71M6515H_11 Datasheet, PDF (27/60 Pages) Teridian Semiconductor Corporation – Up to 10ppmC precision ultra-stable voltage reference Digital temperature compensation

71M6515H
A Maxim Integrated Products Brand
Energy Meter IC
DATA SHEET
JULY 2011
We calculate PHADJ from φS, the desired phase lag:
[ _[ ] _{] PHADJ}
=
2
20



(1
−
tan(φ_S ) 1 + (1 −
2^−9 ) sin(2πf₀T )
2^−9 ) ² −
− tan(φ
2(1
S ⁾¹
−
−
2^−9 ) cos(2πf₀T )
(1 − 2^−9 ) cos(2πf
0^T
)



Finally, we calculate the new calibration current gain coefficient, including compensation for a slight gain increase in the phase
calibration circuit.
CAL _ I _NEW
=
CAL _ I
A_XI
1
1 + ^{2−20 PHADJ (2 + 2−20 PHADJ − 2(1 − 2−9 ) cos(2πf0T ))}
1 − 2(1 − 2^−9 ) cos(2πf₀T ) + (1 − 2^−9 )²
Calibration with Five Measurements
The five measurement method provides more orthogonality between the gain and phase error derivations. This method
involves measuring EV, E0, E180, E60, and E300. Again, set all calibration factors to nominal, i.e. CAL_IA = 16384, CAL_VA =
16384, PHADJ_A = 0..
First, calculate AXV from EV:
1. A_XV = E_V + 1
Calculate AXI from E0 and E180:
2.
E₀
=
IV
A_XV A_XI cos(0 − φ_S )
IV cos(0)
−1 =
A_XV
A_XI
cos(φ_S ) −1
3.
E₁₈₀
=
IV
A_XV A_XI cos(180 − φ_S )
IV cos(180)
−1 =
A_XV
A_XI
cos(φ_S ) −1
4. E₀ + E₁₈₀ = 2 A_XV A_XI cos(φ_S ) − 2
5.
A_XV A_XI
=
E₀ + E₁₈₀ + 2
2 cos(φ_S )
6.
A_XI
=
(E₀ + E₁₈₀ ) 2 + 1
A_XV cos(φ_S )
Use above results along with E60 and E300 to calculate φS.
7.
E₆₀
=
IV
A_XV A_XI cos(60 − φ_S )
IV cos(60)
−1
= A_XV A_XI cos(φ_S ) + A_XV A_XI tan(60) sin(φ_S ) − 1
8.
E₃₀₀
=
IV
A_XV A_XI cos(−60 − φ_S )
IV cos(−60)
−1
= A_XV A_XI cos(φ_S ) − A_XV A_XI tan(60) sin(φ_S ) − 1
Page: 27 of 60
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