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I-V Measurement?

Discussion in 'General Electronics Discussion' started by Twigg, Dec 6, 2011.

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  1. Twigg


    Nov 23, 2011
    Hi all,
    I'm curious what ways you can measure I-V. While working in a physics lab, I used one setup with a potentiometer connected to a constant speed motor, working as a voltage divider that varied linearly with time. The current was picked up by the vertical axis of a mechanical plotter, which moved across the plot at a constant speed in sync with the motor. That was a pretty old setup, and I doubt people use something like that anymore--at least, I *hope* they don't. Anyone know what the other methods are? I'm more interested in the way they control voltage than how they display the signal. Thanks.
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Hi Twigg,
    a pot is still a good method to control a voltage.Alternatively a D/A converter. You most probably will need an amplifier to decouple the load from the pot or DAC if you require any serious current through the load.
    Another way would be a lab voltage source where the output voltage can be set either manually or electronically e.g. by a computer.

    Depending on your application you could also turn things upside down and control the current through the load while measuring the voltage. The resulting characteristic is the same. This latter method I'd prefer for primarily current controlled loads, e.g. LEDs (it is possible to control LED current by finely regulating the voltage, but due to the very small dynamic resistance of an LED this is easily prone to thermal runaway followed by destruction of the diode).

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