AS8268 datasheet(30/136 Pages) AMSCO

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Data Sheet AS8267 / AS8268

Revision 1.0, 19-Jun-07

Page 30 of 136

Reference

Meter

MUT

Pulse Counter

led

IO1

Figure 4:

Basic setup for comparison calibration method (using IO1 as example input)

Note: An I/O used as push-button input can be used for the input of the reference meter pulses during

calibration.

The standard or reference meter pulses are counted between two pulses from the meter to be calibrated.

Ideally the sum of the pulses would exactly be the ratio between standard meter or reference pulse rate and

the pulse rate of the meter under test. From the deviation the corrected Pulse_lev may be calculated.

)

ideal

(

lev

Pulse

)

corrected

(

lev

Pulse

The ideal number of pulses Ni is the ratio between the pulse rates of the reference meter and the meter under

test, which is always >1. The formula for Ni is as follows:

)

mconst

(

Rate

Pulse

LED

)

ref

(

where PR(ref) is the reference meter constant.

The Pulse_lev (ideal) is calculated using the following formula:

)

default

(

lev

Pulse

230

)

ideal

(

lev

Pulse

max

mains

Example

The reference meter has a pulse rate, which is 10,000 times greater than the pulse rate of the AS8267 /

AS8268 LED output.

LED Pulse Rate

= 3,200i/kWh

PR(ref)

= 3,200 x 10,000

⇒ Ni = 10,000

During a calibration cycle we measure 11,000 pulses between two LED pulses.

⇒ Na = 11,000

Assuming a meter with Vmains = 230V

Imax = 60A

where Ni is the ideal number of pulses

and Na is the actual number of pulses

(PCNT register in MPIO).

The actual number of pulses is available

in the pulse count register (PCNT).

AS8268 Datasheet(PDF) 30 Page - ams AG

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