Data Sheet AS8118

Revision 1.8, 15-Feb-05

Page 14 of 30

Parameter

Description

Number

of bits

Register bits

Settings

Default

F_led_sel

Select LED pulse

rate [imp/kWh]

3

[26:24]

[59:57]

000 : 100

001 : 200

010 : 400

011 : 800

100 : 1600

101 : 3200

110 : 6400

101

Pulse_lev

Central pulse_level

value

22

[23:2]

[56:35]

0x6A6D4

Bank01

Select PROM bank

0 or 1

1[1]

0 : Bank 0

1 : Bank 1

0

Sel_def

Select default or

programmed values

1[0]

0 : default

1 : programmed

Value

0

Not used

2

[69:68]

00

Total

70

The “Default” values are hard coded on-chip outside the PROM block. Only once the Sel_def bit has been set, are the PROM

parameters selected by the AS8118.

Two PROM banks are defined as ‘Bank 0’ and ‘Bank 1’. This feature allows for a complete reprogramming cycle if necessary.

The required bank is selected with the bit called Bank01.

The calibration of the AS8118 adjusts the specific pulse-level (Pulse_lev), which defines exactly the energy level when a

pulse has to be generated and presented to the output. This pulse-level is used to define a very fast internal pulse rate from

which the external pulse outputs are derived. Therefore, the AS8118 is extremely flexible in defining pulse output rates as

required for a specified kWh meter.

The parameters F_mon_sel, F_cal_sel and F_led_sel are used to define the pulse rates for the pins MOP/MON, CAL and

LED.

The Acreep_sel bit defines the threshold for the current for when no pulses should be transmitted.

Calculations for Calibration

This paragraph describes how to successfully calibrate the AS8118 device. The parameter Pulse_lev is the main parameter

to determine the basic internal (very fast) frequency. This frequency relates to the measured power and is the basis from

which all the output pulse rates namely, MOP/MON, CAL and LED are derived.

Prior to system calibration, the appropriate value for the parameter Pulse_lev must be calculated to produce the required

output pulse rates for MOP/MON, CAL and LED. The calibration exercise must accommodate all system non-idealities that

are present in the meter system.

There are two calibration methods available to find the appropriate value of Pulse_lev, namely:

-

Defined current and calibration time method

-

Comparison method

It is also possible to perform:

-

Calibration without on-chip programming