Hioki CM7290, Инструкция по эксплуатации, Страница: 66 / 80

Appx.2
Calculating Accuracy When Used with a Sensor
Appx. 2 Calculating Accuracy When
Used with a Sensor
The following examples illustrate how to calculate accuracy when measuring
a 58.00 A, 60 Hz current (with the instrument set to the
×
10 range and AC
measurement) when using the CT7631 (with a rating of 100 A and a sensor
output rate of 1 mV/A).
(1) Example of how to calculate display accuracy
Sensor accuracy: ±1.0% rdg. ±0.5% f.s.
Instrument accuracy: ±0.3% rdg. ±8 dgt.
Combined % rdg. accuracy: = (Sensor % rdg. ac instrument % rdg. accuracy)
= ±(1.0% rdg. +0.3% rdg.)
= ±1.3% rdg.
Combined A accuracy = (Sensor % f.s. accuracy × sensor rating) + (0.1 × instrument
dgt. accuracy) / (Sensor output rate × instrument range)
= 0.5% f.s. × 100 A + (0.1 × 8) / (1 × 10) A
= 0.5 A + 0.08 A
= 0.58 A
Above combined accuracy = ±1.3% rdg. × 58 A ±0.58 A
= ±0.754 A ±0.58 A
= ±1.334 A
Consequently, the accuracy for a measured value of 58.00 A is ±1.334 A.
(2) Example of how to calculate WAVE output accuracy
Sensor accuracy: ±1.0% rdg. ±0.5% f.s.
Instrument accuracy: ±0.5% rdg. ±0.8 mV
Combined output rate = Sensor output rate × instrument range
= 1 mV/A × 10
Combined % rdg. accuracy = (Sensor % rdg. ac instrument % rdg. accuracy)
= ±1.5% rdg.
Combined mV accuracy = Sensor % f.s. accuracy × sensor rating × combined output
rate + instrument mV accuracy
= 0.5% f.s. × 100 A × (1 mV/A × 10) + 0.8 mV
= 5 mV + 0.8 mV
= 5.8 mV
Above combined accuracy (mV equivalent) = ±1.5% rdg. × 58 A × (1 mV/A × 10) ±5.8 mV
= ±8.7 mV ±5.8 mV
= ±14.5 mV
Instrument output value = Display value × combined output rate
= 58.00 A × (1 mV/A × 10)
= 580 mV
Consequently, the accuracy for an instrument output value of 580.0 mV is ±14.5 mV.