SA9110A
4.
Device Programming
The SA9110A contains on-chip registers which enables the meter manufacturer to
store various data:
Slope Adjustment
The slope of the device may be adjusted by programming a slope constant (K
S
) into
the device during calibration. The output frequency at SDO (f
P
) is calculated by
means of the following formula:
FOSC
40062.5
(I
I1
* I
V1
) + (I
I2
* I
V2
) + (I
I3
* I
V3
)
f
P
= 11.16 *
*
*
3.5795MHz
K
S
3 * I
R2
Where
FOSC
=
Oscillator frequency (2MHz ...... 4MHz)
Input current for current sensor input (16µA at rated line current)
Input current for voltage sensor input (14µA at rated line voltage)
Reference current (typically 50µA)
Slope constant (1025 ... 16384)
(The default value is 11389)
I
I1,
I
I2
, I
I3
=
I
V1
, I
V2
, I
V3
=
I
R
K
S
=
=
By changing the slope of the device the resolution of the LCD together with the pulse
rate on SDO may be changed by up to an order. The block diagram below illustrates
the display update rate.
Programmable slope divider
40062.5*
Pulses / s
1/K
s
1 / 64
Display
Increment
f
p
DR-00956
* At rated conditions
The display is incremented after every 64th pulse on SDO.
Display Resolution
From the above formula for f
p
it can be derived that the slope constant, K
s
, is given
by the following expression:-
K
s
= (626 * 3600 * 1000 * E
KWh
) / ( 3 * V
L
* I
L
)
Where E
kWh
=
energy for 1 Display increment in kWh
V
L
=
rated line voltage
I
L
=
rated line current
This formula is valid only if 16µA flows into each of the current sense inputs for rated
line current (I
L
) and 14µA flows into the voltage sense inputs for rated line voltage
(V
L
).
9/18
sames
SAMES [ SAMES ]
