ADE7758ARWRL datasheet(47/68 Pages) AD

47 / 68 page

ADE7758

Rev. A | Page 47 of 68

Example—Offset Calibration of Phase a Using Pulse Output

For this example, ITEST = 50 mA, VNOM = 220 V, VFULLSCALE = 500

V, IFULLSCALE = 130 A, MC = 3200 impulses/kWh, Power Factor =

1, Frequency = 50 Hz, and CLKIN = 10 MHz.

With ITEST, VNOM, and unity power factor, the example ADE7758

meter shows 0.009773 Hz on the APCF pulse output and

0.009773 Hz on the VARCF pulse output. This is equivalent to

0.24% for the watt measurement and 0.24% for the VAR

measurement. Using Equations 38 through 41, the values 0xFFB

and 0xFFA should be written to AWATTOS (0x39) and VAROS

(0x3C), respectively.

For AWATTOS:

0186

For AVAROS:

014

2083

202

()

–

227

0186

00975

0024

–

AWATTOS

()

–

227

014

00975

0024

–

AVAROS

Calibration Using Line Accumulation

Line cycle accumulation mode configures the nine energy

registers such that the amount of energy accumulated over an

integer number of half line cycles appears in the registers after

the LINECYC interrupt. The benefit of using this mode is that

the sinusoidal component of the active energy is eliminated.

Figure 80 shows a flow chart of how to calibrate the ADE7758

using the line accumulation mode. Calibration of all phases and

energies can be done simultaneously using this mode to save

time during calibration.

START

CAL IRMS OFFSET

CAL VRMS OFFSET

CAL WATT AND VA

GAIN ALL PHASES

@ PF = 1

CAL VAR GAIN ALL

PHASES @ PF = 0

CALIBRATE PHASE

ALL PHASES

@ PF = 0.5

CALIBRATE ALL

PHASES WATT

OFFSET @ IMIN AND

PF = 1

CALIBRATE ALL

PHASES VAR

OFFSETS @ IMIN

AND PF = 0

END

Figure 80. Calibration Using Line Accumulation

Gain Calibration Using Line Accumulation

Gain calibration is used for meter-to-meter gain adjustment,

APCF or VARCF output rate calibration, and determining the

Wh/LSB, VARh/LSB, and VAh/LSB constant.

Step 0: Before performing the gain calibration, the

CFNUM/CFDEN (0x45/0x46) and VARCFNUM/VARCFDEN

(0x47/0x48) values can be set to achieve the correct

impulses/kWh, impulses/kVAh, or impulses/kVARh using the

same method outlined in Step 4 in the Gain Calibration Using

Pulse Output section. The calibration of xWG/xVARG/xVAG

(0x2A through 0x32) is done with the line accumulation mode.

Figure 81 shows the steps involved in calibrating the gain

registers using the line accumulation mode.

ADE7758ARWRL Datasheet(PDF) 47 Page - Analog Devices

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