Analog Devices ADE9000 Technical Reference Manual page 12

UG-1098
INPUT
VOLTAGE
INPUT
CURRENT
CURRENT LAGS
VOLTAGE
DELAY I
BY 0°
DELAY V BY
ONE SAMPLE
°
2.25 AT 50Hz
°
I LAGS V BY UP TO 2.25
°
PHASE CORRECTION = +2.25
Figure 14. Phase Compensation Example where Current Lags Voltage
Using the previous equations, it can be seen that at 60 Hz, the
voltage channel delay is 2.7°:
°
Voltage Channel Delay
This leads to a phase calibration range of −15° to +2.7° at 60 Hz.
Multipoint Phase/Gain Calibration
The ADE9000 allows the current channel gain and phase
compensation to vary as a function of the calculated input
current rms amplitude in xIRMS. This feature corrects for the
nonlinearities of current transformer sensors to achieve very
high meter accuracy, for example in Class 0.2 meters.
Multipoint Gain and Phase
There is a current channel gain, xIGAIN, that is applied regardless
of the xIRMS input signal level. This gain compensates for the
nominal gain error of the current channel, including the current
transformer and burden resistors. If multipoint phase and gain
compensation is enabled, an additional current gain value is
applied in based on the xIRMS value to compensate for the
current transformer gain shift over input signal amplitude.
If multipoint gain and phase compensation is enabled, with
MTEN = 1, an additional gain factor, xIGAIN0 through xIGAIN5,
is applied based on the xIRMS current rms amplitude and the
MTTHR_Lx and MTTHR_Hx register values, as shown in
Figure 15.
Similarly, for the phase compensation, if multipoint phase and
gain compensation is enabled, the applied current channel phase
compensation varies based on the xIRMS input signal level.
OUTPUT
VOLTAGE
OUTPUT
CURRENT
ADE9000
60
 
= × ° = °
360 2 7 .
 
 
8000
ADE9000 Technical Reference Manual
GAIN,
PHASE
CORRECTION
xIGAIN0
xPHCAL0
X
MTTHR_L0 MTTHR_L1
= 0 MTTHR_H0
REGION0
Figure 15. Multipoint Phase and Gain Calibration
The MTTHR_Lx and MTTHR_Hx registers set up the ranges
in which to apply each set of corrections, allowing hysteresis.
The decision of which coefficients to apply is done according to
the following rules:
If xIRMS >MTTHR_H[current_region]
If current_region <=3
Else If xIRMS >MTTHR_L[current_region]
If current_region >=1
xIGAIN = xIGAIN[current_region];
xPHCAL = xPHCAL[current_region];
For example, if AIRMS goes above MTTHR_H2, the phase and
gain correction is set to AIGAIN3 and APHCAL3, respectively.
Then, if AIRMS goes below MTTHR_L3, the phase and gain
correction is set to AIGAIN2 and APHCAL2, respectively.
For proper operation, the value of the registers must be
MTTHR_L[0] < MTTHR_L[1] < MTTHR_H[0] <
MTTHR_L[2] < MTTHR_H[1] < MTTHR_L[3] <
MTTHR_H[2] < MTTHR_L[4] < MTTHR_H[3] <
MTTHR_H[4].
Multipoint phase and gain calibration is disabled by default. To
enable it, set the MTEN bit in the CONFIG0 register.
Single Point Gain and Phase
When multipoint phase and gain calibration is disabled, single-
point phase and gain calibration is allowed.
In this case, the xIGAIN register is applied. No additional
current channel gain is applied based on xIRMS amplitude.
When multipoint phase and gain calibration is disabled, the
xPHCAL0 phase compensation is always applied regardless of
the xIRMS value.
Rev. 0 | Page 12 of 86
xIGAIN4
xPHCAL4
xIGAIN3
xIGAIN2
xPHCAL3
xIGAIN1
xPHCAL2
X
xPHCAL1
X
X
, MTTHR_L2 , MTTHR_L3 , MTTHR_L4
MTTHR_H1 MTTHR_H2 MTTHR_H3
REGION1 REGION2 REGION3
Current_region++;
current_region--;
X
, MTTHR_H4 =
FULL SCALE
REGION4