ANALOG DEVICES AN-1152 Service Manual

AN-1152

APPLICATION NOTE

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Calibrating a Single-Phase Energy Meter Based on the ADE7816

by Aileen Ritchie

INTRODUCTION

This application note describes how to calibrate the ADE7816.
It details the calibration procedure, including equations and
examples of how to calculate each constant.

The ADE7816 is a high accuracy multichannel metering IC that
allows the energy to be measured on up to six current channels.

It provides a variety of energy measurements including active
and reactive energy, along with current and voltage rms readings.
A variety of power quality features, including no load, reverse
power, and angle measurement, are also provided. The ADE7816
can be accessed via an SPI, I
(HSDC) interface.

2

C, or high speed data capture

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AN-1152 Application Note

TABLE OF CONTENTS

Introduction ...................................................................................... 1

Revision History ............................................................................... 2

Calibration Basics ............................................................................. 3

Calibration Steps ........................................................................... 3

Calibration Setup .......................................................................... 3

Required Register Settings .......................................................... 4

Energy Calibration ........................................................................... 5

Current Channel Gain Matching ............................................... 5

REVISION HISTORY

5/12—Revision 0: Initial Version

Phase Calibration ..........................................................................5

Establishing the Wh/LSB Constant—First Meter Only ...........6

Active Energy Gain Calibration ..................................................6

Reactive Energy Gain Calibration ...............................................7

Advanced Energy Offset Calibration (Optional) ......................7

Current and Voltage RMS ............................................................8

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Application Note AN-1152

Calibration Stage

Typical Requirement

VOLTAGE

THE SOURCE P ROVIDES THE

ACCURACY FOR CALIBRATION

SOURCE

CURRENT ×6

10668-001

CALIBRATION BASICS

To obtain accurate readings that do not reflect meter-to-meter
variations in external components or the internal voltage reference,
the ADE7816 requires calibration. Calibration is required on
every meter; however, it is a simple process that can be performed
quickly.

The active and reactive energies, along with current and voltage
rms, must be calibrated for accurate readings to be acquired.
All signal paths are independent and, therefore, perform the
calibration on the measurements that are required in the
completed meter.

Access to the energy metering registers is provided via the SPI

2

or I

C interface (see the ADE7816 data sheet for more details).
When calibrating the active and reactive energy readings, the
line cycle accumulation mode should be used. See the ADE7816
data sheet for details on the line cycle accumulation mode.

CALIBRATION STEPS

When designing a meter using the ADE7816, a maximum of
three calibration stages is required: gain, phase, and offset.
These stages must be performed on each measurement sepa­rately. Depending on the external configuration and meter class,
one or more of these stages can be omitted. Table 1 provides
guidance on which calibration steps are typically required for a
particular configuration. Because the requirements and perfor­mance can differ on a design-by-design basis, use Table 1 as a
general guideline only. The performance of the meter should be
evaluated to determine whether any additional calibration steps
are required.

Table 1. Typical Calibration Steps

Gain Calibration It is always required.
Phase Calibration

Offset Calibration

It is required when using a sensor that
introduces a phase delay.

If the sensor does not introduce a phase
delay, it is not typically required.

When looking for high accuracy over a
large dynamic range, it is often required.

It is not usually required for all other meter
designs.

CALIBRATION SETUP

Accurate Source

To calibrate the ADE7816, an accurate source should be used.
The accurate source must be able to provide a controllable
voltage and current input with higher accuracy than that
required in the resulting meter. Figure 1 shows a typical setup
using an accurate source.

Figure 1. Accurate Source

Ideally, calibrate all six current channels simultaneously. If this
is not possible, each channel can be calibrated individually. Care
should be taken to isolate and verify the board level channel-to­channel crosstalk for optimum performance.

Required Input Conditions

The gain and phase calibration steps can be performed with a
single set of inputs. Set the voltage to the nominal value, typi­cally 110 V or 220 V. The current should also be set to the
nominal value, for example, 10 A. It is advisable to set the
current around 10 times less than the maximum current for
the meter. The current and voltage inputs should be applied
at a power of around 0.5. The load can be either capacitive or
inductive. The key factor when setting up the calibration inputs
is to determine exactly what is being applied to the meter. For
example, there is no issue in using a power factor of 0.45 as long
as it is known that this is what is being applied to the meter.

If an offset calibration step is required, a second load must be
applied at the minimum current. The voltage should remain at
nominal level and the power factor at 0.5.

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AN-1152 Application Note

0x43B1

PCF_A_COEFF

Phase calibration for Current Channel A

0x400CA4 (50 Hz)

0x4388

DICOEFF

Digital integrator algorithm; required only if using di/dt sensors

0xFFF8000

REQUIRED REGISTER SETTINGS

Prior to calibrating the ADE7816, it is important that a set of
default registers be configured. These registers are listed in

Table 2. Default Registers Required Prior to Calibration

Register Address Register Name Register Description Required Value

0x43AB WTHR1 Threshold register for active energy 0x000002
0x43AC WTHR0 Threshold register for active energy 0x000000
0x43AD VARTHR1 Threshold register for reactive energy 0x000002
0x43AE VARTHR0 Threshold register for reactive energy 0x000000

0x43B2 PCF_B_COEFF Phase calibration for Current Channel B 0x400CA4 (50 Hz)
0x43B3 PCF_C_COEFF Phase calibration for Current Channel C 0x400CA4 (50 Hz)
0x43B4 PCF_D_COEFF Phase calibration for Current Channel D 0x400CA4 (50 Hz)
0x43B5 PCF_E_COEFF Phase calibration for Current Channel E 0x400CA4 (50 Hz)
0x43B6 PCF_F_COEFF Phase calibration for Current Channel F 0x400CA4 (50 Hz)

Tabl e 2. Refer to the ADE7816 data sheet for details on these
registers.

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