New Airspeed sensor (MS5525) for ArduPlane 3.8

@flyingw I’d look at the dataflash log and graph the airspeed temperature. I’ve noticed significant drift with MS5525’s that is associated with the sensor warming up.

Here is the temperature for the flight. It appears to be decreasing:

It is decreasing, but that’s not actually a very large temperature shift. I was expecting something more on the order of 10-20 degrees Celsius.

Exactly what I was going to say. single digit variation, not even 3 'C.
Most flight we can actually expect much more.
As I have said many times the unit is still not ready for prime time.

I think I will ask mRo to take a look at my unit - their customer support is very good.



From what I have seen so far, most users have a favourable review of the MS5525.

However, recently I have been testing the noise levels in my new MS5525 sensors. They keep giving greater noise than the old 4525DO sensors. I have opened a discussion thread regarding this issue here.

Anyone else experienced noise problems with their MS5525 sensors?

Any news on the problem of MS5525?

Hi mark, i noticed you said you used a pixracer and a airspeed sensor,
Was it i2c on the same port as the gps/mag?
Im having trouble getting my airspeed to function when its connected with the gps. Did you have any trouble like this?

Yes, I used the stock mRo cables and the “active” I2C hub:

Thanks for that,
Im using the later V1.1 airspeed with logic level shifter on the sensor board, so it should be the equivalent setup,
There’s no boosting/extra pull ups going on with mine, but the pixracer already has pull ups in its i2c port.

I’m not aware of a V1.1 MS55525… and I don’t see it mentioned in the mRo store.

Thanks Mark,

There are many issues here. It is a generic Pixracer that has a MPU6000 and MPU9250, no standalone MAG. That does not match any official Pixracer spec. The GPS is also generic. The only thing I can confidently support is the mRo airspeed sensor. Since the I2C HMC5983 MAG on the GPS and the Airspeed sensor both work when used standalone, my best guess is a wiring issue.

We do offer a 5525 which is supposed to be an upgrade to the 4525.

Oh, I assumed we were talking about a genuine Pixracer such as I used in my Convergence.

Sorry mark, it is a 4525 v1.1 not a 5525. I was just differentiating it from the 5v logic 4525v1.0.
And yes, everything other than the sirspeed sensor are clones as i am brand new to this and have already crashed the first platform on the first flight (pilot error) and have also crashed the second platform on the first flight (again, pilot error) and as such i was trying to atleast get things sorted so that i can have some success before i invest in the ‘real deal’.
I will happily vlog for others, that this is not a good idea as i now know, because although the case of this stuff (loosely meaning anything from china sold cheap on BG, ali, ebay, etc) looks similar to the real thing, internally they are too different and not a workable proposition.

And no, I had no problems at all with the mRo Pixracer, GPS and MS5525 airspeed sensor described in my blog post.

Regarding good investments: it is rare (in my experience) to damage the FC or GPS (or other sensors) in a crash, even with racing quads. Props, motors and ESCs are a different story :slight_smile:
So my opinion is that the extra money you spend on your control electronics should save you time and money spent repairing airframes and replacing props etc. Not to mention the time and frustration involved when dealing with suspect hardware.

Yes, i have been so far able to salvage equipment from each crashed platform to install in the next. However i wasn’t sure this would be the case initially when buying the equipment. Also there is the potential to loose it all with a crash into water etc,
But you are right about the time spent trying to get clone equip working,
It is however, a bit confusing for the naive, it’s not like there is ‘ardupilot’ branded hardware and everything else is a copy. Instead there is many brands and many more copies, maybe even copies of copies. I also have a holybro pixhawk 4 with the associated external gps/mag and power module, but i dont know if it is a proper Flight control either, I thought the pixracer clone, i purchased would have the same hardware as the ‘original’ (if there is one such original) but that the fc i purchased would not have the same QC as the real one.

For the new like me It’s different to the proprietary systems, in which its very obvious to see a dji phantom for sale at a local electronic store for example, and i know that its the genuine dji product.

With open source, if i decide i want to have an ardupilot based flight control system, there is not one such genuine ardupilot hardware, theres endless confusion for me about pixhawks and pixhawk4’s (not to be confused with PX4) which are really a pixhawk 1, the predecessor to a pixhawk 2, and there are mRo and holybro and 3dr who all seem to make their own version of each FC, whose product is the real one and whose are copies? My holybro pixhawk4 looks like a 3dr pixhawk4,
Sorry for the rant, i realise that the answers to all my questions are in the ardupilot docs and forums already, i just have to keep reading and learning as i go.

I agree that with the open source designs that you don’t know what you’re buying unless you go to a trusted distributor. The closed designs are not so easy to stamp out with counterfeit parts though. Two brands of low-cost components (some of which I know are supported by ArduPilot) are Matek and Kakute, and these are available from distributors like getfpv and teamblacksheep.
One example, the Matek F405-Wing, has a large presence on the forums in threads like this one: E-flite Convergence Using Matek F405 Wing

Thanks for the advice there, I might try this FC next.
as for the airspeed, I have given up on the pixracer clone for now and installed a new holybro pixhawk4 which i had in a box instead.
The airspeed and gps works (they are on separate i2c ports) but the system gives no pwm output at all!
I will start searching for any existing threads related to this issue.

Digging up this old thread, to ask a question that is pretty blatant to me but haven’t found any indication of an answer online.

The sensor is supposed to be factory calibrated against temperature. In fact, one of the calibration coefficients is the pressure offset (C2).
If this is so, then why do we need to calibrate it on every boot?

To be fair, ARSPD_OFFSET values on this thread have been reported as high as around 100, and in my experience I get as high as 210 (Pa) and these are withing the accuracy spec. of the sensor (1.25%Full Scale Span).

But if it is so, I shudder to think what this sensor would spew out if the calibration coefficients are not used.

Do you find it normal for the sensor to have so large zero offset, given its advertised calibration?