YOKOGAWA WT500 User Manual page 309

14.5 Accuracy
Power Accuracy
Item
Accuracy (at 6 months)
Effective input range
Lower limit of measurement
frequency
Power factor influence
(not including when λ
= 1)
14-8
Specifications
Conditions
Same as the conditions for the voltage and current accuracies.
Frequency
DC
0.5 Hz ≤ f < 45 Hz
45 Hz ≤ f ≤ 66 kHz
66 Hz < f ≤ 1 kHz
1 kHz < f ≤ 10 kHz
10 kHz < f ≤ 100 kHz
• For the external current sensor range, add (50
100% to the DC power accuracy.
• For the directly applied current input range, add (500
× 100% of range to the DC power accuracy.
• Influence of temperature changes after zero-level compensation or range change.
DC voltage accuracy: add 0.02% of range/°C. DC current accuracy for direct input: add 500
µA/°C. DC voltage accuracy for external sensor input: add 50 µV/°C. DC power accuracy: add
the product of the voltage influence and the current influence.
• Influence of self-generated heat caused by voltage input
2
Add 0.0000001 × U % of reading to the power accuracies. Add 0.0000001 × U
2
0.0000001 × U of range to the DC current and voltage accuracies. U is the voltage reading (V).
Even if the voltage input decreases, the influence from self-generated heat continues until the
temperature of the input resistor inside the WT500 decreases.
• Influence of self-generated heat caused by current input
2
Add 0.00013 × I % of reading to the power accuracies. Add 0.00013 × I
× I% of reading to the DC current and voltage accuracies. I is the current reading (A).
Even if the current input decreases, the influence from self-generated heat continues until the
temperature of the shunt resistor inside the WT500 decreases.
• Accuracy changes caused by data update interval
When the data update interval is 100 ms, add 0.05% of reading to all accuracy figures.
• Guaranteed accuracy ranges for frequency, voltage, and current
All accuracy figures for 0.1 to 10 Hz are reference values.
The power accuracy figures for 30 kHz to 100 kHz when the voltage exceeds 750 V are
reference values.
The power accuracy figures for DC, 10 Hz to 45 Hz, and 400 Hz to 200 kHz when the current
exceeds 20 A are reference values.
0 to ±110% of the measurement range for DC power. For AC, current and voltage are 1 to ±110% of
the measurement range and power is up to ± 110%.
However, the synchronization source signal level must meet the frequency measurement input
signal level (see section 14.6 for details).
* 100% for the maximum voltage range.
Same as the lower limits for the voltage and current measurement frequencies.
λ
• When = 0
Apparent power reading × 0.2% in the range of 45 to 66 Hz.
For other frequency ranges, see below. However, be aware that these figures are reference
values.
Apparent power reading × (0.2 + 0.2 × f (kHz))%
λ
• When 0 < < 1
(Power reading) × [(power reading error %) + (power range error %) × (power range/indicated
apparent power value) + {tan
f
where is the phase angle between the voltage and current.
Accuracy
±(reading error + measurement range error)
0.1% of reading + 0.1% of range
0.3% of reading + 0.2% of range
0.1% of reading + 0.1% of range
0.2% of reading + 0.2% of range
{0.1 + 0.067 × (f – 1)}% of reading + 0.3% of range
{5.1 + 0.18 × (f – 50)}% of reading + 0.3% of range
* The unit of f in the reading-error equations is kHz.
µ
V / external current sensor range rating) ×
µ
A / external current sensor range rating)
*
f λ
× (influence when = 0%)}]
2
% of reading +
2
% of reading + 0.0004
IM 760201-01E