Application

Sequence of Operation

AVS Calibration

Siemens Industry, Inc.

Application Note, App 2926

140-1308

2015-07-07

AVS Calibration

Calibration of the air velocity transducer(s) is periodically required to maintain accurate

air velocity readings. Depending on the value of CAL SETUP, calibration takes place

either at fixed time intervals or whenever the application goes into unoccupied mode.

When calibration is in progress, CAL AIR equals YES. After calibration, CAL AIR

returns to NO.

The application uses Autozero Modules connected to AUTOZERO DO8. This means

that the supply and general exhaust flow control devices do not close during calibration

of the transducers.

NOTE:

The LCM does not monitor Fume Hood flow changes for 3 seconds during AVS

calibration.

Venturi Air Valve Calibration (Mode 1, 3)

Calibration of the Venturi Air Valve(s) must be performed at least once during start-up

to determine the relationship between airflow and the voltage curve of the actuator.

WARNING

The LCM cannot calibrate the supply and general exhaust Venturi Valves at the same

time.

They must be calibrated separately.

Prerequisites for calibrating Venturi Air Valves:

 Fully operational supply and general exhaust airflow systems.

 Supply and general exhaust Air Velocity Sensors are calibrated and working

normally (SUP AIR VOL and GEX AIR VOL cannot be Failed).

The supply or general exhaust Venturi Air Valve is calibrated by setting CAL SUP VLV

or CAL GEX VLV to YES. Calibration proceeds automatically and takes about 3

minutes, after which CAL SUP VLV (or CAL GEX VLV) returns to NO. If calibration is

successful, SUP VLV STAT, or GEX VLV STAT, is set to PASS. A failed calibration

requires checking the equipment for possible causes—loose or kinked flow sensor

tubes, improper actuator or valve operation, etc.—followed by recalibration.

NOTE:

The factory default value of SUP VLV STAT and GEX VLV STAT is NOTCAL. The

value of SUP VLV STAT or GEX VLV STAT is set whenever a calibration or table

transfer is performed as the last step of the calibration/table transfer. SUP VLV STAT

and GEX VLV STAT are never used for active control decisions.

When calibration is complete, the EEPROM automatically stores a table statement of

voltages (no loss of values upon power failure) that will be output to the AO point, SUP

DMPR AO2 or GEX DMPR AO3, to drive the actuator.