Air flow measurement based on difference of transition times of ultrasonic pulses
The t/FL-USX ultrasonic air flow measurement system measures the air flow using the ultrasonic transit time difference method. The air flow is measured across the entire tunnel cross-section. The method therefore offers a much more reliable determination of the average flow velocity than single or two-point measurements.
Two sensors are mounted below the tunnel ceiling, cross section with an angle of 30° to 60° (usually 45°) such that a vector component of the air flow overlaps the direction of the ultrasonic sound pulses exchanged by the two sensors.
Air flow in the tunnel influences the transition time of the pulses between sender and receiver. Based on the difference in transition times of ultra-sonic pulses sent in one or the other direction the measured values are calculated. Measured values are air speed, air flow rate, direction of air flow and air temperature.
t/FL-USX Air flow monitoring system – Ultrasonic cross-section
- Accurate ultrasonic air flow measuring system based on different transition times of ultrasonic pulses
- Measurement of average air flow over the whole tunnel cross section
- Sensor setup via service interface
- • Suitable for tunnel cross sections up to 18 m (Measuring path up to 25 m)
- Connection to tunnel control system either via analogue output and relaysor via RS-485 MODBUS RTU
- Visible LEDs to indicate sensor status
- Corrosion-resistant non-wearing polyamide membranes
- Optional, remote touch operating unit to display measured values and to modify parameters
System setup
Air flow sensor A (Master)
The master sensor is mounted on one tunnel wall and aligned with the slave on the opposite wall.
Air flow sensor B (Slave)
The slave sensor is mounted on the other tunnel wall and aligned with the master.
Terminal box Master
The terminal box on the master side is used to connect the power supply and the connections to the slave as well as the tunnel control system.
Terminal box Slave
The connection box on the slave interconnects to the master’s terminal box.
Connection to the tunnel control system
The tunnel control can be connected by analogue outputs and relay contacts or RS-485 MODBUS RTU.
Touch operating unit (optional)
The touch operating unit displays measured values and status. It can also be used to configure the system. One operating unit can connect up to 3 air flow monitoring systems.
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