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Author Topic: Ammeters.... Worth it?  (Read 1550 times)
Midwilshire
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« on: November 04, 2013, 05:22:28 PM »

We're planning on adding analog ammeters to the 12v / 24v / and both 120v hot legs of the house system to monitor momentary current draw.  Doing it more out of curiosity than necessity, since we can get most of the important data from the inverter's remote panel.  And I'm a visual learner, so the needles mean more to me than the digits as I pass by.  For those who have installed ammeters, do you actually find them useful and recommend them?  Or did they turn out to be a waste of money?
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Michael & Gigi
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« Reply #1 on: November 04, 2013, 05:55:39 PM »

I have amp meters on both generator legs & like that. None on the shore power side..

TOM
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« Reply #2 on: November 04, 2013, 06:23:15 PM »

Have ammeters on the shore power at the electrical panel. And on the generator feed. Both gauges are on the monitoring panel in the kitchen. You can see how much is being used, knowing how much is available from shore or from the generator. Not totally necessary, but nice to have.

JC
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JC
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« Reply #3 on: November 04, 2013, 06:56:34 PM »

I assume you have VMs, far more useful and the reason most vehicles now use them instead of AMs.

The problem with AMs is knowing how much actual current to route through them and how much to route through a shunt. Too much and things heat up. Also if an AM post breaks (been there) all power is lost in that circuit. Not really worth the effort in my opinion. I stopped using them years ago.
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« Reply #4 on: November 04, 2013, 07:05:29 PM »

What are VMs and AMs?
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JC
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« Reply #5 on: November 04, 2013, 08:26:36 PM »

What are VMs and AMs?

I would guess volt meter and ammeter.
John
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« Reply #6 on: November 04, 2013, 09:17:58 PM »

I agree with Gus Volt meters are the way to go. We have them on 12V 24V 120 V systems. all right above the driver and can just look up and see what is going on. Ammeters can do weird things if post breaks and wires touch etc.

Dave5Cs
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Brassman
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« Reply #7 on: November 04, 2013, 09:47:43 PM »

I'd have a shunt on the house DC side, you're going to have to have something to sense the current, right? On the AC side use current transformers on your AC feeds. They're little coils around the the wires, and they provide the meter input. Not much can go wrong there, unless you put in a switch on the sense wires.
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bevans6
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« Reply #8 on: November 05, 2013, 03:28:40 AM »

Ammeters and voltmeters measure two fundamentally different things and aren't really substitutes for each other.  An ammeter measures usage while a voltmeter measures supply.  Both are very useful, and if you know both you know your power consumption.  There are two broad types of ammeter - one type clamps on to one wire and uses a coil or a Hall effect transducer (measures AC and DC) to measure the current, the other type uses a very low ohm resistor in series with the load and measures the voltage drop across the resistor to calculate the current.  It's called a shunt resistor because it shunts, or bypasses, the current away from the meter, but all of current to the load passes through the resistor so you need to have a resistor that is rated for the amount of current you anticipate flowing to the load.

Voltmeters are most useful in campsites that may have a poor supply service, low or high AC supply can damage equipment so you want to be able to detect that.  Ammeters (I have no idea why they spell it like that but they do) are useful for balancing loads on both sides of a distribution panel or generator that supplies two 120 volt legs, or for load shedding if you are blowing breakers.  While I carry a voltmeter I haven't used it to measure a supply in a campsite yet, I probably should.  I don't have a built-in voltmeter.  I know what the current consumption of all the stuff in my bus is so I haven't found a need for an ammeter.  I do have one of those test plugs that tells me if ground, neutral and hot are present and correct.

Brian
« Last Edit: November 05, 2013, 03:43:42 AM by bevans6 » Logged

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« Reply #9 on: November 05, 2013, 05:28:40 AM »

  Ammeters and voltmeters measure two fundamentally different things and aren't really substitutes for each other.  An ammeter measures usage while a voltmeter measures supply.  Both are very useful, and if you know both you know your power consumption.  ...
Voltmeters are most useful in campsites that may have a poor supply service,  ...

    I have a little meter called a "Kill - a - Watt".  It's about the size of a pack of cigarettes.  You plug it into the wall socket and then plug your electrical device into it.  I don't know if it reads amps directly - I toggle mine between V (I'm amazed at how a normal house plug varies) and watts.  I've measured my entire bus on a 15A 120V plugin, and I've used it for measuring individual appliances.  Also, it will show you how much "parasitic" draw appliances (microwaves, TV's, stereo systems, etc.) use all the time even if they're not "on"; it also shows wattage being pulled by plug in battery chargers etc.  It's pretty light-duty so I wouldn't try to measure more than about 1500 watts but it sure works well for what it does. 
    I also use the "Mate" control box readout for my Outback system to check on voltages (it's particularly good for house battery voltage which the Kill - a - Watt" won't measure).  IMO, we need different types of checks for different systems and conditions, but the inverter readout and a "Kill - a - Watt" are a pretty good combo.   (And I need one of the little devices that shows you if the supply socket is wired right, has a a good ground, neutral, etc. - I'll get one in the next couple of days.)
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Bruce H; Wallace (near Wilmington) NC
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« Reply #10 on: November 05, 2013, 05:50:25 AM »

   For those that don't have a voltmeter, You can purchase units with a plug on them that are useful in the coach or at the pedestal. Good for just checking or leave it plugged in to a receptacle in coach.
Here are some examples; also Camping world used to carry something similar.
http://www.ebay.com/sch/i.html?_odkw=AC+VOLT+METER&_osacat=0&_trksid=p2045573.m570.l1313.TR8.TRC1.A0.X+plug+in+AC+VOLT+METER&_nkw=+plug+in+AC+VOLT+METER&_sacat=0&_from=R40

« Last Edit: November 05, 2013, 05:58:07 AM by chessie4905 » Logged

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« Reply #11 on: November 05, 2013, 07:25:27 AM »


  Hi;
     Some years ago I installed an amp meter on the dash of our
     MC-7.  When I turn on the master and the meter does not
     hit 24v, then I know the bus will not start.  I also know right
     away what the problem is.   I found the meter most valuable.

                                      Merle.
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Oonrahnjay
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« Reply #12 on: November 05, 2013, 08:02:06 AM »

    Hi;       Some years ago I installed an amp meter on the dash of our MC-7.  When I turn on the master and the meter does not hit 24v, then I know the bus will not start.  I also know right away what the problem is.   I found the meter most valuable.        Merle. 

      Yeah, Merle, I have a 12V gauge and a 24v gauge on the instrument panel (for house system and start system) and they're very useful but I think that the above discussion is about 120V amps from shore cords or inverters in the 120V side of the house system.
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Bruce H; Wallace (near Wilmington) NC
1976 Daimler (British) Double-Decker Bus; 34' long
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« Reply #13 on: November 05, 2013, 08:12:52 AM »

How does your amp meter read volts?  I do have a voltmeter on my dash, it is very good to have to know what the charging system is doing.

Brian
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Geoff
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« Reply #14 on: November 05, 2013, 04:38:40 PM »

Not worth it.  Ammeters are a PIA to install and you can figure out what is going on with a simple voltmeter gauge(s).  Dash gauges for DC volts and digital readings from the inverter is all you need.

--Geoff
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Geoff
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