SA2102D
sames
p(t)
= VM IM sin(wt +q )sin(wt +y )
FUNCTIONAL DESCRIPTION
The SA2102D is a CMOS integrated circuit, which performs
power/energy calculations across a dynamic range of 1000:1
to an accuracy that exceeds the IEC 61036 Class 1
specification.
= VM IM sin(wt +q )sin(wt +q -j)
VRMS IRMS [cosj - cos(2(wt +q ) -j)]
=
where v(t) is the instantaneous voltage
i(t) is the instantaneous current,
The integrated circuit includes all the required functions for
single phase power and energy measurement. Two A/D
converters sample the voltage and current inputs. The
calculations required for power and energy are performed and
pulses on the LED, MON and MOP outputs represent the
results.
VM is the maximum amplitude of the voltage signal,
IM is the maximum amplitude of the current signal,
is the voltage phase angle,
q
y is the current phase angle and
= 100Hz noise component
VI cos(2(wt +q ) -j)
on a 50Hz mains system.
This power information is then integrated over time to provide
the average power information.
Internal offsets are eliminated through the use of cancellation
techniques. The SA2102D generates pulses at a frequency
that is proportional to the power consumption. Complimentary
output pins MOP and MON are provided for driving a stepper
motor. A MOP pulse followed immediately by a MON pulse
represents an energy pulse. This minimizes the risk of (after
power up) losing the first energy pulse as a result of the stepper
motor residing in the wrong phase.
1 T
Average Power (P)
=
=
p(t)dt
T ò
0
VRMS IRMS cosj
Where p(t) is the instantaneous power and
jis the power factor.
cos
ANALOG INPUT CONFIGURATION
The input circuitry of the current and voltage sensor inputs is
illustrated in figure 5.
The LED output is normally proportional to the average power
consumption measured. When in FAST mode, the LED output
is proportional to the instantaneous active power consumption.
The FAST mode is intended for meter calibration purposes.
V
DD
The two A/D converters convert the signals on the voltage and
current sense inputs to a digital format for further processing.
The current sense inputs (IIP and IIN) are identical and
balanced. A input signal with a range of 1:1000 is measured at
these inputs.
IIP
V
V
SS
DD
CURRENT
SENSOR
INPUTS
AI
An integrated anti-creep function prevents any output pulses if
the measured power is less than 0.02% of the meters rated
current.
IIN
V
SS
The two digital signals, accurately representing the current and
voltage inputs, are multiplied using digital multiplication. The
output of the multiplier is the instantaneous power.
For voltage and current in phase instantaneous power is
calculated by:
V
DD
IVP
v(t)´i(t)
Instantaneous power p(t)
=
VOLTAGE
SENSOR
INPUT
V
SS
A V
=
VM sin(wt +q)´IM sin(wt +y)
IM
VM
IRMS
,
=
j =q -y
let
, VRMS
=
2
2
GND
DR-01148
Figure 5: Analog input configuration
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