USB 6009 Amp

[TopperO]

Hi Everyone,

I have a small project working with an Instron model 1000, trying to set-up a teaching demo. I was able to identify an analog output related to force from the machine, that outputs a voltage of 0-500 mV proportional to the load.

I am thinking of using a NI USB 6009 to read the signal and send to labview for plotting and saving the data. But, I am concerned the signal may be low and I am thinking of using a LM 321 Op Amp to build a differential amplifier to boost the signal, and maybe also a noise reducing circuit. Does anyone have any experience if the LM 321 can operate off the USB 6009 output voltage, or would my idea lead to more noise and a messier signal?

[johnsold]

Even though your application does not require a differential input configuration, you could switch to the +/-1 V range in differential mode. That gives you about half a millivolt resolution or about one part per thousand of the full scale output of the Instron.  I doubt its accuracy is better than 0.1%.

The LM321 could be used but I doubt it would be much of an improvement.  The gain would need to be kept to about 5 to stay within the apparent output swing range. The 2-7 mV of input offset would also add to the errors. The 5 V power available from the USB-6008 is derived from the digital power of the USB and is likely rather noisy. 

I would stay away from an amplifier for this situation.

Lynn