How to change Voltage to Pressure or Pascal (Pressure) in Labview

[SimpleSam]

Hi, I have experience in Dasylab, and I know that it is possible to change measurements in the graphical readings . What I want to do is to convert voltage readings to pressure (either PSI or PA- preferrably PA). Does anyone know how to do this? Thanks

[CJ_Butler__DASYLab_Pro]

I see an Express VI for scaling. It's simpler than DASYLab, but does offer y=mx+b, and a table of reference points.

There was an example using it, too, when I searched for examples. 

[pjr1121]

Making conversions such as this should be device dependent.  Check the manual of your gauge to determine the responsivity (Voltage / Pressure).  If it's linear, you can accomplish the conversion with some simple math.  If it's non-linear, you may have to utilize a look-up table or reference file which contains the conversion factors.  Alternatively, if you are using a force gauge, you will also need the device area to convert from force to pressure.

[SimpleSam]

Thanks CJ_Butler. I take it you are referring to the Formula (Signal Express VI)? Also just wondering if you or anyone else knows a formula for converting voltage to Pascal (pressure)? Thanks

[pjr1121]

As I mentioned before, the actual conversion you have to perform is device dependent.  One may be linear with 1V/1Pa with another being 0.113V/20Pa or perhaps quadratic with PA = 0.002+0.1V-0.0009V^2.  There is no universal answer we can give you.  If you tell use the device you are using to measure the pressure, we can try and help further.

[SimpleSam]

hi, thanks pjr1121 i am using force-pressure sensors

[pjr1121]

Ok, now what specifically are you using?? who did you buy it from? what model number? is there a manual??  Force pressure sensors vary from measuring the weight of semi-trucks to using peizo electrics to measure near nano-gram resolution of very small items.    

[SimpleSam]

I am using the Force Sensitive Resistor - Square, (from "CoolComponenets") the link for it is below

http://www.coolcomponents.co.uk/catalog/force-sensitive-resistor-square-p-566.html

I have also provided a link for the manual below. The information of the square FSR is on page 12

https://www.sparkfun.com/datasheets/Sensors/Pressure/fsrguide.pdf

Thank you

[crossrulz]

How are you sensing the pressure?  That sensor just just changes resistance.  I would suggest the Voltage Divider given on page 18 of that guide.  You can then work the equation to have the FSM = X (I don't feel like doing the math right now).  From there, you know the conversion from resistance to pressure.  Combine the equations to go from output voltage to pressure.

[SimpleSam]

I'm not particulary goodat Maths..can you pleasetell metheequation, when you areready. Thanks