ADE7758_15 datasheet(42/72 Pages) AD

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ADE7758

Data Sheet

Rev. E | Page 42 of 72

CALIBRATION

A reference meter or an accurate source is required to calibrate

the ADE7758 energy meter. When using a reference meter, the

ADE7758 calibration output frequencies APCF and VARCF are

adjusted to match the frequency output of the reference meter

under the same load conditions. Each phase must be calibrated

separately in this case. When using an accurate source for

calibration, one can take advantage of the line cycle accumulation

mode and calibrate the three phases simultaneously.

There are two objectives in calibrating the meter: to establish

the correct impulses/kW-hr constant on the pulse output and to

obtain a constant that relates the LSBs in the energy and rms

registers to Watt/VA/VAR hours, amps, or volts. Additionally,

calibration compensates for part-to-part variation in the meter

design as well as phase shifts and offsets due to the current

sensor and/or input networks.

Calibration Using Pulse Output

The ADE7758 provides a pulsed output proportional to the

active power accumulated by all three phases, called APCF.

Additionally, the VARCF output is proportional to either the

reactive energy or apparent energy accumulated by all three

phases. The following section describes how to calibrate the

gain, offset, and phase angle using the pulsed output information.

The equations are based on the pulse output from the ADE7758

(APCF or VARCF) and the pulse output of the reference meter

or CFEXPECTED.

Figure 77 shows a flowchart of how to calibrate the ADE7758

using the pulse output. Because the pulse outputs are proportional

to the total energy in all three phases, each phase must be calibrated

individually. Writing to the registers is fast to reconfigure the part

for calibrating a different phase; therefore, Figure 77 shows a

method that calibrates all phases at a given test condition before

changing the test condition.

ADE7758 Datasheet(PDF) 42 Page - Analog Devices