How to cheaply measure and plot low current over time while sourcing a constant voltage?

[Rhydo]

Hi!

I am working on a research project which involves me building and characterizing transistors. I do not have access to expensive current sensing intruments but I do need to plot the current (in micro-apms) over time at a constant source-drain voltage (200 millivolt) and see how this current changes when I manually apply different gate volatges.

I am new to the field of measurement and characterisation. I am also low on financial funding so I was hoping that someone here can guide me towards the right Data Aquisition System and the appropriate LABView code to do this measurement. It would be a great help.

I apologise in advance if I sound way out of my depth in this field. But I am in dire need for some guidance. Any help would be HUGELY appreciated.

Thanks in advance!

[Dennis_Knutson]

You have posted to the wrong board. Measure is an obsolete add-in for Excel. You can click on Options and request that the moderator move your question to either the LabVIEW or Multifunction DAQ board. I would also recommend you contact your local Sales Engineer to discuss your needs.

[Rhydo]

Thankyou for notifying me. I didn't know of this since I am new here. I have notified the moderator.

[SteveD123]

Some suggestions:

1. Buy "The Art of Electronics" by Paul Horowitz and Winfield Hill. Read the section on instrumentation amplifiers. Look at the Analog Devices website and chose a suitable part.

2. Build 2 instrumentation amplifiers. Make sure they have very high impedance input stages. Put 1 across a current sensing resistor in the drain connection. Put the second between the source and drain.

3. Build a circuit that monitors the output from amplifier 2 and adjusts the source-drain voltage to maintain the required constant 200 mV.

4. The output from amplifier 1 can then be fed into the cheap recording instrument of your choice.

I am afraid that National Instruments is the wrong place if you want anything "low cost". The benefit of National Instruments hardware and software is that it offers unrivalled integration and support. That comes at a cost.