SDP33 with pitot of different tube diameter

Hi, is it possible to use the right pitot tube with an SDP33 sensor? The left one is the original one, but I can’t get it, I only have the one on the right that has a different tube diameter. I understand that for static measurement it is not a problem, but for dynamic measurement it might not work properly?
Thank you!

The size of the output tubes do not matter here. Just be sure whatever tubing you have that connects between the pressure sensor and probe is secure.

Your new pitot-static probe looks like a much nicer probe with a proper tip to it too. (Though a bit bigger.) :slight_smile:

Would please link to where you found that?

By the way neither of the pressures on the output of a pitot-static probe is dynamic pressure. The front port pressure is the stagnation pressure and all of the holes around the side are the static pressure ports.

The dynamic pressure is measured by placing those two pressures on opposite sides of a differential pressure sensor. The membrane in the middle of the sensor moves back and forth depending upon the differential in pressure.

Here is a graphic I found that shows this.


Thanks Josh for your detailed answer! I am attaching the link below, but if it doesn’t work correctly (it’s a bit long link), you can search for pitot on Aliexpress and it will appear first in the listings.
Good flights!

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Thanks! Bookmarked it for later.

Josh, I’m afraid you are wrong.
Technically you are right, if the sensor is a real differential pressure sensor.
But the problem is that SPD33 is not a differential pressure sensor, but rather an air flow sensor. (It measures the cooling of a resistor). As far as I know ,the current implementation in the code is for 1.5mm diameter pitots. Larger diameter will give you false measurement. Plus tube length will count as well.

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Ekk! Well that serves me right for jumping right to Sensiron’s page and seeing differential pressure sensor every where when it really truly is a mass flow sensor.

Thank you for the correction!

It looks like though @vascodx 's new Pitot-static is a much closer match to the one from DroTek. Though he will want to check if it has similar measurements to the assumed model and beware of possible issues.

From pulling out the calibration model used from here

The relevant parameters are:
Pitot-tube tip diameter: 1.5mm
Tubing Length: 4.5cm with inner diameter of 1.8mm?

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