SA2005P
ssaammeess
Programmable adder mode (SUM)
The SA2005P can be programmed to sum the energy
measurement as follows:
Calculate the Channel balance values:
During the rated conditions calculation the rated condition
register was rounded and any rounding errors is now taken
into account:
Total sum
This represents the total sum of the energy measured on all
three phases flowing through the current sensors. Negative
energy flow is taken into consideration.
Gain = ((Krx - Kr+1 ) / Krx) x 100
Gain = ((38.3327 - 38) / 38.337) x 100
Gain = 0.8679
Energy = Energy phase 1 + Energy Phase 2 + Energy
Phase 3
The real channel balance errors still need to be measured so
CHB1,CHB2, CHB3 and CBMIN are set to 0 for all phases.
Absolute sum
This represents the sum of the energy measured on all three
phases, regardless of the direction of energy flow through
the current sensors.
Calculate the Pre-divider values:
Cb1 = (CHB1 - CBMIN + Gain ) x 256 / 100
Cb1 = (0% - 0% + Gain ) x 256 / 100
Cb1 = Gain x 256 / 100
Cb1 = 0.8679 x 256 / 100
Cb1 =2.2218
Power = abs (Energy phase 1) + abs (Energy phase 2) +
abs (Energy phase 3)
During calibration the device may be programmed to use only
a specific phase for energy measurement. This can be used for
channel balancing.
Convert to integer
Cb1 = 2
D16[2] D16[1] D16[0] Counter Resolution
At this stage all three channels will be set with the same
values, Cb1= Cb2= Cb3. Store the calculated values in the
EEPROM. Ensure that the SA2005P reload’s its registers from
the EEPROM by means of the reload pin (RLOAD) or power
down the meter and power up again.
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
Total sum all three phases
Only phase 1 measurement
Only phase 2 measurement
Only phase 3 measurement
Absolute sum of all three phases
Only phase 1 measurement
Only phase 2 measurement
Only phase 3 measurement
The meter is now set up with the correct register values but not
yet calibrated.
The following example shows how to calibrate the meter
Use the rated conditions divider value and the channel
balance values calculated above and program the EEPROM.
Set the programmable adder for a single phase to be
measured. Measure the %error for each individual phase
without changing any of the calibration constants.
Example of calculating rated conditions and channel
balance values
Meter rating = 80A / 230V (The SA2005P only uses integer
values)
%Error=(Measured Energy-Real Energy)/Real Energyx100
Calculate the rated conditions:
The %Error will be worked back into the calculations above.
For the example we will assume a 1.5%, 5.2%, and 3.2% for
the three individual phases. The rated conditions value is
recalculated relative to the phase with the lowest error. Phase
1 has the lowest error so 1.5% = MinError;
Krx=642 000/Rated volt/Rated current/6400x3600x1000/512
Krx = 642 000/230/80/6400x3600x1000/512
Krx = 38.3327
Krx = 38 (round Krx) - convert to integer
Kr = 38 - 1 = 37
The value 37 is stored in the rated register (Kr).
10/16
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