ADE7169ASTF16 datasheet(53/140 Pages) AD

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Preliminary Technical Data

ADE7169F16

Rev. PrD | Page 53 of 140

The ADE7169F16 includes a no-load threshold feature on the

active energy that eliminates any creep effects in the meter. The

ADE7169F16 accomplishes this by not accumulating energy if

the multiplier output is below the no-load threshold. When the

active power is below the no-load threshold, the APNOLOAD

flag in the Interrupt Status Register 1 SFR (MIRQSTL, 0xDC) is

set. If the APNOLOAD bit is set in the Interrupt Enable

ADE interrupt. The ADE interrupt stays active until the

APNOLOAD status bit is cleared—see Energy measurement

interrupts section.

The No-load threshold level is selectable by setting bits

APNOLOAD in the NLMODE register (0x0E). Setting these

bits to 0b00 disable the no-load detection and setting them to

0b01, 0b10 or 0b11 set the no-load detection threshold to

0.015%, 0.0075% and 0.0037% of the full-scale output frequency

of the multiplier respectively. The IEC62053-21 specification,

states that the meter must start up with a load equal to or less

than 0.4% Ib. If the nominal voltage input and the maximum

current represent 50% of the full scale ADC input and Imax =

400% of Ib, the ADE7169F16 no-load threshold options

translate to 0.24% of Ib, 0.12% of Ib and 0.06% of Ib

respectively.

WGAIN[11:0]

WDIV[7:0]

LPF2

CURRENT

CHANNEL

VOLTAGE

CHANNEL

TIME (nT)

CLKIN

ACTIVE POWER

SIGNAL

WATTHR[23:0]

OUTPUTS FROM THE LPF2 ARE

ACCUMULATED (INTEGRATED) IN

THE INTERNAL ACTIVE ENERGY REGISTER

UPPER 24 BITS ARE

ACCESSIBLE THROUGH

WATTHR[23:0] REGISTER

WAVEFORM

VALUES

WATTOS[15:0]

sgn

2-6 2-7 2-8

FOR WAVEF0RM

SAMPLING

DIGITAL TO FREQUENCY

CONVERTER

Figure 39. ADE7169F16 Active Energy Calculation

Active Energy Calculation

As stated earlier, power is defined as the rate of energy flow.

This relationship can be expressed mathematically in Equation 12.

(12)

where:

P is power.

E is energy.

Conversely, energy is given as the integral of power.

∫

= Pdt

(13)

The ADE7169F16 achieves the integration of the active power

signal by continuously accumulating the active power signal in

an internal non-readable 49-bit energy register. The active

energy register (WATTHR[23:0]) represents the upper 24 bits of

this internal register. This discrete time accumulation or

summation is equivalent to integration in continuous time.

Equation 14 expresses the relationship.

()

(

)

p t dt

Lim

p nT

∞

→

⎧⎫

⎨⎬

⎩

⎭

∑

∫

(14)

where:

n is the discrete time sample number.

T is the sample period.

The discrete time sample period (T) for the accumulation

calculating the energy, this integration removes any sinusoidal

components that might be in the active power signal. Figure 39

shows this discrete time integration or accumulation. The active

power signal in the waveform register is continuously added to

the internal active energy register.

ADE7169ASTF16 数据表(PDF) 53 Page - Analog Devices

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