ADE7761B
TERMINOLOGY
For the dc PSR measurement, a reading at nominal supplies (5 V)
is taken. A second reading is obtained with the same input signal
levels when the power supplies are varied 5%. Any error
introduced is again expressed as a percentage of reading.
Measurement Error
The error associated with the energy measurement made by the
ADE7761B is defined by
Percentage Error =
ADC Offset Error
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Energy Registered by ADE7761B −True Energy
This is the dc offset associated with the analog inputs to the ADCs.
With the analog inputs connected to AGND, the ADCs still see
a dc analog input signal. The magnitude of the offset depends on
the input gain and range selection (see the Typical Performance
Characteristics section). However, when HPFs are switched on,
the offset is removed from the current channels and the power
calculation is not affected by this offset.
× 100%
True Energy
Phase Error Between Channels
The high-pass filter (HPF) in the current channel has a phase
lead response. To offset this phase response and equalize the
phase response among channels, a phase correction network is
also placed in the current channel. The phase correction network
ensures a phase match between the current channels and the
voltage channels to within 0.1° over a range of 45 Hz to
65 Hz and 0.2° over a range of 40 Hz to 1 kHz.
Gain Error
The gain error in the ADE7761B ADCs is defined as the difference
between the measured output frequency (minus the offset) and
the ideal output frequency. It is measured with a gain of 1 in
Channel V1A. The difference is expressed as a percentage of the
ideal frequency, which is obtained from the transfer function
(see the Transfer Function section).
Power Supply Rejection (PSR)
PSR quantifies the ADE7761B measurement error as a percentage
of reading when the power supplies are varied. For the ac PSR
measurement, a reading at nominal supplies (5 V) is taken.
A second reading is obtained with the same input signal levels
when an ac signal (175 mV rms/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).
Gain Error Match
The gain error match is defined as the gain error (minus the offset)
obtained when switching between a gain of 1 or 16. It is expressed
as a percentage of the output ADC code obtained under a gain of 1.
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