DC ammeter

[thaeni]

Need to know how to wire up an ammeter. I got one to track how
many amps I'm using at any given time. I wired it up to my house
battery (positive to positive negative to negative) and all I got was
allot of sparks like it was shorting out. What am I doing wrong?
Thanks

 

[Rick]

Well without seeing what type it is.... The way they work basically. You must supply the meter 12 volts positive for it to work normally from the DC panel (if that is where you intend to mount it). The meter gets its amp reading through the negative terminal and that signal is supplied by a shunt. Again to keep it simple you must find your negative battery bus (perhaps behind your DC panel depending on the boat). The shunt will go between the negative battery cable that goes to the bus and where the negative battery cable connects to the bus. Now there should be a lead that connects to the meter from the shunt. Thats how it reads the load.

That is assuming you didnt fry the meter already. Again that is basic. They arent really that hard to hook up. Some of the smart guys here will chime in im sure. I did mine and I am pretty much a cave man!

 

[heart of gold]

Essentially what you did is short your battery as, depending on what type of meter it is it is pretty much a straight through connection. that is where all your sparks came from. If your meter is to be installed without a shunt, it needs to be between your positive battery lead and any loads that you want to read. The positive and negative markings on the meter indicate what direction to install it. Positive will go to the positive battery side while negative will go to the load side(not the negative battery post). Lots of them come with a dash light in them as well so there may be small wires for connecting it. If your meter has an external shunt, then it is installed the same way, then the meter is connected to the shunt leads. You have to be careful about shorting these batteries out as the heat and current generated can cause a battery to literally blow up as the cells will super heat when shorted for even a few seconds.

 

[Maine Sail]

You have to be careful about shorting these batteries out as the heat and current generated can cause a battery to literally blow up as the cells will super heat when shorted for even a few seconds.

You would need some darn serious leads on that ammeter in order to short out the battery. You can melt a 12 Gauge wire in half before a good heavy duty the battery even hiccups.

I blew a 250 amp ANL fuse on my C-310, due to sloppy factory wiring, and the batts were no worse for the wear..

Many of these batteries can deliver upwards of 1000+ cranking amps and the small wires, on a small ammeter, would not even be a contest for the battery. The ammeter though is likely fried.

Most all high current reading ammeters use an external shunt and you'll likely need one if it is to measure any decent current..

 

[heart of gold]

You are right of course Maine Sail, I guess I was thinking of the extreme. Still not a good idea to short them out. Cheers, Ian

 

[Maine Sail]

You are right of course Maine Sail, I guess I was thinking of the extreme. Still not a good idea to short them out. Cheers, Ian

Yes, never a good idea to short anything across a battery..

 

[Dan Johnson]

Thaeni...

to clarify Heart's good explanation, disconnect and reconnect the positive lead coming from the battery to your switch panel to the positive terminal on the meter. Hook the other meter terminal to the connection post that the incoming positive wire was connected to at the panel.

An ammeter is wired in series so all the current runs through it, whereas a voltmeter is wired across the positive and negative as you you tried to do initially.

 

[Bill Roosa]

Positive and negative

as a general rule if you connect the ammeter on the ground side of the circuit you can capture all the parisitic loads that don't go through the "main" switch on the positive side. Starters, alternators, bilge pumps and stereo memory come to mind. If you are not concerned about those (and it does depend on how your system is wired BTW) then either is fine.

 

[Dan Johnson]

Bill R...

what negative (ground) wire would you connect the ammeter through to determine parasitic loads for items not connected to the main breaker panel such as the bilge pump. And, wouldn't you need a whopping big ammeter (or shunt) and wiring if inserted in a battery negative lead to capture the current load of a starter motor when energized?

I get the feeling that Thaeni has a simple ammeter (maybe 0-60 amps max) that he wants to measure loads going through the breaker panel.