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Theory Behind-Using analog opposed to digital meter in some troubleshooting

Theory Behind-Using analog opposed to digital meter in some troubleshooting


Old 09-21-14, 05:42 AM
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Theory Behind-Using analog opposed to digital meter in some troubleshooting

To help me expand my knowledge more of troubleshooting I have noticed that many members here and elsewhere suggest using an analog meter in certain troubleshooting scenarios in favor of a digital meter.

I have always favored the digital only because I have come to rely on it mainly because that is all I have owned and used.

Is it more of preference than necessity to help troubleshoot?

Perhaps some members can share with me and others here (a learning exercise) a few scenarios where using an analog meter would provide more accurate results than a digital meter would.

I have googled this but it gets quite confusing. Maybe an example of a problem circuit followed by an explanation of the technique would be helpful.

Thank you so much.
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Old 09-21-14, 06:19 AM
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It is a mater of impedance. Digitals have a much higher impedance then analog. A digital can show an induced voltage with no real amperage. The much lower impedance of an analog will drain it off. Sometimes it is capacitive voltage. Two insulated wire together form a basic capacitor that can store a charge. The low impedance of the analog meter will drain the charge the higher impedance of the digital doesn't. Some digital meters like high end Flukes have special circuits to detect these problems and give an accurate reading, most don't.

Then too a digital meter relies on a battery to power its circuit. Readings can get strange when that battery is low. An analog multimeter does not depend on a battery. (The battery in an analog multimeter is only for resistance measurements.) Very easy to forget to turn off a digital meter so if it isn't used often it can be near dead the next time it is used.
Old 09-21-14, 06:51 AM
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When fluctuations in voltage are important, like investigating a circuit board, a digital meter doesn't display what is happening, just different numbers not representative of the changes or rate of change. An analog meter will show a jump in the needle, from which experience helps to determine what is happening.

I have both meters and although I prefer the analog, there are times when a digital provides more accurate numbers. Reading one ohm on an analog isn't very accurate.

Ray covered the rest.

Old 09-21-14, 06:57 AM
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I think an analog meter is better suited to dummies like me I've never had any issues using an analog meter but never have been able to master my digital meter I don't know the reason why but they say that digital meters won't work well on a lot of the older cars and tractors.
Old 09-21-14, 07:28 AM
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Phantom voltage is what throws people off in many cases with a digital meter. The meter shows there is voltage present when there really is none. As Ray mentioned, most higher end meters will filter this.

Another time when an analog meter is helpful is with automobile wiring, namely trailer wiring. A digital can not react fast enough to work on a circuit that is flashing. Analog works just fine.

Bottom line, if you have a digital meter, like it, know how to use it, and are aware of its possible limitations, you should be OK. I like to have both in my tool arsenal along with a non-contact tester for a quick test to see if a wire might be hot.
Old 09-21-14, 08:11 AM
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And just for educational purposes this opinion of digitals: http://www.ohio.edu/people/postr/bapix/vtvms.htm

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