Lebow-Daytronic Loadcell with Labview

[DRAYTON]

Dear, I have a problem for my thesis. I have to measure a signal with a DAQ-card NI 6024E. First of all I will explain the test : a Lebow (model 3167) load cell (torque meter)  and Daytronic (model 3170 to read torque)  measures the torque of an engine and sends a signal (in the form of voltage 10mV/Nm) to a NI CB-68 LPR connector. Through a 68 avaricious cable SHC68 NI-68-EPM, this signal be transferred to the daq card (dev1/ai0) . ( see attachement for loadcell and daytronic)
If I measure the voltage on the connectorblock is this one /hundredth of the  torque (example: 10Nm corresponds to a voltage of 0.10 V on the connector block.)I have made a simple program in Labview (see attachements).  I read on the computer (in labview ) always the same voltage (this is 0,68V of sometimes -1,25V). The voltage on the connectorblock changes when the torque changes but the voltage i measure with the daq-card don't change. I have done everything but it is enough the same . Can someone help me please I'm going to be really crazy. I have done everything i changed the parameters in MAX made an other program in labview but not solved. I am using Labview 8.0 and MAX 4.3  the parameters are :  NI-daqmx Task ->Analog Input -> Voltage -> dev1/ai0-> as range min 0 max 10V i have also tried mv ) samples 1000  rate 1000  continoues sample also tried finite . can someone help me ? what do I wrong? See program as attachements i only get a line on 0,68V and somethimes -1,25 / I am using now try version of labview (enough 25 days)  Thank you - (Please help me i have no much time )

[aeastet]

Try this.

[RavensFan]

One thing I notice is that you say you are connected to Dev1/ai0, but your LabVIEW code is using Dev1/ai1.

Message Edited by Ravens Fan on 02-20-2009 02:42 PM

[aeastet]

You will still have to scale the signal but the voltage that you see should be voltage. The other things that I would check is how you have your analog input setup. Yo will need to understand te difference between RSE, Differential and NRSE signals and how to connect them. This is set up in NiMAX.

Hope this helped.

[RavensFan]

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aeastet wrote:
Try this.

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Aeastet, your code has a serious problem.  You are appending new data to an array every iteration, but sending that array to a waveform chart.  Waveform charts already have a history, so you will have exponentially growing repeat data.

pt, 1

 then pt, 1 and 2

then pt 1 and 2 and 3.

 pt 1, 2, 3, 4

After 4 iterations you will have 10 data points on your graph.  N iterations will have n x (n -1) data points

[DRAYTON]

thank you for the reply ;

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aeastet  

 i am using 8.0 its possible to save as 8.0 i can't open it.

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Ravens Fan  i know i have chosen on the program dev1/ai1 but its ai0 i have tried everyting but i can't solve it

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I have also chosen RSE, NRSE and differential ; i don't know the difference between it ; but it's not the correct signal i receive => i get only 0,68 and somethimes -1,25v

[DRAYTON]

plaese can you save as 8.0 ;

[DRAYTON]

please can you save as 8.0 ?

[RavensFan]

Here is his VI in LV8.0.  I added a comment about the problem with the way the build array and the waveform chart were used.

[Michiel_H]

Please check the following article on the differences between wiring methods en considerations to take:

http://zone.ni.com/devzone/cda/tut/p/id/3344

If I get it right, at this moment, the signal is connected differential, so make sure you select this as the input terminal method. Otherwise, I see no problem with the (original) program itself. 

Did you already try reading on another channel? When reading the signal in MAX using the test panels, do you read out the appropriate voltage? If not, try if you're readings are right when attaching a simple power source (small power adapter or regulated power supply...) with a known voltage to the card to see if this works. I suspect the problem to be a driver or wiring problem rather than in your program.

You might also try reinstalling the DAQmx driver with the latest version available for LV 8.0 (8.7.1). You can find it here:

http://ftp.ni.com/support/softlib/multifunction_daq/nidaqmx/8.7.1/NIDAQ871f3.exe