We do a lot of pitot calibrations and measurements. It's hard to beat a Rosemount 3051. Like everything else, it must be calibrated. Don't presume any transmitter is accurate until it's calibrated.

The most sensitive of the Microswitch pressure transducers (sealed, plastic, robust device about 50x25x12 mm in size with two pressure ports) are inexpensive and at very linear in the calibration in terms of Pa/V. From memory around 100 Pa/v when you calibrate with screw-driven syringe, or similar. Good luck. LC.

Thank you profesor Leighton Cochran for the answer, did you mean a honeywell sensor?

Yes. Martha. Honeywell and Microswitch merged in some fashion years ago, I think. But you are right the parent company is Honeywell I believe and they sell the transducer to which I am referring. They come in various sensitivities and you need the one with the smallest range for BL wind tunnel applications. Even then you will only be using the bottom 10% of the positive and negative pressure range. Also, note that this instrument also has a good dynamic response to pressure fluctuations; not just for mean work as say a Prandtl Pitot tube. Last time I bought one they were not expensive; about 40 US$, from memory. Good luck with your research. LC

Dear profesor Leighton Cochran Thanks for your recommendation, we were able to buy the honeywell differential pressure sensor, but I would like to know if, when you used it, you had problems with noise and how it decreased. Also on the equation to convert the voltage to speed, did you clear the pressure of the equation that appears on the data sheet? What is happening is that when I apply the equation I do not find the speed at zero. Thank you so much

Martha. My memory is that there was very little noise associated with the signal from this device. Perhaps you have some other electrical noise source in your lab. Anyway, the signal should be low-pass filtered before you pass through the A-to-D converter and computer. As you are using this for a Pitot tube that sample rate and low-pass filter settings can be quite low. Remember to have good separation to avoid Nyquist Frequency issues; although for mean Pitot data this is less of an issue.

I am unfamiliar with the equation you refer to on the data sheet, but it sounds like you need to zero the voltage before collecting data within a still tunnel. Suggest you develop your own calibration curve (a simple linear relationship is all you need) using a screw-syringe, tubing, and voltage sample program. You should end up with a very linear relationship. In my case the coefficient was 133 Pa/V. But each transducer is different and you need to measure your own calibration relationship. Obviously the line must go through (0,0). Cheers. LC