Ammeter

[Bosunof]

I have a batch of three batteries, 2 for domestic and the third for engine starting. What is the outline circuit diagram for putting the ammeter in the circuit so that I can measure demand/supply from the two sets when in use? It is a + - ammeter.

As you might guess, I am no electrician but I do need to see what the demand is when away from base.

 

[1955patric]

Depends on whether it is shunt driven ammeter or a series one. If it is series then in series with the circuit you want to measure from. If shunt driven, the shunt is normally connected in series with the battery negative. What sort of currents are you going to be measuring - reason I ask is that a series connected one will need cable capable of carrying the full expected load plus a factor of safety.

 

[Bosunof]

Thanks for responding Patric. How would I see whether it is shunt or serial? Can I rig it so that it can read the current of the batteries I am using? Its a pity you are so far away to come and see, but there you are and here I am.
Cheers
Frank

 

[Billjratt]

A shunt meter in the common neg line is good to measure everything.
The series/in-line meter is not efficient and will limit current.
A sensitive centre-zero meter will measure the drop across the main battery lead, thus obviating the use of an expensive shunt (and extra connections).
All you have to do is move the negative feeds to the domestics and chargers from the battery post to the engine connection

 

[VicS]

A couple of links you may find useful. Some of the basics and the sections on instruments in the "Boat electrical notes" on This website

Also perhaps the "12 volts handbook" from HERE

 

[VicS]

Cant stop now but here is a diagram I did for another forumite recently.

Shows an ammeter to monitor use and charging of the domestic bank and also a couple of voltmeters ( one for the domestic bank and one for the starter battery).

Shows both options for an ammeter, either local to the battery without a shut or remotely with a shunt.

Be back later to answer any questions arising.

 

[1955patric]

Sorry for the delay getting back to you. A shunt meter requires a seperate shunt ( looks like two heavy brass blocks connected by a series of thin strips. It will have 2 heavy duty posts to take the battery cable and two smaller tappings for the signal cable which supplies the meter. Series ammeter will have 2 heavy duty posts on the back.

 

[Bosunof]

Thank you all. That has given me something to fill my Thursday at the marina.

 

[William_H]

I would have said that a +- ammeter as you describe it was the type used on old cars. It will perhaps show + or - 20 amps on a tiny scale with just a few graduations. This type is usually a moving iron meter and requires all the current being measured to flow through the meter.

Perhaps more recently we occasionally see a moving coil meter with more graduations which is in fact a very sensitive meter. This type if graduated in lots of amps will probably have the shunt inside the meter case so all current must flow through the meter case.(you can sometimes remove the shunt from the case to a more convenient location.) However if is graduated in microamps or just no graduations (eg a tuning meter from an FM radio) then this kind will need an external shunt.

The external shunt has the convenience of not needing heavy wires to go to the meter. It also means you can have several shunts for different circuits and just switch the low power meter to the different shunts.

Switching of the high current wires to the meter is fraught with problems

A photo of the meter might help identify which type it is.

In the end you probably only want current measured for the domestic batteries both in parallel so only one shunt needed.

good luck olewill