Dwyer 670 - Manual (Page 10)

9
1.2 Alarm Configuration/Calibration
The alarm is supplied with a factory configuration.
The only part of the configuration that can be changed is the setting for the Sash High timer delay and
the percentage figure for the Low Air alarm point when using the two point calibration mode.
The alarm has two modes for the calibration of the airflow alarm point. These two modes are
selectable via a ‘jumper connection’ on the back of the alarm PCB. The jumper is labeled as CAL and
is situated on the edge of the PCB above the Com port.
The two calibration modes are:
a. Single Point Calibration (with the Jumper connected) - The airflow is reduced
mechanically (using balance damper or slowing down the extract fan) to the Low Air alarm
point and this air flow is ‘captured’ by the alarm. The airflow is then restored to the normal
operating value and the Low Air alarm will activate if the airflow subsequently falls to the
alarm point.
b. Two Point Calibration (with the Jumper not connected) - This is a two point calibration
method. The airflow is set to the normal operating value and this value is ‘captured’ by the
alarm and taken to be 100%. The airflow is then increased to one and a half times the
normal operating value and this value is ‘captured’ by the alarm and taken to be 150%.
The Low Air alarm will then activate if the airflow subsequently falls to 80% of the normal
operating value.
Note: For fume hoods where it is not possible to use the side wall sensor connection the sensor can
be connected directly to the extract duct using adaptors and a 1/4˝ PVC tube - see installation section
for details. Only the Single Point Calibration method can be used for this configuration.
See ‘Quick Start Installation’ below for details of the Calibration procedures.
AV-670:B-32 10/1/09 2:20 PM Page 10