ADE7880 View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'ADE7880' PDF : 104 Pages View PDF
ADE7880
TERMINOLOGY
Measurement Error
The error associated with the energy measurement made by the
ADE7880 is defined by
Measurement Error =
Energy Registered by ADE7880 True Energy 100% (1)
True Energy
Power Supply Rejection (PSR)
This quantifies the ADE7880 measurement error as a percen-
tage of reading when the power supplies are varied. For the ac
PSR measurement, a reading at nominal supplies (3.3 V) is
taken. A second reading is obtained with the same input signal
levels when an ac signal (120 mV rms at 100 Hz) is introduced
onto the supplies. Any error introduced by this ac signal is
expressed as a percentage of reading (see the Measurement
Error definition).
For the dc PSR measurement, a reading at nominal supplies
(3.3 V) is taken. A second reading is obtained with the same
input signal levels when the power supplies are varied ±10%.
Any error introduced is expressed as a percentage of the
reading.
ADC Offset
ADC offset refers to the dc offset associated with the analog
inputs to the ADCs. It means that with the analog inputs
connected to AGND, the ADCs still see a dc analog input
signal. The magnitude of the offset depends on the gain and
input range selection. The high-pass filter (HPF) removes the
offset from the current and voltage channels; therefore, the
power calculation remains unaffected by this offset.
Gain Error
The gain error in the ADCs of the ADE7880 is defined as the
difference between the measured ADC output code (minus the
offset) and the ideal output code (see the Current Channel ADC
section and the Voltage Channel ADC section). The difference
is expressed as a percentage of the ideal code.
CF Jitter
The period of pulses at one of the CF1, CF2, or CF3 pins is
continuously measured. The maximum, minimum, and average
values of four consecutive pulses are computed as follows:
Data Sheet
Maximum = max(Period0, Period1, Period2, Period3)
Minimum = min(Period0, Period1, Period2, Period3)
Average = Period0 Period1 Period2 Period3
4
The CF jitter is then computed as
CFJITTER
Maximum Minimum100%
Average
(2)
Signal-to-Noise Ratio (SNR)
SNR is the ratio of the rms value of the actual input signal to the
rms sum of all other spectral components below 3.3 kHz, excluding
harmonics and dc. The input signal contains only the fundamental
component. The spectral components are calculated over a 2 sec
window. The value for SNR is expressed in decibels.
Signal-to-Noise-and-Distortion (SINAD) Ratio
SINAD is the ratio of the rms value of the actual input signal to the
rms sum of all other spectral components below 3.3 kHz,
including harmonics but excluding dc. The input signal contains
only the fundamental component. The spectral components are
calculated over a 2 sec window. The value for SINAD is expressed
in decibels.
Harmonic Power Measurement Error
To measure the error in the harmonic active and reactive power
calculations made by the ADE7880, the voltage channel is supplied
with a signal comprising a fundamental and one harmonic
component with amplitudes equal to 250 mV. The current
channel is supplied with a signal comprising a fundamental
with amplitude of 50 mV and one harmonic component of the
same index as the one in the voltage channel. The amplitude of
the harmonic is varied from 250 mV, down to 250 μV, 2000 times
lower than full scale.
The error is defined by
Measurement Error =
Power Registered by ADE7880 TruePower
100% (3)
True Power
Rev. C | Page 20 of 107
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