SA9603C

sames

10/18

6.

Register Values

a.

The active and reactive energy measured per count, may be calculated by

applying the following formula:

Energy per Count

=

V * I

Watt seconds

K

Where

V

=

Rated Voltage

I

=

Rated Current

K

=

9281

for Active Energy

9281 * 2 for Reactive Energy

π

b.

The mains frequency may be calculated as follows:

Frequency

=

Crystal frequency

Register Value * 8

c.

To calculate the measured voltage, the following formula may be used:

Vmeasured =

V * n

14000 * t

Where

V

=

rated mains voltage

t

=

time difference between successive reads

n

=

difference in register values between

successive reads

7.

Software Flow

The SA9603C is able to execute code written for the SA9103C without any

modifications. (Ensure that only bits of the serial command to the device is set that

need to be set.)

It is suggested that the DUMP command is used in cases where more than one

register is continuously read. The DUMP command initiates a serial transmission

of successive register values, starting with the specified register. The Dump

command does not reset the register values.

New software should be developed in such a way that registers are never resettled

and must allow for register overflow. Register overflow is easily taken into account

by software running on a controlling microcontroller. The software subtracts the

previous register value from the current register value in order to determine the

actual change in register value. Note that the mains frequency register value only

needs to be scaled, in order to calculate the true mains frequency in Hertz.

The SA9603C integrated circuit only transmits the register values after completion

of the current measurement cycle (8 mains periods maximum).

The delay of 8 mains periods may be calculated from the period value of the

frequency returned by the initial read, and updated with each subsequent frequency

reading.