How do micro ohmmeters work?

Discussion in 'General Electronics Chat' started by thingmaker3, Mar 25, 2006.

  1. thingmaker3

    Thread Starter Retired Moderator

    May 16, 2005
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    How do micro ohmmeters work?
     
  2. n9352527

    AAC Fanatic!

    Oct 14, 2005
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    Same principle as normal ohm meter. A few necessary differences/enhancements are kelvinated measurement wires, sensitive and high precision input amplifier and high accuracy/resolution indicator/ADC. Some expensive models (notably ones with DSPs) have averaging/repeated measurements with noise cancellation algorithm.
     
  3. Polgi-Wan

    Member

    Sep 26, 2005
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    never seen (or used) one ever.... which applications / circuits are these commonly used?

    which brings me to think why do we have 0 ohm resistors?
     
  4. Papabravo

    Expert

    Feb 24, 2006
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    When circuit boards had only through hole components, wire jumpers were used to make optional connections. A piece of wire is difficult for a pick 'n place machine to handle so the 0 ohm resistor replaces the piece of wire used as a jumper.
     
  5. thingmaker3

    Thread Starter Retired Moderator

    May 16, 2005
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    We occasionally use them at work to test bonding on isolated grounding networks. Micro-ohmmeters, that is - not surface mount resistors. ^_^

    I was toying with the idea of adapting something similar (if more crude) for a hobby project.
     
  6. n9352527

    AAC Fanatic!

    Oct 14, 2005
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    You could use one to measure specific conductor resistivity and because most of these micro ohmmeters also measure voltages down to nV range, they are also invaluable in high precision lab works and semiconductor characterisations. These are the ones that I know and I have no doubt that they are also useful in many other applications.
     
  7. hgmjr

    Moderator

    Jan 28, 2005
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    Greetings thingmaker3,

    Here is a publication by Keithley titiled Low-Level Measurements Handbook. It has some interesting info on micro-ohmmeter measurements. It also describes the technique of four-wire measurment.

    hgmjr
     
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