Ammeter Advice Needed Please

[acornstu]

Okay i would like to buy an ammeter similar to this one.

it's going to be for monitoring the amps in a vehicle. the car is about to have a high output 220 amp alternator installed in place of the factory alternator as well as several car audio amplifiers and off road lights. assuming that i have done all of my math correctly the setup planned should NEVER draw more than 180 amps. this leaves a little room for upgrades, errors on my end, and saves my batteries i hope.

the thing is i'm unsure how much it will fluctuate so i don't know if a digital gauge is the way to go or if i should use an analog gauge.

any descent ammeter i've found that has the potential to reach 220 amps is a ridiculous $150 or more.

and i do apologize as i'm not sure exactly where to put this thread since i'm not sure if i'm looking for purchasing advise or a schematic even :grin:

 

[Sckoarn]

acornstu,

You can put a high power resistor, with a very low resistance in series with your main power feed. Then you can connect in parallel a cheep analog meter, Ebay for $9+. If you do your math right, based on the meter resistance, you can get a constant output metering for under $50. Though it may not have pritty LED numbers for you to read. The resistor may be the most expensive part.

Sckoarn

 

[chuckey]

As Sckoarn said, the name you are looking for is a "meter shunt". The "standard" electronic meter was a 1mA (.001 Amp) with a resistance of 100 ohms. So when the meter was reading 100% the voltage across it would be .001 X 100 = .1V. Now if you used that meter to measure a current of 50A, then 49.999 Amps would go through the resistor leaving then .001 for the meter. if we call 49.999, 50 then a resistance of .1 / 50 = .002 ohms. This would be a flat bar of resistance material with large bolt holes for the current connectors and smaller ones to feed the meter.
Frank

 

[acornstu]

wow! thank you all very much. i'll miss the digital readout, but honestly it'd just be one more thing distracting me from the road. lol. i'll get this all wrapped up and stuff it in my console with my other guages i'm hooking up. and i thank you folks for saving me the $150. not to mention i can say that i "made" this now.