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automatisation of measurement

Question asked by jjjackson on Mar 8, 2014
Latest reply on Mar 14, 2014 by jjjackson

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Hello we have in our laboratory an N6762A module and we want to use it for Current-Voltages caracteristiques. we have a program that set voltage and measure the corespodant current of the DUT. We want to modifie it to automatically generate values of voltages and measure the different current to have the I-V characteristic. I tried the for range but it did not do the job. I please need your help!!! thanks.

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Mike Mar 10, 2014 5:51 AM
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I think you are going in the right direction using FOR RANGE - that's what comes to mind given your explanation.

For the output, assuming you are simply returning a number from the module, try putting it into a LOGGING ALPHANUMERIC so that it captures all of the output values.

If that doesn't help, why not attach a copy of your program or a screenshot which might give us a better idea as to what you want to achieve and where you need assistance to get there.
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- jjjackson @ Mike on Mar 10, 2014 9:42 AM
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  Thanks for anwser me. In fact i attached the program. I took it from the sample program AgN6700b and i tried to modified it. So that we do not have to enter the values of current manually. In the set voltage whent i enter value of voltage it give me in output the corresponding current of the DUT. but i do no know how to génerate a plage of voltages values for examples from 0V to 6V with a step to have an I-V caracteristic. I tried the for range and it do not work as i expected and for the record it just record one values of both voltage and current many time.
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  - AgN6700b3 - Copie.bak31.7 KB
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  - Mike @ jjjackson on Mar 10, 2014 3:28 PM
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    The thing you need is a data collector - find it in the menus Data -> Collector. I have attached a simple example - this uses 2 Collectors ( which is not the only way to do this, but to keep the concept straightfoward ;-) ).
    
    What this does is to take each data element as it arrives and then when the loop finishes ( indicated by a signal out of the bottom pin of the FOR object ) it outputs them all in an array.
    
    The X vs Y plot then has its X input fed with an array of voltages and the Y input with a set of currents.
    
    Notes:
    Your 'Read Channel 1 Output Values' UserObject has an input that is not used... I would recommend removing that
    
    You have a 'build record' object - if you wish, you can put that before the Collector - the output will then be an array-of-records
    
    in my program, the 'ONLY FOR DEMO' object is only because I don't have your hardware, so it is used to store the set voltage
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    IV Characteristic.vee4.9 KB
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    - jjjackson @ Mike on Mar 11, 2014 12:04 AM
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      Thanks Dear Mike,
      I will tried it at the lab today and i will lets you know. For instance we have and N6700B with the module N6762A. It is the one we want to automatise for I-V characteristic. I show you and example (attached file) of how i changed the program at home this nitgh after read your answer.
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      AgN6700b3 - Copie.vee27.6 KB
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      - jjjackson @ jjjackson on Mar 11, 2014 4:27 PM
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        Thanks so much Dear Mike i tried the program that i show you and it work. even for the record and the output file. despite the fact that it did not draw the curve instantanuosly but is ok for us that it do the job.
        We wanted to know if it could be possible with our N6762A to the capacitance of a device or the impedance. because we do need also to have Capacitances-Voltages curves and realpartZ-imaginarypartZ. For electrical caracterisation.
        thank you all
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        Mike @ jjjackson on Mar 12, 2014 1:31 AM
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        I think the answer to that is 'it depends' - mainly on how large your capacitance is. You could ask for a step change voltage output and then ( say, using a FOR CYCLE ) monitor the change in current and work out the capacitance from the curve. That's not ideal though, because the timing of FOR CYCLE is determined by the computer, and PCs are not designed for that sort of timing ( they are not accurate for short-term timing )...
        
        What time constant ( C x R ) are you expecting?
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        jjjackson @ Mike on Mar 12, 2014 11:16 AM
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        Sorry dear Mike i do not understand you i really dont know which of this time we weed. We want to know how to generate an altenative voltage that we can use for impedance and capacitance measurement. We have an impedance meter but its damage so do not give good result know. If it is possible it will help us a lot.
        thanks
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        Mike @ jjjackson on Mar 13, 2014 2:16 AM
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        You cannot measure capacitance directly with your power supply module, so what measurement principle do you intend using?
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        jjjackson @ Mike on Mar 13, 2014 3:49 AM
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        We want to caracterised métal-semiconductor jonctions. So we would want to evaluate the potential barierre the ideality factor and the level of concentration of dopans in our jonction. We would have wanted to draw 1/C2=f(V) to deduce some of those parameters. I dont know if there is another way to hace them.
        I would have another probleme please. I want to know if our N6762A perform measurement in the negative part. Because went i connect a resistance, the I-V caracteristic in the negative part is a line close to 0 while in the positive part its ok. Event for some diode that we have tested. The program doesn't give results in the negative part.
        thanks.
        
        Edited by: jjjackson on Mar 13, 2014 4:44 AM
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        N6700b-CV.vee28.4 KB
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        Mike @ jjjackson on Mar 13, 2014 4:44 AM
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        Wow this is getting involved!
        
        > {quote:title=jjjackson wrote:}{quote}
        > We would have wanted to draw 1/C2=f(V) to deduce some of those parameters.
        
        I don't understand that, unless you really mean that the capacitance is a function of the voltage? Or did you mean V = f(C,t) in other words the voltage measured will be a function of the capacitance and the time elapsed (a) from a change of compliance voltage and (b) the PSU is set to constant current?
        
        To address your second question, you'll need something like the Agilent N6784A which is a 4-quadrant device to allow you to explore the negative regions of your device.
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        jjjackson @ Mike on Mar 13, 2014 5:41 AM
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        sorry dear It may be a problem of writing. We have a relationship betwen the capacitance and the voltage. It like One over the square of the capacitance wich is proportional to the applied Voltage and the schottky barrier. We have and old impedance meter wich give us capacitances values in function of the voltages. but its very old and dont give good result anymore.
        I hope you understand me this time.
        So thanks for your help and im so sorry for my english im not so good in english.
        thanks and thanks!!!
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        Mike @ jjjackson on Mar 14, 2014 2:48 AM
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        > {quote:title=jjjackson wrote:}{quote}
        > We have a relationship betwen the capacitance and the voltage. One over the square of the capacitance wich is proportional to the applied Voltage and the schottky barrier.
        
        Yes I understand that but I was trying to get to the measurement technique. Something like: (1) apply power ( at constant current, I'm assuming ) (2) measure the voltage as it rises... is that right? Or do you really need an AC source to measure the capacitance ( which is what your impedance meter most likely uses ) ?
        
        Don't worry about your English - it's very good and I can understand you :-)
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        jjjackson @ Mike on Mar 14, 2014 7:46 AM
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        Our impedance meter surely work in AC. but if it could have been possible to make the voltage varie may be we could try to measure impedance. but its probabily impossible with our N6762A. So may be we would continu with our impedancemeter. So thank to your regard. It will serve us for I-V caracteristic even if its just in the first quadrand (I,V>0) we dont have choice for the moment. I ask today for the price of the N6784A and its so expensive for us. The university will take a long time to provide it to us.
        Thanks you again
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