DC measurement and generation

[elahetal]

HI Matt,

Thanks a lot for your input. I solved my problem before your input and it works now. Now, I want to increase the measurement accuracy, so I attach my latest code and I will thankful if you help me to increase the precision. I have checked the results with experimental results and they are slightly different, the volatge varience from correct value is about .2 volts and I prefer more accurate measurement. Do you have any suggestion for me?

To describe my code, my desired sequence for measurement and generation is as following:

Ao 1 in outer loop, AO 0 in inner loop THEN AI 0  ----> AI 1 is supposed to do measurement once after the A01 but I have synchronized it with the other AI and it works for me in this way as well.

Thankssssss 

[Mr.F]

Hi Elahetal,

What experimental results are you checking against? I may have missed it in your earlier post, what DAQ device are you using? Do you have a hand held DMM to check against?

[elahetal]

I use PCI 6052 (Eseies). yes I have a hand held DMM. the channel outputs are measured with DMM. they are correct but the measurement values are not accurate. 

If I said I have checked the result with my experimental results, I mean that I have done some test on my circuit( and DUT) with stand-alone equipments and then I have run my circuit using my LV code. the result is correct but I think the problem is that when I want to generate DC voltage, due to some noises , the output is not clean (I can see this even using the DMM), is there anyway that I can increase the accuracy of the measurement .  

[Mr.F]

Does your PCI card measure .2 V off when connected to a known voltage source, like a battery? It’s possible your card is out of calibration, although .2V is a lot. When was this card last calibrated? What sort of “noise” do you see on the output?

[elahetal]

HI Matt,

Thanks for following up.

yes it is, if I connect it to a known voltage source, it measure about .2V off. I didn't mean it a real noise, I mean if I use a stand alone power supply and set it for the desired value for example 5 volt, and connect it to a precise DMM, the output oscillation if I connect a known voltage of 5volt to AI and measure it by 1 sample software-clock analog measurement  or even test in MAX, this oscillation is about 40-50 mv.

Honestly, I have borrowed this card and do not know when it has been calibrated last time.

BTW, if you had a look at my last VI, is it OK, I mean as a person who is familiar with LV, is it seems OK? 

[Mr.F]

What happens when you run a test panel? Acquiring a known constant voltage you will still see spike but they should be minimal, you can see in the picture I’m seeing spike less than 1 mV.

 

Also, can you disconnect your external connections and run a self-calibration? This should help remove some of the offset you are seeing. You can self cal your board by right-clicking in Measurement and Automation Explorer on your card and select “Self Calibrate”.

As “A person who is familiar with LabVIEW” your code looks OK at first impression from an architectural perspective. I would remove the extra box decoration around your writes and reads and, if you’re using LabVIEW 8.6 or LabVIEW 2009, you can select the block diagram clean up tool to reorder your VI and make it more readable. Generally it’s a good idea to minimize bends in wires and the number of times wires cross over other wires to make your VI more readable. This won’t affect the functionality of your code but makes looking at the code, and troubleshooting a lot easier.

[elahetal]

Thanks Matt, I do calibration and keep you posted if I have a better results.