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

[pjr1121]

His voltage is increasing with increasing force, it's just listed out of order in his post.

[HEAPO8]

I'm going to use these results for now and then improve on them later. Now is it best to use a Polynomial curve for the calibration curve? Or can I just do a linear line (for the equation)?

[camerond]

Whoops, I need to clean my glasses. I could have sworn ...

Cameron

[HEAPO8]

Sorry Cameron, the results were not in order. Okay,  is it best to use a Polynomial curve for the calibration curve? Or can I just do a linear line (for the equation)? And how can I finally put this in my code? lol

[camerond]

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@HEAPO8 wrote:

Sorry Cameron, the results were not in order. Okay,  is it best to use a Polynomial curve for the calibration curve? Or can I just do a linear line (for the equation)? And how can I finally put this in my code? lol

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At this point, it's your call. And all you have to do now is just write your manually-derived transfer function into LabVIEW code (use the Numeric palette).

Cameron

[pjr1121]

Do not use a linear curve.  You already know from the manual that the response will be non-linear so using a linear curve will only increase your error.

[HEAPO8]

okay I'll use the polynomial one. Okay guys I'm nearly there now- I'm sure this step is easy, but I still need help with regards to the number pallete. which one do i use to put my transfer function in? I'm just 1 step away, please help! Thanks

[pjr1121]

Build you function.... the number pallete is math operations.... plus, minus, divide, etc... just build an equation by wiring the ones you need in the correct order.  You CAN use math scripts to just write out the equation but this isn't complicated enough to require that.

[HEAPO8]

do i use the "number constant" to enter the numbers I want to use for my equation? If so how can i represent "x"? And what does the E represent in the numeric panel? The equation is in the excel file attached and is below.

-3E-0.5x squared + 0.0266x +2.0289

[pjr1121]

yes, use number constant for your coefficients.  the "E" is a scientific notation replacing 10^..... so 3E-5 = 3*10^-5

Before you continue, examing your data again.  You have two forces which both read 5V.  this likely means that you've exceeded your maximum voltage and therefore shouldn't include the large numbers in your fit.

If 5V is your maximum voltage, only include force measurements up to 4.5V (You never want to hit the maximum).