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# A-GEN101-202-EN Measurement Accuracy

```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 &amp; 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: &plusmn;(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 &micro;Ω shunt. Instrument's maximum reading error is
0,1%, and maximum full scale error is also 0,1%.
0,1% of 100 &micro;Ω is 0,1 &micro;Ω.
An instrument range selected for a resistance of 100 &micro;Ω could be, for example, 999,9 &micro;Ω.
0,1% of 999,9 &micro;Ω is 1 &micro;Ω.
Typical accuracy in this case would be &plusmn; (0,1 &micro;Ω + 1 &micro;Ω), ie. &plusmn; 1,1 &micro;Ω. This means the obtained value
of the resistance should be within the range of 98,9 &micro;Ω and 101,1 &micro;Ω i.e. (100 &micro;Ω – 1,1 &micro;Ω; 100 &micro;Ω +
1,1 &micro;Ω). If not, instrument's accuracy is out of the range &plusmn;(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 &micro;Ω value. Typical accuracy in this case would also be &plusmn;(0,1 &micro;Ω + 1 &micro;Ω), ie. &plusmn;
1,1 &micro;Ω. This means the true value of the resistance is within the range of 98,9 &micro;Ω and 101,1 &micro;Ω i.e.
(100 &micro;Ω – 1,1 &micro;Ω; 100 &micro;Ω + 1,1 &micro;Ω).
Typical accuracy of RMO series is shown in the table below.
Measuring ranges
Resolution
0,1 &micro;Ω - 999,9 &micro;Ω
1,000 mΩ - 9,999 mΩ
10,00 mΩ - 99,99 mΩ
100,0 mΩ - 999,9 mΩ
0,1 &micro;Ω
1 &micro;Ω
10 &micro;Ω
0,1 mΩ
Full scale
(FS)
999,9 &micro;Ω
9,999 mΩ
99,99 mΩ
999,9 mΩ
0,1% FS
Typical accuracy
1 &micro;Ω
10 &micro;Ω
0,1 mΩ
1 mΩ
&plusmn;(0,1% rdg + 0,1% FS)
A-GEN101-202-EN
1
IBEKO Power AB
Box 1346
181 25 Liding&ouml;
Sweden
IBEKO Power AB
Stockholmsv&auml;gen 18
181 50 Liding&ouml;
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 &micro;Ω - 999,9 &micro;Ω
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 &micro;Ω
1 &micro;Ω
10 &micro;Ω
0,1 mΩ
1 mΩ
10 mΩ
0,1 Ω
1Ω
Full scale
(FS)
999,9 &micro;Ω
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 &micro;Ω
10 &micro;Ω
0,1 mΩ
1 mΩ
10 mΩ
0,1 Ω
1Ω
10 Ω
&plusmn;(0,1% rdg + 0,1% FS)
Typical accuracy of RMO-M device is shown in the table below.
Measuring ranges
Resolution
0,1 &micro;Ω - 999,9 &micro;Ω
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 &micro;Ω
1 &micro;Ω
10 &micro;Ω
0,1 mΩ
1 mΩ
10 mΩ
0,1 Ω
Full scale
(FS)
999,9 &micro;Ω
9,999 mΩ
99,99 mΩ
999,9 mΩ
9,999 Ω
99,99 Ω
999,9 Ω
0,1% FS
Typical accuracy
1 &micro;Ω
10 &micro;Ω
0,1 mΩ
1 mΩ
10 mΩ
0,1 Ω
1Ω
&plusmn;(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-DL
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
&plusmn; (0,25% rdg + 0,25% FS)
A-GEN101-202-EN
2
IBEKO Power AB
Box 1346
181 25 Liding&ouml;
Sweden
IBEKO Power AB
Stockholmsv&auml;gen 18
181 50 Liding&ouml;
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
&plusmn; (0,5% rdg + 0,5% FS)
Typical accuracy
&plusmn; (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 &amp; 80 V AC
@40 V AC
@10 V &amp; 8 V AC
0,8 - 999: &plusmn;0,05%
0,8 - 999: &plusmn;0,05%
0,8 - 999: &plusmn;0,05%
1000 - 3999: &plusmn;0,05%
1000 - 3999: &plusmn;0,1%
1000 - 3999: &plusmn;0,1%
4000 - 15000: &plusmn;0,1%
4000 - 15000: &plusmn;0,2%
4000 - 15000: &plusmn;0,2%
Typical ratio accuracy of TRT3x series devices is shown in the table below.
@100 V &amp; 80 V AC
@40 V AC
@10 V &amp; 8 V AC
@1 V AC
0,8 - 999: &plusmn;0,05%
0,8 - 999: &plusmn;0,05%
0,8 - 999: &plusmn;0,05%
0,8 - 999: &plusmn;0,05%
1000 - 3999: &plusmn;0,05%
1000 - 3999: &plusmn;0,1%
1000 - 3999: &plusmn;0,1%
1000 - 3999: &plusmn;0,1%
4000 - 15000: &plusmn;0,1%
4000 - 15000: &plusmn;0,2%
4000 - 15000: &plusmn;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: &plusmn;0,05%
0,8 - 999: &plusmn;0,05%
0,8 - 999: &plusmn;0,05%
0,8 - 999: &plusmn;0,05%
1000 - 3999: &plusmn;0,05%
1000 - 3999: &plusmn;0,1%
1000 - 3999: &plusmn;0,1%
1000 - 3999: &plusmn;0,1%
4000 - 15000: &plusmn;0,1%
4000 - 15000: &plusmn;0,2%
4000 - 15000: &plusmn;0,2%
A-GEN101-202-EN
3
IBEKO Power AB
Box 1346
181 25 Liding&ouml;
Sweden
IBEKO Power AB
Stockholmsv&auml;gen 18
181 50 Liding&ouml;
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 &amp; 80 V AC
@40 V AC
@10 V &amp; 8 V AC
@1 V AC
0,8 - 999: &plusmn;0,03%
0,8 - 999: &plusmn;0,05%
0,8 - 999: &plusmn;0,05%
0,8 - 999: &plusmn;0,05%
0,8 - 999: &plusmn;0,05%
1000 - 3999: &plusmn;0,05%
1000 - 3999: &plusmn;0,05%
1000 - 3999: &plusmn;0,1%
1000 - 3999: &plusmn;0,1%
1000 - 3999: &plusmn;0,1%
4000 - 14999: &plusmn;0,05%
4000 - 14999: &plusmn;0,1%
4000 - 14999: &plusmn;0,2%
4000 - 14999: &plusmn;0,2%
15000 - 19999: &plusmn;0,05%
15000 - 19999: &plusmn;0,2%
15000 - 19999: &plusmn;0,3%
20000 - 50000: &plusmn;0,1%
20000 - 50000: &plusmn;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
&plusmn;(0,25% rdg + 500 μA)
0 – 360 Degrees
&plusmn; 0,05 Degrees
A-GEN101-202-EN
4
IBEKO Power AB
Box 1346
181 25 Liding&ouml;
Sweden