SpeedPilot - Page 3 - RC Groups
Thread Tools
Apr 06, 2012, 05:57 PM
I bail out, anywhere, anytime
Taurus Flyer's Avatar
Originally Posted by Anker
Thanks Dan,

I am waiting for weather that's warm enough to allow me to calibrate the pitot tube and pressure sensor by holding the pitot tube at arms length out my car window or on some kind of support.

How is calibrating going, any results to show?
Justy finished the electronics for a hot wire airspeed measuring system, so time to calibrate.

Sign up now
to remove ads between posts
Apr 08, 2012, 02:21 AM
Registered User
Hi Taurus, old school but good job , I like this kind of experimental setup. What thermistor are you using ? self made ? How do you calibrate ? How did you shaped the ring tube ?
I used a U-manometer to test mine but I don't have a solution in mind for yours, I'd like to know.
Apr 10, 2012, 08:20 AM
I bail out, anywhere, anytime
Taurus Flyer's Avatar

Do you know Jean de la Fontaine?

Apr 10, 2012, 01:13 PM
Registered User
Oh yes, he has a shop downtown where you can find RC stuffs, he has a glider to sell, the Fable, incredible machine !
Aug 30, 2013, 02:06 PM
I bail out, anywhere, anytime
Taurus Flyer's Avatar

When Moses isn't going to the mountain than I have to bring the mountain to Moses.

Originally Posted by HLGNut
Back in 2006, I put together a telemetry system for our XC team. Our biggest problem was getting a consistant data transmission; using at that time, some Aerocomm tranceivers on 900MHz. The project was shelved due to these transmission issues. The XBee modules from Digi are a better choice now.

I was working on the airspeed portion of the sensor system and found that the airspeed to voltage (from the pressure sensor) was not exactly linear so I developed a lookup table from the calibrated values. I've included that table, charted, as well as some other useful PDFs.

The airspeed sensor consisted of a 0 - 5 inch H2O pressure sensor driving the 10 bit A/D of a PIC processor. I was using a Pitot tube with a built in static port. This 5 inch pressure senssor had way too much range for actual use - I would go with a much smaller one now.

To calibrate the sensor and generate the table I bought a 0-120 MPH speed gauge from Airplane Spruce. I plumbed the gauge into a "Y" connector connecting the gauge, the pressure sensor, and 60cc syringe which provided the pressure. I had the PIC spitting out the A/D values to my PC. I then just applied the pressure until the gauge read say 20MPH and then recorded the A/D value. Continuing I ran it to 70MPH and that is the chart I've provided.

If I were to do it again, I would go with a different sensor, possibly the one I specified here.

I hope this helps.


- Bob -

When selecting a differential pressure transducer take account for the max airspeed that can be reached. The transducer has to be able withstand this without deformation. You have to count with (about) doubling the differential pressure for 40 % extra speed range.
Is max speed 90 mph, diff. pressure is 4.2 "wc, for 126 mph we have to count with a differential pressure of about 8.2 "wc.

Aug 30, 2013, 04:06 PM
Who needs a pilot??
danstrider's Avatar
Slightly off topic, has anyone seen this new meas-spec sensor yet (http://meas-spec.com/downloads/MS4515HRD.pdf)? It reads the same as the MS5611 that a lot of vario guys are using.

Reason I bring it up is that the sensor comes factory-calibrated. Would still have to convert dynamic pressure to airspeed...

Last edited by danstrider; Aug 30, 2013 at 04:31 PM. Reason: fixed link
Aug 30, 2013, 04:09 PM
I bail out, anywhere, anytime
Taurus Flyer's Avatar

link: page not found!

Last edited by Taurus Flyer; Aug 30, 2013 at 04:15 PM.
Aug 31, 2013, 01:17 AM
I bail out, anywhere, anytime
Taurus Flyer's Avatar
Scott, Dean

Originally Posted by marnochs
WS-tec is the only Vario that offers a voice layer airspeed anouncments.(I think they're the only one, all the rest are "data on a screen" type) I did put a bug in Rick's ear about it though.

Looks like I'm going to filally have to hook up my WS tec airspeed sensor and see what it's like.

The Airspeed anouncments are switch selectable via one channel / 3-position switch (on/off in one of the modes) and there are time or speed interval settings. If the anouncments are like the altitude it will be the number only not " your speed is xxx"

Then I could spend time finding what speed the best sink rate is ---all kinds of fun to be had.
And of course avoid the dreaded Vne


Originally Posted by DEAN GRADWELL
Hope you have better luck than me. I bought one because of the speed function, varied so much it was worthless.

RGGroups forums do have sophisticated search functions to by using "key words".
It's better to continue this subject in a thread with related subject name.All these data and experiences will be easy to find back that way when somebody needs these.
This can be that related thread, I searched and restarted this thread especially for you.

Regards wit CAS


Thread Tools