Series 1780 - Pressure Sensor for Airspeed Measurement
Save time and improve repeatability of your tests in wind tunnels. The pressure sensor is compatible with the RCbenchmark Series 1780 Dynamometer 25 kgf, 40 kgf and 75 kgf. It is a precision differential pressure sensor fully integrated with the RCbenchmark software. Measurement range is ±6.8 kPa, which allows measuring all range of airspeeds typically encountered by UAVs.
This pressure sensor is meant to connect to the pitot tube that is part of your existing wind tunnel installation.
A pitot tube is not included with the sensor.
Only one pressure sensor can connect to the Series 1780.
This product includes:
- The differential pressure sensor (1)
- 1.2 m long of 2 mm inside diameter tubing to connect to your pitot tube (2)
The sensor measures the pressure difference “△P” between the static pressure inlet and the dynamic pressure inlet of the pitot tube. Use this formula to calculate the wind speed:
where rho is the air density. The air density is calculated with the ambient pressure and temperature, assuming dry air. The pressure sensor also measures the temperature, but the user must supply the ambient pressure in the "Utilities" tab of our software. By default, the ambient pressure is 101.325 kPa.
Measurement noise level and pressure measurement
The airspeed is proportional to the square root of the pressure. The sensor has a peak to peak noise of around 1 Pa. At 0 m/s, the noise will be ± 1 m/s. At 20 m/s, it will be ± 0.02 m/s.
1) Connect the pressure sensor to one of the “Addons port” of the Series 1780 Main board.
2) Connect both included tubes to the probes’ measurement inlets.
3) Connect one tube to your pitot tube’s static pressure inlet and connect the other to the dynamic pressure inlet. The order of connection is not relevant.
4) Restart the app.
5) The airspeed is displayed in the software interface and the log file when the sensor is connected.
When the air is at rest before a test, you should press the “Tare Airspeed” button that appears under the “Tare load cells” button on the left of the interface.
Our tests show that the sensor has an accuracy of 1% FS when tared but not calibrated. Although not necessary for most applications, you can also calibrate your sensor.
If you are calibrating your sensor, first select the displayed unit of pressure as mm of H2O (or as inch of H2O) in the “Setup tab”. Then go to the “Utilities” tab and connect the sensor as shown below. The blue parts of the drawing are water. You can use a large cup to contain the water. The distance “d” should be precisely measured. We recommend using a “d” of around 50 cm, but not more than 70 cm.
To calibrate the sensor:
1) Place the water container with the tube on the lower surface as shown in Fig. 1.
2) Press the “Tare airspeed” button.
3) Place the water container on the higher surface. The distance d should be about 50 cm (20 inches) to minimize errors.
4) Adjust the calibration coefficient until the pressure value matches the height difference “d”.