how to achieve current "measurement" autorange ?

[4135SMU]

Hi,

  we got three NI PIXe 4135 SMUs and we are using them to measure I-V curves of our device(diodes, transistors...).  we want to output/sweep voltage (like from 0-10V) and measure current; we know the maximum current which could flow through our device, for example 1mA, but the current reading may vary , it can be as low as 1pA, or as high as 1mA. I wonder if anyone has developed a Labview code to achieve the measurement autorange function. From my earlier discussion in another board, I found out for NI's SMU, the measurement auto range can only be done through software. I was referred to look at the "advanced sequencing: example vi in NI DCPower driver package. but what I found out is in that example, it is talking about autorange for output. I know set the right range for output is also important, but the challenge is not even close to the one of measurements because when you output, you know exact value you need to output, but during measurement, you didn't know you will face 1pA or 1mA except you know it is no more than 1mA.  I wonder if someone also give it a thought and developed some code.

regards,

Ted

[Misbahd]

Hi Ted,

Have you looked through NI's help documentation on SMUs?

-Misbah

[ChrisR.]

I don't have an answer for you, but I'm curious why you sweep voltage instead of current.  If you were to sweep current, the available autorange function would work for you, and the voltage measurements could all be made in one range.  That's what I do to get the IV curve of a diode.

[4135SMU]

from what I learned so far (talking to NI engineer and other users), NI's SMUs could not achieve auto-range by hardware, it has to be done through software. They have a good idea to do auto-range for output, but not on "measurement". I think this may be a common issue and other users already run into it and solved.  that is why I am here. 

ted 

[4135SMU]

let's say we have some transistor like device, which you drive them by voltage and our collaborator wants to duplicate the real situation. 

[HSD]

The latest version of NI-DCPower supports measurement autorange that is done on the hardware.  The feature currently supports the 4135, 4136, 4137 SMUs.

[shiksri]

Did anyone got a solution to this?

[santo_13]

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@jame24hour wrote:

Thanks for the update! It's great to hear that the latest version of NI-DCPower supports hardware-based measurement autorange for the 4135 SMUs. This should simplify the process significantly. For those still using older versions, could you provide any guidance or workarounds for implementing autorange via software? Your insights would be very helpful!

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A software based auto-range will be using the logic,

Measure in highest range (based on application)

If measurement < 10% of present range:

   Configure the next lower range

   Measure

Else:

   Return Measurement

I quoted 10% as an example, this threshold depends on the accuracy of ranges of the instrument and the overlap.