ADE7758 Analog Devices, ADE7758 Datasheet - Page 12

• Manufacturer Part Number: ADE7758
• Description: Poly Phase Multifunction Energy Metering IC with Per Phase Information
• Manufacturer: Analog Devices

ADE7758
TERMINOLOGY
Measurement Error
The error associated with the energy measurement made by the
ADE7758 is defined by the following formula
Phase Error between Channels
The high-pass filter and digital integrator introduce a slight
phase mismatch between the current and the voltage channel.
The all-digital design ensures that the phase matching between
the current channels and voltage channels in all three phases is
within ±0.1° over a range of 45 Hz to 65 Hz and ±0.2° over a
range of 40 Hz to 1 kHz. This internal phase mismatch can be
combined with the external phase error (from current sensor or
component tolerance) and calibrated with the phase calibration
registers.
Power Supply Rejection
This quantifies the ADE7758 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.
Measuremen
Energy
Registered
t
Error
True
by
=
ADE7758
Energy
–
True
Energy
×
100
%
Rev. A | Page 12 of 68
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 the reading.
ADC Offset Error
This 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 (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.
Gain Error
The gain error in the ADCs of the ADE7758 is defined as the
difference between the measured ADC output code (minus the
offset) and the ideal output code (see the Current Channel ADC
and Voltage Channel ADC sections). The difference is
expressed as a percentage of the ideal code.
Gain Error Match
The gain error match is defined as the gain error (minus the
offset) obtained when switching between a gain of 1, 2, or 4. It is
expressed as a percentage of the output ADC code obtained
under a gain of 1.