NI 9237 matlab half bridge strain gauges

[ismailel]

Hi everybody,

I created under matlab a code that acquire data from two strain  gauges, each one is made of two resistances, each gauge is configured as a half bridge fixed to a beam using NI9237, the aim of my code is to estimate the applied force to the beam, my problem is that at the in the end of acquisition i do not get the expected value of the applied force, the error is about 77%, i checkek very well every single line of my matlab's code based on the instructions from the following page (http://nl.mathworks.com/help/daq/acquire-analog-input-data.html), i am pretty sure that the problem comes from the device or something like this, cause i checked the coefficients that convert strain to force under a finite element software  and the the result was as expected, somehow the output voltage that i get isn't correct.

Can any one help please :s ??

[ismailel]

Hi everybody,

I created under matlab a code that acquire data from two strain  gauges, each one is made of two resistances, each gauge is configured as a half bridge fixed to a beam using NI9237, the aim of my code is to estimate the applied force to the beam, my problem is that at the in the end of acquisition i do not get the expected value of the applied force, the error is about 77%, i checkek very well every single line of my matlab's code based on the instructions from the following page (http://nl.mathworks.com/help/daq/acquire-analog-input-data.html), i am pretty sure that the problem comes from the device or something like this, cause i checked the coefficients that convert strain to force under a finite element software  and the the result was as expected, somehow the output voltage that i get isn't correct.

Can any one help please :s ??

[ismailel]

Petite correction:

L'erreur est d'à peu près 50%

Merci 🙂

[Dennis_Knutson]

Why do you continuously post to the incorrect board?

[ismailel]

Hi,

Why don't you give me the right one?

[Dennis_Knutson]

You've already posted this question to the correct board - Multifunction DAQ. You also got an appropriate answer. Mathworks has its own website that you should post to with Matlab questions.

[ismailel]

The problem isn't a Mathlab problem but an NI one, furthermore i didn't get any useful answer until now.

[Dennis_Knutson]

You think it's not a matlab problem. You were told 4 days ago to test your device and connections in MAX. Apparently you still have not done that. You certainly have not provided your matlab code, connection information, or details on the strain gauges.