SA2002P
sames
creep threshold. The creep threshold is implemented to
prevent the meter from accumulating energy when no load is
connected.
be programmed. During the Kr calculation the value was
rounded up and any rounding error is now taken into account. A
ratio of the rounding "error" is calculated relative to the center
of the variable range of Cor (481 - 512).
Corr = 495 x (1 + (Krx - (Kr + 1)) / Krx)
Corr = 495 x (1 + (39.61549 - 40) / 39.61549)
Corr = 495 x 0.990294
Cs is made up of bit 0 of byte D14.
D14[0]
Creep threshold
0
1
0.02% of rated current
0.01% of rated current
Corr = 490.1955
Corr = 490 (Convert to Integer)
Cor = Corr -1
Cor = 489
Metering direction select (Ds)
The SA2002P may be configured to measure positive energy
or positive and negative energy.
Store the calculated values in the EEPROM
Ensure that the device reload its registers from the EEPROM
by means of the RLOAD pin or power down the meter and
power up again.
Ds is made up of bit 2 of byte D14.
D14[2]
Metering direction select
0
1
Bi-directional energy measurement
Positive energy measurement
The meter is now set up with the correct register values but not
yet calibrated.
DC or AC measurement mode (Dc)
The following example shows how to calibrate the meter
The SA2002P may be configured to measure AC energy or DC
energy. In case of AC measurement selection, the device will
track the mains frequency for offset cancellation purposes. In
DC measurement mode the device is locked to a fixed
frequency for offset cancellation. The FMO output is switched
to 28Hz in DC mode.
Measure the %Error with a Watt hour standard
%Error =(Measured Energy - Real Energy)/Real Energy x 100
The %Error will be worked back into the calculations above.
For this example we will assume a 2.83% error between the
correct energy value and energy measured by the SA2002P.
Dc is made up of bit 3 of byte D14.
D14[3]
Recalculate the Kr value
DC or AC measurement mode
AC measurement mode
Krx = 641454 / Unom / Imax / M x 3600 x 1000 / 495 x (1 +
0
1
%Error / 100 )
DC measurement mode
Krx = 641454 / 230 / 80 / 6400 x 3600 x 1000 / 495 x 1.0283
Krx = 40.73661
Example of calculating Kr and Cor values
Krx = 41 (Round up and make integer value)
Metering specifications:
Kr = Krx-1
Unom
=
=
=
230V
Kr = 41-1
Imax
80A
Kr = 40
Meter constant
6400 p/kWh
The value 40 is stored in the Kr.
Calculate the Kr value:
The Cor value must be recalculated.
Corr = 495 x (1 + (Krx - (Kr + 1)) / Krx)
Corr = 495 x (1 + (40.7366 - 41) / 40.7366
Corr = 495 x 0.993534
Krx = 641454 / Unom / Imax / M x 3600x1000/495
Krx = 641454 / 230 / 80 / 6400 x 3600 x 1000 / 495
Krx = 39.61549
Krx = 40 (round Krx up to convert to integer)
Kr = Krx-1
Corr = 491.7995
Corr = 492 (Convert to Integer)
Cor = Corr-1
Kr = 39
Cor = 491
The value 39 is stored in the Kr register. The pre-divider (Cor)
value is calculated next. Cor is programmable to divide
between 481 and 512. Only the 5 least significant bits need to
Store the calculated values in the EEPROM and the meter is
calibrated.
9/14
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