pressure data acquisition from an airfoil

[Maruthi]

we are trying to design a data acquisition system using
NI Labview and using Omega Px-137 Pressure sensors.The air flow
tunnel is obtained from Plint systems.,UK.The airfoil in the flow
tunnel has these inbuilt pressure sensors [12 of them]which in the
experiment are connected to the 12 pressure tappings of the multi
tube water manometer. we have obtained the readings which are
pretty much the same as the readings in the manual that
accompanied the system.
Now we are trying to automate the experiment using
Labview. we have two port pressure transducer PX-137[onto
which 2 of the pressure tubes from the airfoil go at a time...so
changing the tubes 6 times we get data from all
the 12 tubes], connecte
d it to the data acquisition board
[PCI 6024-E]and are trying to obtain the data. we are running the
data acquisition channels in differential mode taking a pressure
range of 0-1 PSI corresponding to voltage output of 0-18 mv[with
12 V excitation]. But the data that we are obtaining from the
Labview program are no way closer to the desired data.
From my personal point of view I guess there is some
problem configuring the data acquisition channels on the set-up.
Could you please suggest me if I am going right with the
assumption of a pressure of 0-1 PSI, differential mode set up in the
experiment.
I appreciate the support
Thanks a lot
Maruthi

[Filipe A.]

Maruthi;

The problem might be related to a wrong choice of the input gain of the DAQ board. Since your data input voltage range is quite small, you need to apply a gain on the DAQ board so the input signal is amplified to best fit the DAQ board input range of 0-10V.

In Labview you can change the input level parameters at the AI Config.VI to best characterize the voltage range of the input signal.

After that done, run the VI and don't do any unit conversion. Acquire and show the voltage level that the sensor is delivering, and see if that voltage value make sense.

If it does, you can configure a Virtual Channel in MAX to convert the voltage reading to the desired physical unit, and then use the Virtual Channel created as the input channel in Labview.


Hope this helps.
Filipe A.
Applications Engineer
National Instruments