ADE5166_08 AD [Analog Devices], ADE5166_08 Datasheet - Page 55

• Manufacturer Part Number: ADE5166_08
• Description: Single-Phase Energy Measurement IC with 8052 MCU, RTC, and LCD Driver
• Manufacturer: AD [Analog Devices]

ACTIVE ENERGY CALCULATION
As stated in the Active Power Calculation section, power is
defined as the rate of energy flow. This relationship can be
expressed mathematically, as shown in Equation 11.
where:
P is power.
E is energy.
Conversely, energy is given as the integral of power.
The ADE5166/ADE5169 achieve the integration of the active
power signal by continuously accumulating the active power signal
in an internal, nonreadable, 49-bit energy register. The register
(WATTHR[23:0], Address 0x01) represents the upper 24 bits
of this internal register. This discrete time accumulation or
summation is equivalent to integration in continuous time.
Equation 13 expresses the relationship.
where:
n is the discrete time sample number.
T is the sample period.
The discrete time sample period (T) for the accumulation
register in the ADE5166/ADE5169 is 1.22 μs (5/MCLK). In
addition to calculating the energy, this integration removes any
sinusoidal components that may be in the active power signal.
Figure 61 shows this discrete time integration or accumulation.
The active power signal in the waveform register is continuously
added to the internal active energy register.
E
E
P =
=
=
∫
∫
dE
p
dt
P
) (
t
) (
t
dt
CHANNEL
CURRENT
CHANNEL
VOLTAGE
dt
=
lim
t
→
0
⎧
⎨
⎩
n
∑
∞
=
1
p
(
nT
T
)
×
T
⎫
⎬
⎭
ACTIVE POWER
LPF2
MCLK
sgn
SIGNAL
5
TIME (nT)
WATTOS[15:0]
2
6
2
+
5
+
WAVEFORM
2
REGISTER
–6
VALUES
2
–7
Figure 61. Active Energy Calculation
2
–8
FOR WAVEFORM
SAMPLING
WGAIN[11:0]
Rev. 0 | Page 55 of 148
(11)
(12)
(13)
WDIV[7:0]
%
The active energy accumulation depends on the setting of
POAM (Bit 1) and ABSAM (Bit 0) in the ACCMODE register
(Address 0x0F). When both bits are cleared, the addition is signed
and, therefore, negative energy is subtracted from the active
energy contents. When both bits are set, the ADE5166/ADE5169
are set to be in the more restrictive mode, the positive-only
accumulation mode.
When POAM (Bit 1) in the ACCMODE register (Address 0x0F)
is set, only positive power contributes to the active energy accumu-
lation. When ABSAM (Bit 0) in the ACCMODE register
(Address 0x0F) is set, the absolute active power is used for the
active energy accumulation (see the Watt-Absolute Accumulation
Mode section).
The output of the multiplier is divided by the value in the WDIV
register (Address 0x24). If the value in the WDIV register is equal
to 0, the internal active energy register is divided by 1. WDIV is an
8-bit, unsigned register. After dividing by WDIV, the active energy
is accumulated in a 49-bit internal energy accumulation register.
The upper 24 bits of this register are accessible through a read
to the active energy register (WATTHR[23:0], Address 0x01).
A read to the RWATTHR register (Address 0x02) returns the
contents of the WATTHR register, and the upper 24 bits of the
internal register are cleared. As shown in Figure 61, the active
power signal is accumulated in an internal 49-bit signed register.
The active power signal can be read from the waveform register
by setting the WAVMODE register (Address 0x0D) and setting
the WFSM bit (Bit 5) in the Interrupt Enable 3 SFR (MIRQENH,
Address 0xDB). Like the current and voltage channels waveform
sampling modes, the waveform data is available at sample rates of
25.6 kSPS, 12.8 kSPS, 6.4 kSPS, and 3.2 kSPS.
TO
DIGITAL-TO-FREQUENCY
CONVERTER
+
+
48
23
WATTHR[23:0]
OUTPUTS FROM THE LPF2 ARE
ACCUMULATED (INTEGRATED) IN
THE INTERNAL ACTIVE ENERGY REGISTER
0
UPPER 24 BITS ARE
ACCESSIBLE THROUGH
WATTHR[23:0] REGISTER
ADE5166/ADE5169
0