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Theoretical Background
I found this great article in Elektor 06-2012, written by Marc Gerin (France), which explains the working principle and electro-mechanical design of such a device.
FIRST PROTOTYPE
The prototype had a simple pen case connected to 1 inch water differential pressure sensor. It is very simple, and anyone can do it at home. The sensor I used is 1 INCH-D-4V R8C13-1 and it is little expensive ~$100.
The total pressure port is an empty plastic ink tube that runs from the nozzle to the back of the pen.
Static pressure holes are drilled in the outer shell of the pen
The total and static pressure ports are located at the back of the pen
The prototype device performs very well, but it is too big and unsuitable for mass production.
The differential pressure sensor is connected to the output ports on the back of the Pitot tube. The sensor is a 1-inch-water-column differential pressure sensor by All-Sensors. It provides a 4-volt output signal at maximum differential pressure (1 INCH-D-4V R8C13-1).
RC-Model version
The main difference for the model is that the static pressure can be measured inside the model body, so a simple and small intake port will serve as the Pitot Tube and the total pressure can be "delivered" to the electrical sensor by using a simple silicon tube. I used it in two of my models and got excellent results (Maybe I will publish them later on)
FIRST PRODUCTION VERSION
dimension: 90x50x15mm
Weight: 15 gr. 5.2gr without the sensor and electronics
The CAD version
The 3D-Printed version
Without getting into the precise manufacturing details and electrical design, the final 3D-Print KIT looks like this:
Left - Outer locking ring 1.5g
Middle Pitot-Tube with sensor and electronics (the PCB is not present in the picture) - 7g
Right - Body shell 6g
The full Pitot-Tube with electronics & body shell weighs less than 15g
If mounted in an RC model, the sensor and electronics can be inside the model's body. The body shell and outer lock parts are not needed, and the total weight is reduces to less than 7.5g.
After gain & offset calibration the results are very accurate and linear. The dynamic range is suitable to RC models.
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