How accurate of an multimeter do I need?

[deleted-326417]

Hey folks of ScienceBuddies.com! I need some help with my science fair project. Under the procedure section of Power Move: Manipulating Magnets to Improve Generator Output, it states that multimeters that support measurements of alternating current or alternating voltage accurate enough to be used in this electronics science project are expensive. Well, how accurate exactly do they need to be? I want to do a good science experiment, and for this one, it seems like a multimeter might just be an investment worth making. Does anyone here know the answer to my question? I appreciate any help at all.
Yours truly,
ElevatorandEngineeringGeek

[deleted-249560]

If you plan on doing more projects using electricity, a good multimeter will prove itself invaluable over time. The difference between a good one and a poor one is more than just ranges and functions (although those are important) but longevity and accuracy. You can buy some surprisingly cheap full featured meters at the freight discounters for $25 but those are notoriously inaccurate and unreliable. Centech is a common brand name for those and I like to keep one in my car (if it breaks I won't be sad). One I've had for less than a year thinks a fully charged 12V car battery is 18 volts. You want a meter that gives you an accurate measurement and stays consistent. Meters like that can be found for under $50 if you watch for deals. Radio Shack's meters are not bad. You can also look on the web for meters from Extech, Fluke and BK Precision and be happy with just about any of those. Fluke is a brand often preferred by professional electricians and engineers - for good reason.

For most of the projects here you can get by with a junky meter since the effects you're measuring tend to be relative to each other and not absolute numbers. You'll be a lot happier with a good meter if you can manage it.

Howard