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Khamles · 15-08-2008, 16:38

Looking for an answer or even just a re-direct if this has been answered.
I'm interested in getting a good digital multimeter for my boat and don't have a lot of money to do it. I've seen some extremely expensive ones (for me that's over 100 dollars and i've seen up and over 400) and a whole bunch of cheaper ones that range from 20-50 dollars. What do I really need in the way of a multimeter(very basic 12v deep cycle battery for my sailboat)? I know very little about electronics, but would like to attempt to re-wire over the winter and have a good multimeter for checking the battery. Do i really need to go big as far as money, or are some of the lower cost ones more than sufficient for my needs? Any recommendations as to specific models you like?
Thanks,
mike

**David M** · 15-08-2008, 16:50

I would normally recommend a Fluke brand multimeter since they are very accurate and very reliable. I have one at work and one at home and I have always liked FLuke meters. They are also the most expensive. The lowest price I could find for one was $120. Fluke 114 Multimeter Since you want to keep the price under $100, I would go with a digital multimeter from Radio Shack. The price differences you pay are for name brand, reliability, accuracy and features

All you will probably ever need is AC/DC voltage, resistance/continuity and current under 10 amps.

RadioShack.com - Cables, Parts & Connectors: Test & measuring equipment: Multimeters: 42-Range Digital Multimeter with Electric Field Detection

RadioShack.com - Cables, Parts & Connectors: Test & measuring equipment: Multimeters: 15-Range Digital Multimeter

btrayfors · 15-08-2008, 16:54

Mike,

You don't need to spend a lot of money. Actually, although I own some very expensive multimeters (like the Fluke 189) for my workshop, I've taken to buying cheap Velleman multimeters, calibrating them in the 12VDC range, and carrying them with me. Sometimes, I just give them to clients.

They're usually about $20, but I recently bought one for $15 at The RF Connection in Gaithersburg, MD The RF Connection Home Page

If you don't have a way to calibrate them, you can check them against fresh alkaline batteries. Here are some examples from my measurements with the Fluke 189:

Alkaline AA and AAA batteries: 1.580 volts
Alkaline "C" battery: 1.610 volts
Alkaline 9V flat battery: 9.509 volts

"Calibration" is done by opening the meter and tweaking the little potentiometer -- very carefully -- until it reads the same as the calibration voltage.

Not laboratory quality, but close enough for government work :-)

Bill

Chief Engineer · 15-08-2008, 18:29

Sears makes a good one...I have used it for a few years....you can get attachments for it....it also has a temperature probe on it......About 50-60 bucks

drh1965 · 15-08-2008, 18:56

The Blue Sea Systems Clamp Multi is fantastic. I paid around $150 for it though.

S/V Antares · 16-08-2008, 14:39

For the boat I bought a Sears meter with a nice big clamp for amp readings. Suprisingly accurate for $95. It also reads Frequency which can be useful. A thermister probe is optional .

Cheaper than my Radioshack meter which is in my home shop now,

scotty · 16-08-2008, 18:10

i would recommend going to home depot and getting an ideal dvm. i am a sparky who laughs at all the other sparkys buying 200 dollar dvm's for general use. the ideal ones can be had for 50 bucks and the one i use now is 3 years old and tons of job site abuse

this is not homedepot site but its the meter i use daily
Ideal 360 Series Test-Pro Contractor Multimeter

Minggat · 16-08-2008, 21:52

Check out this one at Sailors Solutions. $15

LED lighting, soundproof, Sailor's Solutions Inc.

I have seen some pretty crappy ones that have a lot of features. This one looks good.

Rodz · 16-08-2008, 22:29

Mike, I would recommend a different approach. You said that you know very little about electronics. The knowledge of electronics is not required for boat rewiring BUT a good knowledge of electricity and electrical installation is a MUST! I would not start from buying a multimeter. When you learn about electricity you will know what type of equipment is necessary. By the way ... using a multimeter for battery checking is not the best idea. You can get very inexpensive and accurate equuipment called hydrometer to check electrolyte density and get more accurate results that reflect the battery conditions. For voltage testing you need a load tester that is available in most automotive stores. However, I suggest that you learn about conditions of using any equipment.
Good luck,
Chris

Tim88 · 17-08-2008, 02:13

I agree with Rodz that a load tester is the best, but you need to know a few things prior to that, and this is normally left to some one in the know.

Here in Aust we have to use sealed batteries (if you need a safety certificate) so a hydrometer is of no use for testing battery levels.

I agree you definitely do not need to buy a Fluke, leave those for the experts. I have a very cheap multimeter on board the yacht, for measuring voltage if required, however I do like to measure amps some times and therefore if you can get a multimeter with amps then I think this is the best option. Not only is this handy for measuring the amps used by equipment (and thereby work out your daily usage) but also good for seeing how much charge your battery is taking on board.

Hope this helps!

Tim

Liberty28 · 17-08-2008, 02:24

My personal experience is that anyone who actually thinks that a digital multimeter is giving them accurate voltage readings to three and four decimal places is badly misinformed. If you're concerned about cost, get a simple analog multimeter (gauge and needle) for $10 and call it good. With all due respect to the others, I own a digital myself but I only use it for the fancy ignition features it has for the car.

An example...

Amazon.com: Pocket-size analog multimeter, YG188: Home Improvement

**GordMay** · 17-08-2008, 04:11

I’ve got a couple of excellent, but expensive Fluke multimeters; but admit I’ve been just as happy with my Sears Craftsman DMMs.
Goto:
Sears.com
And look at: #82139, 82141, 81079, 73755, etc ...

See also:

Application Notes From the Fluke Digital Library @
Fluke test tools, answering your electronic, electrical, predictive maintenance and biomedical needs.

Including:

"Beat the Book"
Testing Electrical Systems with a Digital Multimeter:
http://assets.fluke.com/appnotes/aut...e/beatbook.pdf

btrayfors · 17-08-2008, 07:56

I certainly agree that it's good to know some electrical principles when attempting to troubleshoot electrical problems on boats. However, everyone can't be an expert in everything, and there are some pretty complex systems on boats these days, especially when you take account of all the electronic gear piled aboard.

There are some important misconceptions regarding the usefulness and the use of test equipment aboard, especially when it comes to lead-acid battery chemistry.....itself a complex topic.

Here's my take, for what it's worth.

Hydrometers.

(1) These are only useful with flooded batteries since AGMs and Gels are sealed.

(2) Hydrometers measure the concentration of sulfuric acid in the electrolyte and, by inference, the state-of-charge of the cell being tested.

(3) hydrometer readings are affected by temperature, water added, and other factors, and thus are not gospel.

(4) hydrometer readings may tell you little about the capacity of the battery being tested.

Multimeters.

(1)These are invaluable aboard boats for all kinds of testing. They are virtually imperative for the testing of batteries, since analog meters (those with needles) generally don't read close enough to descriminate finely between states-of-charge. The difference between a fully charged battery and one which is 25% depleted, e.g., is only 0.2 volts!

(2) While an expensive multimeter isn't necessary, one with a known calibration is -- at least, it's very good to have on hand. I've seen even expensive multimeters (notably, a Fluke 337 clamp meter) which was way off in it's DC voltage readings. See: Gallery :: Miscellaneous 2007 :: Multimeter02

(3) Most digital multimeters can only be used to measure small amounts of amperage (usually under 10A loads). Clamp-on ammeters, or multimeter clamp-on accessories can measure higher loads.

Voltage of Batteries and What it Means. It can mean little or a lot, depending on how you measure and how you interpret.

(1) Any voltage reading on a flooded lead-acid battery which has been resting awhile over about 12.8 tells you that there's some charge on it, i.e., something is charging it (solar panel, wind generator, battery charger, etc.). Wanna know if your alternator is putting out? Put a multi-tester on the battery terminals while the engine is running. If you measure about 13V or more, the alternator is putting out something. Wanna know how much? Put a clamp-on ammeter over the lead from the alternator. Don't have one? There are clamp-on ammeter accessories which can be used with just about any digital multimeter.

(2) You can get a good approximation of the battery's state of charge by measuring it's voltage -- at the battery terminals -- after it's been resting overnight with no charge and no load on it.

(3) Similarly, if you take a battery off charge and put a modest load on it for a short time -- enough to bleed off the surface charge -- you can then measure its voltage and get a good idea of it's state of charge. However, if it hasn't been exercised in awhile you may get a false reading....voltage will drop faster than it's state-of-charge would suggest.

(4) Voltage will tell you little or nothing about the battery's capacity. A fully charged battery, reading a normal 12.6-12.7 volts after resting overnight, may have a greatly reduced capacity, and when you put a load on it the voltage may drop precipitously in a short time.

Load Testers. Old technology. Used for many years in auto shops to put a relatively heavy load on the battery and see how the voltage holds up. Crude, but workable.

Digital Battery Analyzers. Good ones are expensive ($600 plus). They work by measuring the internal resistance of batteries, and by computer applying an algorithm which computes remaining capacity in CA, CCA, AH, etc. May be used with batteries in any state of charge. Must be used carefully. Not definitive, but indicative and, in my experience, generally correct.

Bill