Monitors maintain accurate response even when using low-flow hood conditions. Alarms activate based on sustained low-flow condition. Use pushbuttons to set alarm and perform easy two-point calibration. Monitors will also indicate high sash condition (requires proximity switch, not included) with Configurable time delay. Record hood performance using RS-232 connection to computer. AFA500 33556-50 features a horn alarm with green and red LED indicators. The graphic display AFA500 33556-60 comes with an external velocity meter and shows current velocity in FPM with bar graph depiction of recent hood airflow performance; calibration instructions appear on screen. Choose AFA500 33556-70 for its extra wide measurement range. It includes a remote velocity probe which can be installed in your ductwork for use with Biosafety cabinets. Reliable, durable sensor element simple field calibration. Multiple alarms-audible, visual, and relay.