SA9109B
Display resolution
From the above formula for fP it can be derived that the slope constant, Ks, is given
by the following expression:
626 3600 1000 E
*
*
*
kWL
KS =
VL * IL
Where
EkWh
VL
= energy for 1 display increment in kWh
= rated line voltage
IL
= rated line current
This formula is valid only if 16µARMS flows into the current sense input for rated line
current (IL) and 14µARMS flows into the voltage sense input for rated line voltage (VL).
Offset Adjustment
The precision of this device does not require any offset adjustment for Class 1
metering. This facility has been provided to compensate for poor PCB layout or
circumstances requiring precision well beyond a Class 1 rating.
The offset of the device may be adjusted by programming a different offset into the
device during calibration. To calculate the offset the following procedure should be
followed:
Measure the linearity error at the current where offset correction is needed.
IM ERR
KO
=
*
IR
6
10-6
*
*
Where
IM = Measured current on the current sensor
IR = Rated current on the current sensor
ERR = Error ratio between the device and the Wh standard
KO = Offset constant (-127 ...127)
(The default value is 0)
Note that KO must be programmed as a integer value.
Meter/Manufacturers Identification Data
A total of eleven 4 bit words are available to store relevant data such as the meter
and manufacturer identification codes. For the optical interface protocol, the 4-bit
words are converted to 8-bit words (ASCII-format).
Writing to RAM
The memory is configured as ten 32 bit words. The programming data must be
written to the device as a bitstream containing a total of 320 bits. ROM-locations
will not be overwritten.
10/18
sames
SAMES [ SAMES ]
