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<blockquote data-quote="n2audio" data-source="post: 1142052" data-attributes="member: 540940">I&#039;ve always been a bit skeptical of people just &quot;whipping out&quot; the trusty DMM for a measurement that&#039;s a fraction of a fraction of an ohm.&nbsp; All the DMM&#039;s I&#039;ve messed with (a few good, a few cheap) detect a short at anything below an ohm or so.Another thing I see some people claim is you should ground somewhere that gives a reading around .3.&nbsp; Which can&#039;t possibly be right.And you mention running a lead (relatively small ga I assume?) to the battery in which case the resistance of the wire would be WAY higher than the resistance of the chassis.&nbsp; So that couldn&#039;t possibly provide an accurate measurement either.The only method I&#039;ve heard to truely measure the resistance of a good chassis ground that makes sense would be to have some sort of power supply that can pass a huge amount of current through the chassis and use a DMM to measure relative voltage drop at various grounding points and use that to calculate resistance.Regardless - I just pick a spot that&#039;s convenient that doesn&#039;t give me any noise issues.&nbsp; In my car it&#039;s a seat belt bolt, and in my wife&#039;s SUV it&#039;s a seat frame-to-floor bolt -- it used to be on a luggage strap bracket bolt in the cargo area, but that gave me alt whine.</blockquote>

[QUOTE="n2audio, post: 1142052, member: 540940"] I've always been a bit skeptical of people just "whipping out" the trusty DMM for a measurement that's a fraction of a fraction of an ohm. All the DMM's I've messed with (a few good, a few cheap) detect a short at anything below an ohm or so. Another thing I see some people claim is you should ground somewhere that gives a reading around .3. Which can't possibly be right. And you mention running a lead (relatively small ga I assume?) to the battery in which case the resistance of the wire would be WAY higher than the resistance of the chassis. So that couldn't possibly provide an accurate measurement either. The only method I've heard to truely measure the resistance of a good chassis ground that makes sense would be to have some sort of power supply that can pass a huge amount of current through the chassis and use a DMM to measure relative voltage drop at various grounding points and use that to calculate resistance. Regardless - I just pick a spot that's convenient that doesn't give me any noise issues. In my car it's a seat belt bolt, and in my wife's SUV it's a seat frame-to-floor bolt -- it used to be on a luggage strap bracket bolt in the cargo area, but that gave me alt whine. [/QUOTE]

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