Converting readings into measured values

AN3254

16/24

Doc ID 17783 Rev 1

5

Converting readings into measured values

5.1

Energies

The first three registers contain 20-bit values of the internal 3-phase energy up/down

counters, and in the following groups there are the registers containing each phase energy

counter.

The value of the least significant bit of every energy counter is related to power meter

constant P, which is the number of pulses per kWh that the meter, through calibration, is

configured to provide to the LED pin.

This means that this value changes with the application and relative calibration.

Given P, the number of pulses per kWh provided, the energy registers LSB value is indicated

in Table 2 below:

For example, the energy registers LSB values for SYS = 0, 1, 2, 4, 5, 6, 7 when P = 64000

pulses/kWh = 17.7 Hz*kW are:

The energy registers LSB values for SYS = 3 and the same P are:

Table 2.

Energy registers LSB value

Register

SYS = 0,1,2,4,5,6,7

SYS = 3

3-ph Active Energy Wide Band (P)

3-ph Reactive Energy Wide Band (Q)

3-ph Active Energy Fundamental (F)

3-ph Reactive Energy Fundamental (R)

K

P

1000

P2

10

⋅

----------------- Wh

[]

=

K

P

1000

P2

10

⋅

----------------- Wh

[]

=

K

Q

1000

P2

10

⋅

----------------- VArh

[]

=

K

Q

1000

P2

9

⋅

-------------- VArh

[]

=

K

F

1000

P2

10

⋅

----------------- Wh

[]

=

K

F

1000

P2

9

⋅

-------------- Wh

[]

=

K

R

1000

P2

10

⋅

----------------- VArh

[]

=

K

R

1000

P2

9

⋅

-------------- VArh

[]

=