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Old 11-15-2015, 10:20 AM   #1
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Digital volt + amp meters

Help from the electrically-minded please:

I have twin Yanmar diesels with the factory alternators. I want to install digital amp and volt meters so that I can see what the alternators are doing - especially at start up. Meter and shunt would be mounted in plastic box adjacent to each engine.

Would the meter in the pic and link below be suitable for my purpose?
Rating is 4.5-30v and 0-100 A.

Amazon.com: DROK¬ģ Voltmeter Ammeter Volt Amp Multimeter DC 4.5-30V 100A Voltage Currenr Monitor Ampere Testing Gauge V/A Panel Meter Red/Blue Dual LED with Current Shunt Car Auto Motocycle Battery Power: Home Improvement

T.I.A.
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Old 11-15-2015, 10:50 AM   #2
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Doesn't look like it is designed to read amps coming off an alternator as like most ammeters reads off the negative pole such as that off a battery. Blue Seas makes a shunt shifter for this purpose which costs about 65 bucks. If it is going to mounted by the engine, why not just use a clamp meter for your amperage tests? An extremely useful tool to have on board regardless.
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Old 11-15-2015, 11:26 AM   #3
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Do clamp on DC Amp meters really work? I have always used a shunt.
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Old 11-15-2015, 12:39 PM   #4
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Clamp on DC ammeters work fine for diagnosis and testing. You can buy a cheap Chinese one for less than $75. But the one I bought as a spare has a lousy zero drift. When I turn it on it will read as much as 10 amps until I hit the zero button. That much drift makes me leery about its accuracy. But having used it for several things, both low and high amperage situations, it's accuracy is in the ball park after I zero it out. Most tests don't require absolute accuracy.


An Ancor meter I bought many years ago costs about $175 now, but it only has a few tenths of an amp drift when I turn it on. Fluke is one of the best, but about $300.


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Old 11-15-2015, 01:14 PM   #5
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Correct me if I'm wrong, but looking at the schematic on the Amazon site, this unit is designed to measure the output of an alternator.

I wish it read higher than 100 Amps because it would be exactly what I have been looking for to have a meter at the helm showing volts and amps.

While a clamp-on amp meter would work if I went down into the engine room, I usually have other things to do when I first start up.
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Old 11-15-2015, 01:33 PM   #6
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Quote:
Originally Posted by windmist View Post
Correct me if I'm wrong, but looking at the schematic on the Amazon site, this unit is designed to measure the output of an alternator.

I wish it read higher than 100 Amps because it would be exactly what I have been looking for to have a meter at the helm showing volts and amps.

While a clamp-on amp meter would work if I went down into the engine room, I usually have other things to do when I first start up.
Ron, the Victron or Xantrex battery monitors will give you V and A plus battery charge as a %. My LinkPro will display voltage from both start and house battery banks, the current flowing in/out of the house and the % state of charge (SOC). IMO, the SOC is less than accurate and a Balmar Smartgage would be the perfect compliment to achieve the big picture monitoring needs.
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Old 11-15-2015, 01:46 PM   #7
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Thanks Al, I do have a Magnum SOC that does all that but it is located at the nav station which is below the pilothouse, down a couple flight of stairs, so not very convenient. I would like something cheap at the helm so I can look at it when I start the engine.
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Old 11-15-2015, 02:06 PM   #8
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Ron: If the meter proves to be suitable for this service, Amazon offers them with higher capacity by the same manufacturer.
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Old 11-15-2015, 02:41 PM   #9
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Thanks Mike, I did find a 200 Amp meter. Are you going to get one of these? Seems like it should work for you.
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Old 11-15-2015, 02:52 PM   #10
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Ron: Still waiting on more input from the electrically savvy.


The idea is to have them near the front end of the engines so I can include them in my regular after-startup rounds.
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Old 11-15-2015, 03:21 PM   #11
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I bet this would work, but for how long? This auto/motorcycle unit may not hold up to the tougher environment found in marine service. I'd look at more 'fortified' units with sealed circuit boards intended for marine service. As a minimum, I'd consider sealing the circuit board with a product like CorrosionX.

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Old 11-15-2015, 03:29 PM   #12
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Why not just use a State Of Charge meter designed for the boat and RV world?

That way you'll get amps, and volts, and know the state of your batteries all in one handy meter.

Pick your brand. I like the Xantrex Link Pro, but there are others.

Just a FYI, but it's a heck of allot easier to cut a round hole for an instrument than it it is to cut a square or rectangular hole.
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Old 11-15-2015, 04:28 PM   #13
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Al: It is a concern, That is one of the reasons for mounting the meters in/on sealed plastic boxes.

Kevin: Thanks, but that's more sophiticated than I want to get. I'm a worrier and I want to reassure myself that my alternators are putting out, and how much. Square holes are (relatively) easy if you have a small vertcal mill.

Generally I have had good experiences with a/c meters from the same mfg. The three in the pic show voltage and amps at the shore-power inlets and generator. The genset one only lights up when the genny is running.
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Old 11-15-2015, 05:23 PM   #14
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Why not just get something designed to do what you want to do instead of didling around with something you hope will do.

Blue Sea 1834 Panel mount DC digital multimeter with OLED display. Dual channel readout of Volts, single channel readout of amps

Are your tachs driven off your alternators?
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Old 11-15-2015, 05:38 PM   #15
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No guys, all these you list are set up to measure the draw off the negative battery lead. Read the manuals and the specs! For the OP device "2.Current should be tested in the negative pole"

It is very easily be done, but you have to have the right stuff hooked up right. But why not just hook up the right meter to the battery in the first place? Think about it, and look at how +/- ammeters work, and higher end battery monitor kits

Shoalwaters, your OP says:
Quote:
Meter and shunt would be mounted in plastic box adjacent to each engine.
, now you say by the helm... which is it?

Edit" looking further into the manual, it does look like the Blue Seas M2 is a +/- meter.
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Old 11-15-2015, 07:06 PM   #16
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The Blue Sea meter has lots of bells and whistles and it costs nearly $240.00! All I want is an ammeter and volt meter telling me what my alternator is doing. I am not trying to monitor battery condition. Seems I can probably get that for around $20 per engine plus some time spent in my workshop.


George: I didn't say I want to mount the meters by the helm, someone else did.
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Old 11-15-2015, 07:10 PM   #17
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Not sure why a clamp meter isn't OK. Once the engine is started, the alternator is working or not. If externally regulated adjust, if internal all you have is what you have. Yes you may have to check at cruising
RPMs.

Other than that..... in all my tens of thousands of hours underway....not sure it was an issue unless the belt broke or wasn't working from the very start.
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Old 11-15-2015, 09:10 PM   #18
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The Blue Sea meter has lots of bells and whistles and it costs nearly $240.00! All I want is an ammeter and volt meter telling me what my alternator is doing. I am not trying to monitor battery condition. Seems I can probably get that for around $20 per engine plus some time spent in my workshop.


George: I didn't say I want to mount the meters by the helm, someone else did.
Are your tachs driven off your alternators?

I take it you have no amp or volt meters at all now? And no alternator idiot lights?
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Old 11-15-2015, 09:21 PM   #19
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I find it essential to monitor electrical charges and voltages immediately after startup and include them in my normal engine instrument scan while underway. I've never found the need to monitor those values while in the ER.
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Old 11-16-2015, 12:45 AM   #20
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The meter doesn't know or care whether the shunt is on the negative or positive pole. Whole house meters are usually on the negative pole because that makes it easier to measure everything in the system. For alternator or solar panel output, you can just put the shuntg on the positive side and be done with it. I have an amp meter on the positive feed of my alternator and it provides useful information (Like my voltage regulator is currently toast <g>).
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