Pressure sensors

[rblilja]

Hi

I would like to know peoples opinions regarding pressure sensors in the purpose of measuring speed and altitude. Which sensor is your favorite, and why?

The only requirement is that the sensor is to be powered by 5 volts or less.

Thanks!

[rbeall]

most of the work I have done with Pitot statics has been with freescale sensors (pretty sure motorla took them over or something). They are 5 volt sensors but you have to condition them with opamps. I havn't seen any (havn't looked all that hard) sensors that tailored for an out of the box solution. I just chose what I did because you can choose the range and resolution (knowing your a2d res) that best suits your profile.

[Peter Seddon]

I have used the Intersema MS5534 for altitude measurement and it seems to work ok but the SPI interface took quite some time to get working properly.

I am about to use the SCP1000 for altitude measurement as I am hoping it has an easier interface and it is supposed to offer greater accuracy.

regards Peter

[vector_vortex]

Hope RF HP03D, about to use it for a vario (device for measuring vertical speed) so it'll be a good test of it's performance, it's a very cheap integrated unit.

Joel

[rblilja]

Thank you all for the replies.

The HP03(D) appears to be interesting since I personally prefer I2C in the purpose of MCU-Sensor communication. Still the SCP1000 looks tempting… Sadly the break out board version is pretty expensive.

Joel, may I wish an update regarding the HP03D’s performance when you have reached any conclusions?

However, since I’m interested in both measuring altitude and airspeed, the freescale sensors may be the logical alternative. I have placed a sample order on MPXH6115A (altitude) and MPXV5010DP (airspeed).

Regards Lilja

[rbeall]

Know that you are going to have to condition them. I think I calculated once just using them by themselves with a 12bit a2d and it was somewhere in the 100ft resolution between bits. Obviously not useful. Amp them suckers up and you can get inches of resoltion! Very amazing to see those little things measure inches of pressure change. Of course it saturates at like 150 feet at that resoltion so you have to decide what working range works for you.

[rblilja]

@rbeall:

Ok, I guess that you can't have everything, as usually. Did you use any low pass filters? I'm thinking of a second order Butterworth filter in a nice Sallen-Key configuration. Where should I put my cut of frequency?

[rbeall]

I am actually working on noise reduction today. I used some isolation caps at the inputs to the sensors. But other than that I have nothing and it looks pretty decent. I added a single pole first order LP and that seems to be just fine. As far as COF....I just fiddled with the gains until the performance was what I wanted it to be. What I have seen in literature is anywhere from 20-30hz. But like I said I just played with it until the plots looked better.

-Ryan