ADE7166 datasheet(51/144 Pages) AD

51 / 144 page

ADE7566/ADE7569/ADE7166/ADE7169

Rev. A | Page 51 of 144

Calibration Concerns

Typically, when a meter is being calibrated, the voltage and

current circuits are separated, as shown in Figure 48. This

means that current passes through only the phase or neutral

circuit. Figure 48 shows current being passed through the phase

circuit. This is the preferred option because the ADE7166/

ADE7169 start billing on the input IPA on power-up. The phase

circuit CT is connected to IPA in the diagram. Because the

current sensors are not perfectly matched, it is important to

match current inputs. The ADE7166/ADE7169 provide a gain

calibration register for IPB, IBGAIN (address 0x1C). IBGAIN is a

12-bit, signed, twos complement register that provides a gain

resolution of 0.0244%/LSB.

For calibration, a first measurement should be done on IPA by

setting the SEL_I_CH bits to 0b01 in the CALMODE Register

(0x3D). This measurement should be compared to the

measurement on IPB. Measuring IPB can be forced by setting

SEL_I_CH bits to 0b10 in the CALMODE Register (0x3D). The

gain error between these two measurements can be evaluated using

()

( )

()

Measuremen

Error

−

The two channels IPA and IPB can then be matched by writing

–Error(%)/(1 + Error (%)) × 212 to the IBGAIN register. This

matching adjustment is be valid for all energy measurements,

active power, reactive power, Irms, and apparent power, made by

the ADE7166/ADE7169.

AGND

IPB

IPA

IPB

TEST

CURRENT

240V rms

Figure 48. Fault Conditions for Inactive Input Greater Than Active Input

di/dt CURRENT SENSOR AND DIGITAL

INTEGRATOR FOR THE ADE7569/ADE7169

A di/dt sensor, a feature available for the AD7569/ADE7169 but

not for the AD7566/ADE7166, detects changes in the magnetic

field caused by ac currents. Figure 49 shows the principle of a

di/dt current sensor.

MAGNETIC FIELD CREATED BY CURRENT

(DIRECTLY PROPORTIONAL TO CURRENT)

+ EMF (ELECTROMOTIVE FORCE)

– INDUCED BY CHANGES IN

MAGNETIC FLUX DENSITY (di/dt)

Figure 49. Principle of a di/dt Current Sensor

The flux density of a magnetic field induced by a current is

directly proportional to the magnitude of the current. The

changes in the magnetic flux density passing through a conductor

loop generate an electromotive force (EMF) between the two

ends of the loop. The EMF is a voltage signal that is proportional

to the di/dt of the current. The voltage output from the di/dt

current sensor is determined by the mutual inductance between

the current-carrying conductor and the di/dt sensor. The current

signal needs to be recovered from the di/dt signal before it can

be used. An integrator is therefore necessary to restore the

signal to its original form.

The ADE7569/ADE7169 have a built-in digital integrator to

recover the current signal from the di/dt sensor. The digital

integrator on the current channel is switched off by default when

the ADE7569/ADE7169 are powered up. Setting the INTE bit in

the MODE1 register (0x0B) turns on the integrator. Figure 50 to

Figure 53 show the magnitude and phase response of the digital

integrator.

FREQUENCY (Hz)

–10

–20

–30

–40

–50

100

1000

Figure 50. Combined Gain Response of the Digital Integrator and

Phase Compensator

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