Data Sheet AS8118

Revision 1.8, 15-Feb-05

Page 16 of 30

A logical flow of the described calculations, is shown below:

System Properties

Vmains

Imax

Calibration Setup

Ical

tc

System Nonidealities

ideal Pulse_lev

Number of pulses to

expect (ideal), Ni

Pulse Counting

real number of

pulses, Nr

Correction

Ni

Nr

ideal

Pulselev

lev

Pulse

*

)

(

_

=

Example

pulse rates are: Fmon: 200 imp/kWh, Fcal: 64

217962

435924

40

20

230

230

=

=

*

A

A

*

V

V

)

ideal

(

lev

_

Pulse

The ideal number of pulses during 20 seconds of calibration is:

imp

imp

.

*

A

*

V

*

s

*

*

kWh

/

imp

Ni

164

56

163

1000

3600

10

230

20

64

200

≈

=

=

Thus 164 pulses are expected during the 20 seconds calibration time. (For this example it is not important what error is

introduced with this setting!).

Assuming that 170 pulses were actually counted. The real pulse level may then be calculated:

225936

2

225936

164

170

217962

≈

=

=

.

*

)

real

(

lev

_

Pulse

This pulse level must then be written to the PROM so that Nr equals Ni.

Comparison Method

Most common, is the comparison of energy reading of the meter under test against a standard or reference meter. Normally,

the standard, or reference meter has a considerably higher pulse rate than the meter under calibration. In this case, the

absolute calibration time is not important for the calculations. The basic calibration setup is shown below: