For acquisition of the horizontal airflow and direction in tunnels,
tubes or similar applications.
Thanks to the high measuring rate, the instrument is also well-
suited for inertia-free measurement of gusts and peak values.
· The measuring values are available as analogue signals and/or data telegram via a serial interface
· Analogue output: Flow velocity with or without direction identification.
· Digital output: Flow velocity with direction identification and virtual temperature.
· The sensor arms are automatically heated in case of critical ambient temperatures, so that the function is guaranteed even with winterly
conditions.

1. Construction and mode of Operation
The Ultrasonic Anemometer 1 D consists of 2 ultrasonic transformers, facing each other at a distance of 200 mm. The transformers operate both as sonic transmitter and as sonic receiver. On starting a measurement a sequence of 2 individual measurements runs in 2 directions of the measurement section with highest possible velocity. The measuring directions (directions of sound propagation) are alternate. Two individual measurements are averaged and used for further calculation. The time required for a measurement sequence is approx. 10 msec at + 20°C.

2. Measuring principle
The velocity of the sound propagation in calm air is superposed by an airflow. From the difference of the propagation time of the sound with and against the airflow the velocity of the airflow is calculated. As the velocity of the sound greatly depends on the temperature of the air the propagation time of the sound is measured in both directions. This rules out the influence of the temperature on the measurement result.