Datasheet ADE7761B (Analog Devices) - 10

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ADE7761B TERMINOLOGY Measurement Error
For the dc PSR measurement, a reading at nominal supplies (5 V) The error associated with the energy measurement made by the is taken. A second reading is obtained with the same input signal ADE7761B is defined by levels when the power supplies are varied ±5%. Any error introduced is again expressed as a percentage of reading. Percentage Error =
ADC Offset Error
⎛ Energy Registered by ADE7761B −True Energy ⎞ ⎜ ⎟ × 100% This is the dc offset associated with the analog inputs to the ADCs. ⎜ ⎟ ⎝ True Energy ⎠ With the analog inputs connected to AGND, the ADCs still see a dc analog input signal. The magnitude of the offset depends on
Phase Error Between Channels
the input gain and range selection (see the Typical Performance The high-pass filter (HPF) in the current channel has a phase Characteristics section). However, when HPFs are switched on, lead response. To offset this phase response and equalize the the offset is removed from the current channels and the power phase response among channels, a phase correction network is calculation is not affected by this offset. also placed in the current channel. The phase correction network ensures a phase match between the current channels and the
Gain Error
voltage channels to within ±0.1° over a range of 45 Hz to The gain error in the ADE7761B ADCs is defined as the difference 65 Hz and ±0.2° over a range of 40 Hz to 1 kHz. between the measured output frequency (minus the offset) and the ideal output frequency. It is measured with a gain of 1 in
Power Supply Rejection (PSR)
Channel V1A. The difference is expressed as a percentage of the PSR quantifies the ADE7761B measurement error as a percentage ideal frequency, which is obtained from the transfer function of reading when the power supplies are varied. For the ac PSR (see the Transfer Function section). measurement, a reading at nominal supplies (5 V) is taken. A second reading is obtained with the same input signal levels
Gain Error Match
when an ac signal (175 mV rms/100 Hz) is introduced onto the The gain error match is defined as the gain error (minus the offset) supplies. Any error introduced by this ac signal is expressed as obtained when switching between a gain of 1 or 16. It is expressed a percentage of reading (see the Measurement Error definition). as a percentage of the output ADC code obtained under a gain of 1. Rev. 0 | Page 10 of 24 Document Outline FEATURES GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS TIMING CHARACTERISTICS Timing Diagram ABSOLUTE MAXIMUM RATINGS PERFORMANCE ISSUES THAT MAY AFFECT BILLING ACCURACY Case 1 Case 2 ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS TEST CIRCUIT TERMINOLOGY THEORY OF OPERATION POWER SUPPLY MONITOR ANALOG INPUTS Channel V1 (Current Channel) Channel V2 (Voltage Channel) MISCAL Input Typical Connection Diagrams INTERNAL OSCILLATOR ANALOG-TO-DIGITAL CONVERSION Antialias Filter ACTIVE POWER CALCULATION Power Factor Considerations Nonsinusoidal Voltage and Current HPF and Offset Effects DIGITAL-TO-FREQUENCY CONVERSION TRANSFER FUNCTION Frequency Output F1 and Frequency Output F2 Frequency Output CF FAULT DETECTION Fault with Active Input Greater Than Inactive Input Fault with Inactive Input Greater Than Active Input Calibration Concerns MISSING NEUTRAL MODE Important Note for Billing of Active Energy Missing Neutral Detection Missing Neutral Gain Calibration APPLICATIONS INFORMATION INTERFACING TO A MICROCONTROLLER FOR ENERGY MEASUREMENT SELECTING A FREQUENCY FOR AN ENERGY METER APPLICATION Frequency Outputs No-Load Threshold NEGATIVE POWER INFORMATION OUTLINE DIMENSIONS ORDERING GUIDE