SA9109B
The kWh values of the LCD display digits, are given in the table below. The
resolution of the Least Significant Digit is normally programmed to 0.1kWh:
10
5
4.
10
4
10
3
10
2
10
1
10
0
10
-1
kWh
Device Programming
The SA9109B 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
I
I
.I
V
40062.5
f
P
= 11.16 *
*
*
3.5795MHz
I
R2
K
S
Where
FOSC
I
I
I
V
I
R
K
S
= 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)
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*
P ulses / s
D isplay
Incr em ent
f
p
1/K
s
1 / 64
D R -0 1 2 5 6
* At rated conditions
The display is incremented after every 64th pulse on SDO.
sames
9/18
SAMES [ SAMES ]
