Introduction
![](images/windvane.jpg)
Wind sensors have traditionally been mechanical devices. The disadvantage of mechanical sensors, like the anemometer and the wind vane is that they need regular maintenance. There are also non-mechanical wind sensors, like the Ultrasonic and the Laser-Doppler sensor but those are very expensive.
![](images/sensor1.jpg)
At the Electronic Instrumentation lab we have been working on a cost-effective, low-power, accurate, solid state wind speed and direction sensor. The sensor has no moving parts therefore it is robust and essentially maintenance-free. The first ideas and designs originate from as early as 1983.
Early Operating principle
![](images/finger.jpg)
The idea of measuring wind direction and speed started based on the principle of thermal measurement, much like we do as a human, sticking your finger in the air, ‘feeling’ where the wind is coming from.
![](images/principle.jpg)
This idea has translated to thermal measurement on a chip:
The center of a plate is heated above ambient temperature. When an airflow passes the plate the temperature pattern will be shifted depending on the direction and speed of the airflow, so inducing a temperature gradient dT, measured at points A and B we obtain both wind speed and direction.
Smart wind sensor
![](images/chip.jpg)
Since the 80’s the sensor has evolved into a smart, accurate, low-power, solid state wind speed and direction sensor.
The main differences:
- Measure heater power and adjust it so that temperature differences are canceled (thermal balancing) i.o. measure temperature differences only.
- All electronics on-chip, SD (Sigma-Delta) conversion i.o. analog electronics, outputs can be directly connected to a microprocessor.
- No trimming required.
- Reduced power consumption, 25 mW i.o. 1500 mW.
Specifications
Operating range | 0…25.5 m/s |
Minimum wind speed | 0.2 m/s |
Inaccuracy (typ.) | Speed: ±0.5 m/s or 3% Direction: ± 3° |
Resolution | 0.1 m/s |
Response time | < 1 s |
Measurement rate | 3 Hz (speed & direction) |
Dimensions | ∅ 120mm, height 105 mm |
Power consumption (max) | 25 mW |