Convert Voltage to Pressure

[rpedman]

I am using a PMD-1208LS device from measurment computing and have all the drivers installed, I am unable to use the MAX program to detect any devices for DAQ, however, I can use the VI's supplied with the device so I can get an analog input reading from my pressure transducers. I need to know how to convert my input into a usable number (i.e. Inches of Water) on my graph and display. I have a 24VDC power supply operating the transducers, and the transducers are 0-5VDC output.

[lmtis]

What pressure transducer are you using?  Does the manual for it give the voltage to pressure conversion?

[falkpl]

MAX Is the driver for NI products so MC Boards will not show up (as far as I am aware).  If you are getting a voltage, you just need to look up your calibration scale from the transducer producers manual.  Hopefully it is linear and there is not much ot do but put in the pressure unit/volts and the volt offset into y=mx+b.

[SLee2004]

Pressure transducers output a raw signal that corresponds to a value in an engineering units.  These vaules are usually imprinted on the pressure transducer (i.e. a -15 to 15 PSI operating range with a 0-5V output).  The scaling is usually linear, which means you have to use y=mx+b equation for scaling the sensor (m = span, b = offset).  You have to find the span and offset (calibration values) using the range limits and output limits.  Scale the signal in LabVIEW using the calibration values where "x" is your raw signal and "y" is your usable signal.

[Matthuz]

To do the convertion from a sensor voltage to pressure I some times use the lpolynoimical interpolation vi... I attach an example of a sensor 0.5v - 4-5v to 0-150psi.

I too use the same vi when the sensor isn't linear, some temperature sensor that I'm using result to have a very nonlinear curve, so I simply charge the input and output

points on the array tables and works perfectly.

I don't know if this is the best way to do it...but it works for me

[KowdTek]

I know this is an old thread however, I want to apply the same method as u used but I can't find the polynomial interpolition vi.

 ------------------

Found it!

Thanks.

Message Edited by KowdTek on 02-13-2009 12:08 PM

Message Edited by KowdTek on 02-13-2009 12:09 PM

[tacky]

Having similiar issues with converting voltage to pressure.  I am supposed to get a 0.1 to 5.1 Vdc output but I think I am getting results in mA.  I have read the all of the post pertaining to using y=mx+b and I can figure that out but I am not getting correct readings.  I am using cole parmer model (12 to 28 VDC; 0.1 to 5.1 VDC output) Pressure range is 0 -3000 psig.  Can someone help me!

[KowdTek]

can you post the exact model #? i'm using few from CP. you might want to post ur code too.

[KowdTek]

Put a 249 ohm resistor across the output and it will give you a .1 - 5.1 vdc out.

Goodluck bud!!!

[tacky]

thanks KowdTek

  The cole parmer pressure transducer model is EW68074. I am using a SCXI 1327 T-Block (voltage attenuator connected to SCXI 1121) which I believe is supposed to read voltage directly. Should the pressure tranducer return the output in mA or volts?  Unless the SCXI 1121 model is converting back to current then I am doing something wrong!  Should I bypass the attenuator to remove the 100:1 divider at the beginning?