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Main Section => Welcome to our virtual Pub Meeting ... => Topic started by: Larry S. on August 29, 2019, 04:27:52 PM

Title: Ammeter Shunt
Post by: Larry S. on August 29, 2019, 04:27:52 PM
Hello everyone -

A year or so ago, when starting to look at installing the new wiring harness, I took an inventory of the electrical components I had.  Inside the box of items was a boxed, NOS C.A.V. 60-0-60 ammeter, part no. 5539/233AB.

I have no clue where it came from; there are no records of it in any of my notes or in any emails and I know it did not come in the box of goodies that came with Grover.

I'm not sure if it will ever be installed, but in case it is - do any of you have a recommendation for a shunt - brand/make/style?  I know you have to match the shunt to the ammeter, yet when I do an online search for a shunt for this thing not much of anything comes up except for "you need to match the shunt to the ammeter".

Thanks!   :tiphat
Title: Re: Ammeter Shunt
Post by: Worf on August 29, 2019, 05:07:48 PM
The shunt is connected externally and usually comes with the ammeter. I cant tell if it is actually there on your one.
See photos here https://www.ebay.ie/itm/VINTAGE-CAV-AMMETER-60amp-lorry-Car-etc-/254341465707?hash=item3b37eec66b (https://www.ebay.ie/itm/VINTAGE-CAV-AMMETER-60amp-lorry-Car-etc-/254341465707?hash=item3b37eec66b) for detail.

AFAIK they were fitted to military vehicles, so you might find one on a scrapper.
Title: Re: Ammeter Shunt
Post by: Larry S. on August 29, 2019, 08:03:38 PM
Quote from: Worf on August 29, 2019, 05:07:48 PM
The shunt is connected externally and usually comes with the ammeter. I cant tell if it is actually there on your one.
See photos here https://www.ebay.ie/itm/VINTAGE-CAV-AMMETER-60amp-lorry-Car-etc-/254341465707?hash=item3b37eec66b (https://www.ebay.ie/itm/VINTAGE-CAV-AMMETER-60amp-lorry-Car-etc-/254341465707?hash=item3b37eec66b) for detail.

AFAIK they were fitted to military vehicles, so you might find one on a scrapper.

Nope, there isn't one attached, just the fittings for it. 

I did run across some military ones while searching, those were listed as 24v IIRC.  Did the military use 12v ones?  Don't know why they wouldn't...

Thanks for the link as well, I was wondering how they attached, just hadn't gotten that far yet.
Title: Re: Ammeter Shunt
Post by: g6anz on August 29, 2019, 08:16:58 PM
have a look here https://www.bluesea.com/support/articles/Metering/552/Sizing_a_Shunt_to_a_DC_Ammeter
You will need to know the FSD of the meter without any shunts, it will be around 1mA or 10mA from that you can calculate the value of the shunt required. The value will be very low in the region of 0.001ohm about the resistance of a piece of thick wire a few inches long.
Title: Re: Ammeter Shunt
Post by: Worf on August 29, 2019, 08:35:53 PM
I THINK that meter has a 5ma FSD, but I also think it is for a 24 volt setup. So if you were using it on a 12v setup  :stars (getting beyond my pay grade!)
Title: Re: Ammeter Shunt
Post by: g6anz on August 29, 2019, 09:44:32 PM
The voltage it works on is irrelevant. Its just monitoring the current be it at 12v 24v or 120v.
Title: Re: Ammeter Shunt
Post by: Larry S. on August 30, 2019, 12:08:17 AM
Quote from: g6anz on August 29, 2019, 08:16:58 PM
have a look here https://www.bluesea.com/support/articles/Metering/552/Sizing_a_Shunt_to_a_DC_Ammeter
You will need to know the FSD of the meter without any shunts, it will be around 1mA or 10mA from that you can calculate the value of the shunt required. The value will be very low in the region of 0.001ohm about the resistance of a piece of thick wire a few inches long.

Yup, found that article last night and read it.  It did help with understanding how it works; now just need to figure out what shunt would be best and where to get one.  Really figured there would be all kinds of recommendations online as to what one to get.