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  • Author Author: tariq.ahmad
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A DIY Current Source Demonstrating Ohm's Law -- DC to Daylight 02

 

In this episode, we take a look at the shortcomings of measuring low resistances with a standard digital multimeter. We demonstrate measuring a small resistance using both the two-wire and four-wire kelvin methods. Then we build a standalone current source that will be used in conjunction with a standard DMM, allowing us to make four-wire measurements, without an expensive benchtop meter.

 

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  • Hi Derek,

    That is a really nice video with great explanations of the design and build!  I designed and built a milliohm meter with input from other element14 members some time back.  It had two ranges with two different current sources.  We had some issues originally with stability at very low resistances but worked that out.  Shabaz built a really nice version, compared it to a Keithley DMM 6500, and posted it here.  In the comments below that post, there is an interesting application involving reading the RDS value of a MOSFET.  I've since designed a version with auto-ranging and even ordered PCBs but have yet to populate and test it.

    Frank

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  • Hi Derek,

    That is a really nice video with great explanations of the design and build!  I designed and built a milliohm meter with input from other element14 members some time back.  It had two ranges with two different current sources.  We had some issues originally with stability at very low resistances but worked that out.  Shabaz built a really nice version, compared it to a Keithley DMM 6500, and posted it here.  In the comments below that post, there is an interesting application involving reading the RDS value of a MOSFET.  I've since designed a version with auto-ranging and even ordered PCBs but have yet to populate and test it.

    Frank

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