Denise,I've eliminated the amp meter (heretofore called ammeter) from my engine panel. Which now makes the alternator output cable only about 3ft, and the starter cable about 5ft. I'll eventually put a voltmeter where the ammeter used to be. http://www.sailnet.com/forums/electrical-systems/134754-being-anl.html
Back to ammeters. I understand the need for the heavy cable to get the amp reading, and it's not good especially on old boats.
I was reading about "shunts" for meters like those from blue sea. A shunt is a resistor basically. what are pros and cons about shunts?
I was reading here Ammeter design : Worksheet It's all beyond me though
I've used handheld clamp type ammeters for many years.
Are there ammeters that work on that type sensing that can be panel mounted?
Yes I know I can "live" without an ammeter on the boat
Shunts read voltage drop at the mV level and the meter transposes this to a current reading.
Most shunts for ammeters or battery monitors for marine use are 500A rated X 50mV..
At a 0 mV drop there is 0A flowing
At a 50mV drop there is 500A flowing
The ammeter is simply calibrated for all points between 0mV and 50mV...
There are hall effect devices out there but they generally have narrower accuracy ranges or they get very, very expensive. It can be very hard to find a hall effect "shunt" that can do 0A - 500A and do it accurately. Usually one that does good low resolution will not do well with high amperage resolution etc...
There is nothing wrong with an ammeter and proper shunt but an ammeter with an internal shunt is a poor choice because these shunts are often barely rated for the gauge panel raring of say 0-50A or 0-30A.....
The best value in an ammeter is the Victron BMV-600 which tells you quite a bit more than just amperage.....