩ 0,1 Ω Full scale (FS) 999,9 µΩ 9,999 mΩ 99,99 mΩ 999,9 mΩ 9,999 Ω 99,99 Ω 999,9 Ω 0,1% FS Typical accuracy 1 µΩ 10 µΩ 0,1 mΩ 1 mΩ 10 mΩ 0,1 Ω 1Ω ±(0,1% rdg + 0,1% FS) Note: Typical accuracies of RMO, RMO-T, TWA, and RMO-M devices are valid if the maximum possible test current is used. Typical accuracy of POB series devices is shown in the table below. Type POB-D POB-AD POB-AD POB-DL POB-ADL POB-ADL Measuring ranges Resolution Full scale (FS) 0,25% FS 10 V – 300 V DC 1V 300 V 0,75 V 10 V – 250 V AC 1V 250 V 0,625 V 1 V – 50 V DC 0,5 V 50 V 0,125 V 1 V – 40 V AC 0,5 V 40 V 0,1 V Typical accuracy ± (0,25% rdg + 0,25% FS) A-GEN101-202-EN 2 Postal address IBEKO Power AB Box 1346 181 25 Lidingö Sweden Delivery address IBEKO Power AB Stockholmsvägen 18 181 50 Lidingö Sweden Contact phone: +46 8 731 76 99 fax: +46 8 731 77 99 sales@dv-power.com Stockholm, 2016-11-29 Typical accuracy of SAT series is shown in the table below. Measuring ranges 1,0 Ω - 99,9 Ω 100 Ω - 999 Ω Resolution 0,1 Ω 1Ω Full scale (FS) 99,9 Ω 999 Ω 0,5% FS 0,5 Ω 5Ω Measuring ranges 10 V – 300 V DC 10 V – 250 V AC Resolution 1V 1V Full scale (FS) 300 V 250 V 0,25% FS 0,75 V 0,625 V Typical accuracy ± (0,5% rdg + 0,5% FS) Typical accuracy ± (0,25% rdg + 0,25% FS) Typical accuracy of Transformer Turns Ratio Tester TRT series is expressed either as a percentage (turns ratio accuracy) or in a measured units (excitation current accuracy and phase angle accuracy). Example 3. Let's say we measure transformer's ratio. The nominal ratio of the transformer is, for example, 10/0,4 kV/kV ie. 25. Instrument's ratio accuracy is, for example, 0,05%. 0,05% of 25 is 0,0125. This means the obtained value of ratio should be within the range of 24,9875 and 25,0125 i.e. (25 – 0,0125; 25 + 0,0125). If not, instrument's error is higher than 0,05%. Typical ratio accuracy of TRT03 series devices is shown in the table below. @100 V & 80 V AC @40 V AC @10 V & 8 V AC 0,8 - 999: ±0,05% 0,8 - 999: ±0,05% 0,8 - 999: ±0,05% 1000 - 3999: ±0,05% 1000 - 3999: ±0,1% 1000 - 3999: ±0,1% 4000 - 15000: ±0,1% 4000 - 15000: ±0,2% 4000 - 15000: ±0,2% Typical ratio accuracy of TRT3x series devices is shown in the table below. @100 V & 80 V AC @40 V AC @10 V & 8 V AC @1 V AC 0,8 - 999: ±0,05% 0,8 - 999: ±0,05% 0,8 - 999: ±0,05% 0,8 - 999: ±0,05% 1000 - 3999: ±0,05% 1000 - 3999: ±0,1% 1000 - 3999: ±0,1% 1000 - 3999: ±0,1% 4000 - 15000: ±0,1% 4000 - 15000: ±0,2% 4000 - 15000: ±0,2% Typical ratio accuracy of TRT4x series devices is shown in the table below. @125 V AC @40 V AC @8 V AC @1 V AC 0,8 - 999: ±0,05% 0,8 - 999: ±0,05% 0,8 - 999: ±0,05% 0,8 - 999: ±0,05% 1000 - 3999: ±0,05% 1000 - 3999: ±0,1% 1000 - 3999: ±0,1% 1000 - 3999: ±0,1% 4000 - 15000: ±0,1% 4000 - 15000: ±0,2% 4000 - 15000: ±0,2% A-GEN101-202-EN 3 Postal address IBEKO Power AB Box 1346 181 25 Lidingö Sweden Delivery address IBEKO Power AB Stockholmsvägen 18 181 50 Lidingö Sweden Contact phone: +46 8 731 76 99 fax: +46 8 731 77 99 sales@dv-power.com Stockholm, 2016-11-29 Typical ratio accuracy of TRT63 series devices is shown in the table below. @250 V AC @100 V & 80 V AC @40 V AC @10 V & 8 V AC @1 V AC 0,8 - 999: ±0,03% 0,8 - 999: ±0,05% 0,8 - 999: ±0,05% 0,8 - 999: ±0,05% 0,8 - 999: ±0,05% 1000 - 3999: ±0,05% 1000 - 3999: ±0,05% 1000 - 3999: ±0,1% 1000 - 3999: ±0,1% 1000 - 3999: ±0,1% 4000 - 14999: ±0,05% 4000 - 14999: ±0,1% 4000 - 14999: ±0,2% 4000 - 14999: ±0,2% 15000 - 19999: ±0,05% 15000 - 19999: ±0,2% 15000 - 19999: ±0,3% 20000 - 50000: ±0,1% 20000 - 50000: ±0,25% Typical excitation current and phase angle accuracy are shown in the table below. Excitation current range Typical excitation current accuracy Phase angle range Typical phase angle accuracy 0–2A ±(0,25% rdg + 500 μA) 0 – 360 Degrees ± 0,05 Degrees A-GEN101-202-EN 2016 DV Power, Sweden. All rights reserved. 4 Postal address IBEKO Power AB Box 1346 181 25 Lidingö Sweden Delivery address IBEKO Power AB Stockholmsvägen 18 181 50 Lidingö Sweden Contact phone: +46 8 731 76 99 fax: +46 8 731 77 99 sales@dv-power.com