Hioki PW3335 - Appendix 3 Example Accuracy Calculations

Appendix 3 Example Accuracy Calculations
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Basic approach to accuracy
When the accuracy notation combines rdg. and f.s.
Accuracy specification: ±0.2% rdg. ±0.1%f.s.
Measurement range: 300.00 V
Measured value: 100.00 V
Since the value being measured is 100.00 V;
(A) Reading error (±% rdg.): ±0.2% of 100.00 V = ±0.20 V
(B) Full-scale error (±%f.s.): ±0.1% of 300 V = ±0.30 V
(C) Total error (A+B): ±0.50 V
Based on the total error (C), the error boundary values for a measured value of 100.00 V would be
99.50 V to 100.50 V
.
Method for calculating accuracy when using a current sensor
Power measurement error = Instrument’s measurement error + 9661 Current Sensor additional error
Example calculation: If input is less than 50% of the range
Measurement conditions
Voltage range of 300 V, current range of 200 A (2 A range, CT ratio: 100), power display value of 16 kW
Voltage input of 200 V, current input of 80 A, 50 Hz, sine wave
• Effective power accuracy of instrument’s external current sensor input: ±0.1% rdg. ±0.1%f.s.
(Representative accuracy when input is less than 50% of the range)
• 9661 measurement accuracy: ±0.3%rdg. ±0.01%f.s.
Calculation method
1. Check the instrument’s power range in the instruction manual.
Voltage range: 300 V
, Current range: 200 A (2 A range, CT ratio: 100)  60.000 kW range
2. Calculate the instrument’s error.
±(16 kW
× 0.1%) rdg. ±(60 kW × 0.1%)f.s. = ±0.076 kW
3. Check the power range to use when calculating the 9661’s accuracy addition.
Since the sensor is the 9661, use the power range for the 500 A current range (5 A range, CT ratio: 100)
for f.s.*
Voltage range: 300 V
, Current range: 500 A (5 A range, CT ratio: 100)  150 kW range
4. Calculate the additional power accuracy when using the 9661.
±(16 kW
× 0.3%) rdg. ±(150 kW × 0.01%)f.s. = ±0.063 kW
5. Add the instrument’s error and the 9661 error.
±0.076 kW ±0.063 kW = ±0.139 kW
• • • ±0.87% rdg.
* Since the current sensor itself has no power range, use the power meter’s power range when calculating the
f.s. error.
Appendix 3 Example Accuracy Calculations