ade7518 Analog Devices, Inc., ade7518 Datasheet - Page 20

• Manufacturer Part Number: ade7518
• Description: Single-phase Energy Measurement Ic With 8052 Mcu, Rtc, And Lcd Driver
• Manufacturer: Analog Devices, Inc.

ADE7518
TERMINOLOGY
Measurement Error
The error associated with the energy measurement made by the
ADE7518 is defined by the following formula:
Phase Error Between Channels
The digital integrator and the high-pass filter (HPF) in the current
channel have a nonideal phase response. To offset this phase
response and equalize the phase response between channels,
two phase correction networks are placed in the current channel:
one for the digital integrator and the other for the HPF. The
phase correction networks correct the phase response of the
corresponding component and ensure a phase match between
current channel and voltage channel to within ±0.1° over a
range of 45 Hz to 65 Hz with the digital integrator off. With
the digital integrator on, the phase is corrected to within ±0.4°
over a range of 45 Hz to 65 Hz.
Power Supply Rejection (PSR)
PSR quantifies the ADE7518 measurement error as a percentage
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 (100 mV rms/120 Hz) signal is introduced onto the
supplies. Any error introduced by this ac signal is expressed as a
percentage of reading (see the Measurement Error definition).
Percentage Error =
⎛
⎜
⎜
⎝
Energy
Register
True
Energy
−
True
Energy
⎞
⎟
⎟
⎠
×
100
%
Rev. 0 | Page 20 of 128
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 supplies are varied ±5%. Any error
introduced is again expressed as a percentage of the reading.
ADC Offset Error
ADC offset error is 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 HPF1 is switched on, the offset is
removed from the current channel, and the power calculation
is not affected by this offset. The offsets can be removed by
performing an offset calibration (see the Analog Inputs section).
Gain Error
Gain error is 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). It is measured for each of the gain settings on the
current channel (1, 2, 4, 8, and 16). The difference is expressed
as a percentage of the ideal code.