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6226Re: [loopantennas] New file uploaded to loopantennas

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  • Chris Trask
    Jan 13, 2009
    • 0 Attachment
      >
      > File : /UsefulTestEquipment/555InductanceMeter03.gif
      > Uploaded by : alienrelics <alienrelics@...>
      > Description : Dual 555 timer inductance meter. Preliminary schematic,
      > not tested yet. Critique?
      >

      I recall seeing a similar instrument for testing capacitors that appeared in Popular Electronics or some other magazine about 30-35 years ago. It used the same 555 format where the first one was a clock oscillator and the second was a pulse width modulator. They work fairly well given their simplicity. I made one and used it for years until I obtained a cheap LCR meter.

      They can be a bit more accurate if the zero pot is replaced with a third 555 of the same circuit as the second, where a fixed reference inductor (or inductors) is used. This will cancel out the unavoidable errors from the finite switching time of the 555.



      Chris

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