Analog Input voltage readings into USB 6008

[Dustin_D]

Hi VJ, 

Would it be possible for you to try a differential measurement to see if you get better results?  You may have a grounding loop due to the configuration of your sensors.  Let us know!

Regards,

[Dustin_D]

Hi VJ,

Can you try a differential measurement to see if your results improve?  I'm suspect of a grounding loop that may be occurring and causing some unexpected behavior. Let us know!

Regards,

[VeeJay]

@ Dustin. You mean, supplying the inclinometer voltage as a differential measurement? positive to ai0 and negative to ai4?? Problem is the circuit is all soldered up and channels allocated. I will see what I can do though. But, please confirm whether I am understanding it right.

Thanks!

Vj

[Dustin_D]

Hi VJ,

I think you should try a differential measurement with each one of your sensors separately to see if it improves your results at all.  I'm suspicious if you having some sort of grounding loop or other grounding problem.  A differential measurement would surely give you accurate results if your sensor setup is correct. Let me know how it turns out!

Regards,

[Dustin_D]

Hi VJ,

Please disregard all of those posts, something went a little silly on my end and my browser was showing a cached version of the page.

You won't be supplying as a differential measurement, you will just be measuring differentially, It's likely that there is a problem with your sensor setup if you are getting effects such as those explained.  Also a screenshot of this behavior would be helpful.

Regards, 

[VeeJay]

Hi Dustin. Thanks for your help ! i used differential measurement and it works. it was a grounding issue....  🙂

Vj

[crossroad]

Hi VJ,

I have a similar design to yours except that my circuit measures temperature and irridance. For my irridance sensor it outputs voltage and as for my temperature sensor it outputs resistance. To find out the resistance of the temp sensor I place the sensor in series with anothe resistor of the same value and pump 10v dc across the ciruit. I use the DAQ to meausre the voltage drop across the temp sensor. Using the voltage divider rule I manage to get the resistnave across. However, I reliased that my voltage fluctuates between 20-150mv resulting in huge change in resitance. As such, could u recomend me a method where I am able to obtain a reading like a DMM or to make the voltage reading less sensitive?

Thanks
Andy