Convert Voltage to Pressure

[KowdTek]

I've just looked at your device datasheet,  it supposed to give you 0.1-5.1 output. Forget the 249 ohm load. Now, on 1121 check your excitation setting. Often they are not in default, so set it up to "voltage". Check the datasheet.

[tacky]

Hi KowdTek

  I just read about that in the manual.  I will check to see if the jumpers are set correctly.  Also, in the DAQ assistant where I acquire an analog signal...  should I select voltage or custom voltage with excitation?

[KowdTek]

It's hard for me to tell because I've never used both device but it won't hurt you to try both. Whichever works for you, but I usually set just the voltage...

[tacky]

Hi

  Fairly new to labview so please bare with me. I have few more questions.   concerning pressure tranducer readings should I scale volts to pressure from the DAQ assistant using custom scaling or write a code in the VI? Sometimes numbers fluctuate constantly,wondering if some filtering is needed in the VI.  Last question is when splitting signals from the DAQ assistant is there a way to tell which signal is what?  I have temperature sensors also hooked up to my terminal blocks. Thanks!

[KowdTek]

@ tacky, it's fine to use scaling that can be set at DAQ Assistant, also you could tweak the samples to read and rate settings. As for how to identify which signal you are reading, use "index array" then wire the input channel right to index port.

[Dennis_Knutson]

If you are going to use dynamic data, then you have to be careful with the Convert From Dynamic Type. The example above assumes that there multiple channels sampled a single time. That might not be a valid assumption. That's just one reason why I avoid dynamic data. It's impossible to tell the actual data type visually

To the original question, if the split signal function is used, then the order of the outputs is the same order as the channels in the DAQ Assistant. If you are going to use something like the DAQ Assistant, then keep the dynamic data throughout and avoid the Convert From Dynamic Type unless you are very sure what you are doing.

[tacky]

After speaking with NI Tech support, the SCXI 1327 TB with a SCXI 1121 module cannot provide enough excitation for the pressure transducers I am using.   In DAQ property the excitation value stays at 3.33 and comes up with an error if any other value is put in. Only 3.33 or 10V is recommended.  I bought this stuff so that I wouldn't have to buy an external source which he suggested.  Is external the best way to go to provide excitation? or should I have bought press tranducers with 3.33 or 10VDC?

[tacky]

Hi

  concerning the excitation voltage needed for the cole parmer transducers, I changed to a pair of omegadyne transducers that require 10Vdc. I change jumper settings in module and Measurement&automation and think this will work better than the cole parmer. I think I can figure it out from here with all of the previous suggestions that have been given! Thanks!

[SOMA76]

I am using ICP pressure sensor (model 113A24) from PCB Piezotronic. I have attached the sheet. With the defined range of -5-+5V and the pressure range of 0-6895 KPa I have calculated

m = 689.5                C = 3447.5             for  Y =mX+C

I have attached the sensor data sheet. Can someone recheck my calculation based on the provided data from manufacturer. 

[johnsold]

Those numbers appear to be reasonable.  It is interesting that they specify the sensitivity as 0.725 mv/kPa, while the span calculation gives 0.6895 (although it is within the +/-0.25 mv/kpsi tolerance).

Lynn