Posted by KEB1 on May 19, 2010 at 19:54:57 from (97.124.140.124):
In Reply to: Electrically Weird? posted by GUIDO on May 19, 2010 at 19:15:10:
What you're seeing is an artifact of the way digital multimeters work. A digital meter has very high input impedance (millions of ohms), which means it takes very little current (millionths of an amp) to operate the meter. Even at 60 Hz, the stray capacitance between the table top and the power wiring provides plenty of current.
Small currents can also be induced in loops...try holding the meter leads in your fingers, one in each hand, and see what it reads. You'll be reading the voltage induced in the electrical loop formed by your body and the meter leads from the stray magnetic fields created by the AC power wiring.
Mechanical analog meters require some flow of current through the meter to physically move the needle, and had input impedances measured in thousands of ohms, or even hundreds of ohms for cheapie meters. With a relatively low imput impedance, stray capacitance can't pass enough curent to operate the meter, and you don't get these kinds of stray readings.
Hope this helps a little....kind of hard to explain without getting into a lot of engineering terminology, but there's nothing at all surprising about what you're seeing. A lot of time has been wasted in electronics labs getting erroneous readings because the engineers and techs don't understand this phenomenon.
We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]
Today's Featured Article - Grain Threshing in the Early 40's - by Jerry D. Coleman. How many of you can sit there and say that you have plowed with a mule? Well I would say not many, but maybe a few. This story is about the day my Grandfather Brown (true name) decided along with my parents to purchase a new Ford tractor. It wasn't really new except to us. The year was about 1967 and my father found a good used Ford 601 tractor to use on the farm instead of "Bob", our old mule. Now my grandfather had had this mule since the mid 40's and he was getting some age on him. S
... [Read Article]
Latest Ad:
1964 I-H 140 tractor with cultivators and sidedresser. Starts and runs good. Asking 2650. CALL RON AT 502-319-1952
[More Ads]
All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy
TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.
