ix
────────────────────────────────────────────────────
Notes on Using the Power Meter
────────────────────────────────────────────────────
NOTE
otes on Using the Power Meter
・This power meter uses the calculations indicated in the specifications in
order to determine apparent power (S), power factor (λ), and calculated
reactive power on the basis of the measured voltage (U), current (I), and
active power. In the 3166, the apparent power (S), power factor (λ), and
calculated reactive power (Q) are calculated according to formulas indicated
in the specifications, based on the voltage (U), the current (I), and the active
power (P). In addition, when using the active power meter method, the
apparent power (S) and power factor (λ) are derived from the measured
active power (P) and reactive power (Q). The values displayed by this power
meter may differ from those produced by other testers that are based on
different principles of operation or testers that use different calculations.
It should be noted that if the measurement line is a three-phase three-wire
line and the waveform is distorted (e.g., on the primary side of the inverter),
the values of reactive power (Q), apparent power (S), and power factor (λ)
differ from those on a measuring instrument based on a different calculation
formula.
・The integrated values produced by this power meter are derived through
software calculations based on the power measurements. The integrated
value may differ from the value produced by a tester that has a different
response speed, sampling rate, or calculation method. In addition, this
power meter is designed specifically to measure alternating current, and
cannot be used to measure lines carrying direct current.
The power factor is calculated for display using the values of active power
and apparent power before zero-suppression. Note that even if the active
power (P) and apparent power (S) on display are zero, the power factor (λ)
may not be zero.
In order to assure accurate measurements, allow this unit to warm up for at
least 30 minutes before using it. The displayed value is forced to zero for
inputs that are 0.4% or less of the measurement range. (zero suppress
function) Although this power meter has a frequency measurement
function, proper measurement may not be possible in cases where the input
waveform is clearly distorted.
・When using external transformers (PT and CT), the phase difference may
introduce a large error into power measurements. For accurate
measurements, use PTs and CTs with as small a phase difference as
possible.
・When the voltage or current on the line being measured exceeds the
measurement range of this power meter, use an external PT and CT, and do
not exceed the maximum allowed input. When using a PT and CT, use the
scaling function and take direct readings.
To Next Page
