Become a Multi-Meter Master!
A lot of boater's keep a multi-meter on board. These units, which are also referred to as a DVOM (digital volt/ohm meter) are the key to troubleshooting electrical system gremlins, provided you know what to look for and how to read the meter. Most boaters fall short on that last requirement. So with that thought in mind, I'm going to devote a few blog entries into showing you how to use the multi-meter and understand what exactly it's telling you. The diagrams I'll use for this are excerpted from my book The Powerboater's Guide to Electrical Systems. The sailors in the crowd should not be intimidated by that title, because electricity really doesn't know whether its on a powerboat or a sailboat, all of the same techniques apply.
Selecting a useful meter
There are literally hundreds of meters available, but not all of them have the functionality you will need. The $9.95 analog meter available through Radio Shack will tell you a few things, but is far from the best choice if you really want to figure out what's going on with your electrical system. The best choice right now will include the ability to measure amperage, both AC and DC, volts AC and DC, ohms of resistance and electrical continuity. Go digital. Analog meters are going the way of pay telephones, they work, but are harder to use and not as convenient as they used to be. My current favorite is distrubuted by Blue Sea Systems and is available online for about $175.00. Look for model 8110. West Marine also sells this unit. This unit offers the best ranges of measurement for both amps and volts for most all marine applications. The mini-clamp type meter is shown here:
You can check out the specifications for this meter at: http://bluesea.com This site is one of my absolute favorite references for all things marine electrically related.
Tomorrow, I'll begin showing you how to use this meter, or just about any meter you select.