Chapter 6: Maintaining Your Filtered Enclosure
OPTION
Calibrate and Operate the Airflow Monitors
Guardian Airflow Monitor (LED Monitor)
Refer to Figure
Labconco Airflow Monitor / Airflow Switch Operation
The Guardian Airflow Monitor (LED) consists of a circuit board and an airflow switch. This switch indicates airflow as safe or low. It does not provide an actual face velocity, but a small setscrew in the back of the sensor can adjust the airflow level that it classifies as “good/safe” or “low/alert.”
The circuit board provides power to the sensor and also contains a “safe (green)” and “alert (red)” airflow LED indicators, as well as a “SILENCE ALARM” button to quiet the audio alarm. When first powered up, the PCB will light both red and green LED indicators and sound the alarm to indicate it is working. After 5 seconds, the air monitor will indicate either good or bad airflow based on what the connected airflow switch detects. For low airflow, the unit will wait for 10 seconds of bad indications before it sounds both the audio alarm and the red “alert” LED indicator. If the “SILENCE ALARM” button is pressed, the audio alarm will be silenced, but the red “alert” LED will remain on. The alarm is silenced indefinitely unless an airflow change is detected. If safe airflow is later detected for 10 seconds, the green “safe” LED will be lit and the “alert” (red) LED will be shut off. At any time the airflow is safe/good, one can press the SILENCE ALARM test button and the audio alarm and the red LED will turn on as long as this button is held down. The PCB has also a
The PCB is mounted behind the front panel using standoffs and an appropriate label is used to highlight the “SILENCE ALARM” button with clear areas for the red and green LED’s. No holes to allow sound to be broadcast louder are necessary.
The PCB can be prepared as a factory special with an additional connector for the following external inputs, and having the following possible functions:
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