Microchip Technology ARD00330 データシート
Meter Calibration
© 2011 Microchip Technology Inc.
DS51964A-page 15
2.3.2.2
ACTIVE ENERGY GAIN COMPUTATION
Active energy gain is computed as the percentage ratio of the error recorded against
the previous gain. The Error % is the difference between the input line active energy
and the meter output as recorded by the reference meter. Active energy gain is com-
puted using Equation 2-1.
the previous gain. The Error % is the difference between the input line active energy
and the meter output as recorded by the reference meter. Active energy gain is com-
puted using Equation 2-1.
EQUATION 2-1:
ACTIVE ENERGY GAIN COMPUTATION
2.3.2.3
PHASE COMPENSATION
Due to reactive components in the signal flow path, the voltage and current may not be
in phase at PF = 1.0. Therefore, the voltage and current samples measured will have
a small phase offset, that may affect the energy accuracy. To rectify the offset, phase
compensation is introduced, which shifts the voltage/current samples by corresponding
angle through an interpolation method.
in phase at PF = 1.0. Therefore, the voltage and current samples measured will have
a small phase offset, that may affect the energy accuracy. To rectify the offset, phase
compensation is introduced, which shifts the voltage/current samples by corresponding
angle through an interpolation method.
2.3.2.3.1
Phase Compensation Calculation
EQUATION 2-2:
ENERGY WITH PHASE ERROR AT PF = 1.0
EQUATION 2-3:
ENERGY WITH PHASE ERROR AT PF = 0.5 LAG
Then,
GAIN_NUMR_ENERGY_ACT
(New Value)
= GAIN (
New Value)
/ 2
GAIN_DENR_ENERGY_ACT
(New Value)
= GAIN_DENR_ENERGY_ACT
(Old Value)
+ 1
else,
GAIN_NUMR_ENERGY_ACT
(New Value
= GAIN
(New Value)
GAIN_DENR_ENERGY_ACT
(New Value)
= GAIN_DENR_ENERGY_ACT
(Old Value)
)
GAIN NewValue
(
)
GAIN OldValue
(
)
Error%
100
------------------
⎝
⎠
⎛
⎞
1
+
--------------------------------------------
=
If GAIN > 65535
Energy at PF = 1.0 ( Φ= 0
o
):
E
UPF
= V
RMS
x I
RMS
x Cos( Φ+ β) x Period = V
RMS
x I
RMS
x Cos( β) x Period
Where:
Φ = Input Phase between V and I
β = Phase deviation between V and I, β Є [-90°, +90°]
Energy at PF = 0.5 lag ( Φ= 60
o)
:
E
PF0.5_error
= V
RMS
x I
RMS
x Cos( Φ + β) x Period
= V
RMS
x I
RMS
x Cos( 60 + β) x Period
Where:
Φ = Input Phase between V and I
β = Phase deviation between V and I, β Є [-90°, +90°]