Ametek Thermox WDG-V, User Manual

Page: 30 / 164

2-8 | Thermox WDG-V / VC / VCM with Blow Back
Flow Sensor
OverviewThe aspirator creates a vacuum and pulls the process gas into
the analyzer. There are two paths for the gas to take:
1. Immediately back to the process gas.
2. Through the sample loop, past the cell and/or combustible detector.
• Calibrated at the factory, the flow sensor measures the sample flow
through the sample loop. The flow measurement is updated every 90
seconds. This delay is used to allow the sensor to effectively auto-zero
to prevent false alarms.
Alarm Limits
The flow sensor reports flow as relative to ideal (ie. 100% is ideal flow,
50% is half of flow). An alarm is generated when the sample flow is less
than 45% ideal.
The flow measurement is directional, with reverse flow generating an
alarm.