 RPM Measurement Question |
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| Ansbacher |
 Dec 23 2018, 08:06 PM
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Senior Member  Group: Members Posts: 689 Joined: 4-July 14 From: Tampa Bay, Florida Member No.: 17,589  |
When measuring the RPM of my '74 2.0. with conventional points, using a digital VOM I get twice the expected RPM values. Yes, I have the VOM set to 4-cylinder. I know what a 1,000 RPM idle sounds and feels like, so I am sure it is the VOM reading double. Analog meter says 1,000 yet the VOM says 2,000. What gives?
Ansbacher |
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| jcd914 |
Dec 24 2018, 12:01 AM
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Advanced Member Group: Members Posts: 2,081 Joined: 7-February 08 From: Sacramento, CA Member No.: 8,684 Region Association: Northern California |
So I don't have experience with the DVOM you are using, my DVOM that has RPM uses an inductive pick up that clamps around a spark plug wire.
Digital meters are more sensitive, check that you have good clean connections (especially the ground) and make sure your leads are not laying on or very close the the plug wires or coil wire. The high voltage in the plug/coil wire can create enough of emi that your meter could sense it as a pulse. Jim |
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