WIKA A2G-85 User Manual

Page 11

WIKA operating instructions air2guide model A2G-85

40339564.02 07/2012 GB/D/F/E/I

6. Commissioning, operation

direct connection to a DDC or a monitoring system analogue 0 … 10 V

outputs are available.

ABCLogic™ - self-calibration feature

The outside levels of CO

are generally very low at 400 to 500 ppm.

Inside buildings people are the major source of CO

. When a building

is unoccupied for 4 to 8 hours, CO

levels will tend to drop to outside

background levels. This is especially the case when the building opera-

tional schedule includes a pre-occupancy purge of fresh air into the

building prior to the start of the day.

ABCLogic™, which stands for "Automatic Background Calibration",

uses the computing power in the sensor's on-board microprocessor

to remember the lowest CO

concentration that takes place every

24 hours. The sensor assumes that this low point is the value of the

outside level. The sensor is also smart enough to discount periodically

elevated display values, which might occur if, for example, a room was

used 24 hours a day. When the sensor has collected 14 days worth

of low concentration values, it performs a statistical analysis to see if

there have been any small changes in the sensor display regarding

background levels that could be attributable to sensor drifts. If the analy-

sis concludes that there is drift, a small correction factor is made to the

sensor calibration to adjust this deviation.

Commissioning of the sensors with ABCLogic™

When CO

sensors with ABCLogic™ are installed, they will use the first

14 days of operation to calibrate themselves to the local background

levels. Each sensor will calibrate itself to its environment over the first

14 days of operation.