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USB-6009

Hello firends,

                      I am facing problem in communicating with a load cell using USB-6009. It is a futek load cell which I am connecting through a amplifier (futek) to USB - 6009 "AI0" channel . On applying load to the cell the excitation voltage on USB-6009 input is changing ( I measured it), indicating load cell and amplifier is fine.

  

 The USB-6009 is recognized by NI-MAX and it is passing self-test everytime. But in the test panel of NI MAX I am not capturing any change in response with load application.

 

As a check, whether I am connected to proper device channel in my program  I switched of the power supply to load cell - this causes the load reading to fall; switching on the power makes the reading shoot up indicating that I am connected to right channel of my device(6009).

 

Can anyone give me any clue as to what might be happening?

 

Thank you.

 

Partha  

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Message 1 of 15
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Hi Partha,

 

Are you connecting your amplifier and USB-6009 in a single-ended or differential configuration? I would suggest you to try different wiring options and keep testing them in the Test Panel in MAX. There is a developer zone article that you might find it helpful: Field Wiring and Noise Considerations for Analog Signals.

 

Also I just want to point out that USB-6009 is not specifically designed for strain-gauge applications, therefore you might need to have your own bridge circuit, excitation source for getting a good signal and some math to calibrate the result. There are some more developer zone articles on strain-gauges: Measuring Strain with Strain Gauges and Making Accurate Strain Measurements to help your design.

 

Alternatively, if you want to avoid doing these by yourself, NI provides DAQ devices that are designed for strain-gague measurements, such as NI USB-9219 which has built-in Quater, Half and Full Bridge circuits in conjunction with excitation voltage sources.

 

Hope this helps,

Best regards,

Mark M.
Applications Engineer
National Instruments UK & Ireland
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Message 2 of 15
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Hi Mark,

             I am connecting my amplifier in differential configuration. I have actually used USB-6008 in a similar way and it works fine. Also, I am not sure, whether my USB-6009 is properly  installed - is there any way to confirm it?

 

Also, if I want to re-install the card from scratch what do I need to do? J

  

Best regards,

 

Partha

 

 

 

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Message 3 of 15
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Hi Partha,

 

The Self-Test  function in MAX should give you the correct indication if your DAQ card has any issues. So at this point, I would suggest you to do a test yourself to see if it was the problem of the system connection or the DAQ itself.

 

The test is simple: disconnect all connection currently on your USB-6009, then use a pair of wires to connect an analogue input channel to an analogue output channel on your USB-6009.

 

I've also done a simple VI for you to do the actual test that you can find in the attachment. Once you opened it, just change the physical channels of the input and the output to match the ones you are bridging together. When you run it, you should see a sinusoidal wave on the graph on the front panel.This will verify that both analogue input and output functions on your DAQ are working properly.

 

Please keep me updated on how you are doing,

 

 

 

Best regards,

Mark M.
Applications Engineer
National Instruments UK & Ireland
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Message 4 of 15
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Hi Mark, 

 

             I did the test . The 14th (AO0) and 15th pin(AO1) out from USB-6009 was connected to 5th and 6th pin ( channel +AI1-) of USB-6009. I am not able to get any sine curve response.

 

 

With best regards

 

Partha 

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Message 5 of 15
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Partha: I did not access the manual to verify pin numbers nor look at the test vi, but from your text description it looks like you tried to use two analog output channels.

I think you may need to use AO1 out and Analog Ground as the two connections to your analog input channel.

 

-AK2DM

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"It’s the questions that drive us.”
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Message 6 of 15
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Hi AK2DM,

                   Thank you for pointing out my mistake.

 

Mark,

         I retested by connecting 16th (GND)  and 15th (AO1) pins to +A1-. However, I am not getting any response.

 

 

With best regards,

 

Partha 

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Message 7 of 15
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Did you set up the proper channels to use for the test in the vi that Mark posted?
~~~~~~~~~~~~~~~~~~~~~~~~~~
"It’s the questions that drive us.”
~~~~~~~~~~~~~~~~~~~~~~~~~~
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Message 8 of 15
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Yes.  The input channel was  /dev1/ai1 and the output channel  was /dev1/ao1

 

In the input (  channels available are  AI0 - AI7)  selected "AI1" because my physical pin connections are 5th and 6th, while  in the output ( channels available are  AO0 - AO1)  choosed 'Ao1" as physical pin connections are 15th and 16th. 

 

- Partha

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Message 9 of 15
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Mark:

 

For that test program, what should the analog input text be for the differential input configuration? I don't think using dev1/AI1 will work for a differential? Does the program even set up a differntial mode?

 

Until then Partha, try using pins 4 and 5 for the test program

 

-AK2DM

~~~~~~~~~~~~~~~~~~~~~~~~~~
"It’s the questions that drive us.”
~~~~~~~~~~~~~~~~~~~~~~~~~~
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Message 10 of 15
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