Which is Better

[Dick B in KY]

A general question - Which is better or gives the most useful information on current electrical system status, in your opinion, a volt meter or an amp meter guage?

Dick B

[chefwarthog]

The two meter are telling you differents things volts meter give your chargeing status at 14.2v the alternator is chargeing ok. if engine is off and landing light is on and the meter reading +-12v battery is ok, if reading is 10.2v one cell is ground.

amp meter will tell you how much amp you consume you don't want to consume more then 80% that the alternator can give you.

[Dave S]

Dick,

In a perfect world - more information is better unless it distracts us from our main tasks.....Both is probably better than one or the other.

However - a volt meter gives more information.

An amp meter basically tells you if current is flowing to the battery (charging it) or from the battery (discharging it).

A volt meter tells you more about what is going on with your electrical system.

For a volt meter -assuming a 12 volt system - Without the engine running - it will tell you if the system is holding at a healthy 12 volts or something less which could be an indication of battery or wiring issues. With the engine running - it will tell you if you have normal system operation at 14 - 14.5 volts (which also would mean it is charging) - or under which indicates the alternator may not be putting out to meet the demand (possibly discharging the battery) ; or, over which can indicate a bad regulator and over charge/overvoltage condition which can hurt a lot of stuff. An ampmeter will tell you if the system is charging but it will not tell you if the voltage is being regulated correctly and may not distinguish between a normal system operation and a damaging over voltage because both will read as a "charge".

For the record - I have a voltmeter - I would have been OK having an amp meter also so I had both - but panel acerage has its limits.

Sincerely,

Dave

[cainbird]

Chefwarthog,
No need to apolagize for your English. I can assure you that your English is way better than my French!

Cain B

[Squirrelfox]

As Eric Stated; they tell you different things. Let me expand a little:

The volt meter is less intrusive as no shunt is needed. It is a simple yet effective method for determining the basic health of your electrical system. However, (my educated opinion) experimentals should use an ammeter with a shunt calibrated at 150-200% Full Scale full load if at all possible. An ammeter coupled with a voltmeter substancially helps to troubleshoot in the air or ground. If you use fuel injection, boost pumps, etc. this becomes all the more important. The ammeter helps you spot trends in failure modes. It can also help quickly identify whether you left that pitot heater on by acccident. Identifying the load for each piece of equipment helps you determine a load shed regime if that alternator ceases to push electrons.

I am biased as I am an instrumentation/avionics type...so I couldn't even imagine not having both on one I build...hope this helps. Remember that voltmeter tells you the force of the push, the ammeter how much is getting pushed.

[HighWing]

Westach makes a neat little dual amp/volt meter that fits into a 2-1/4" panel hole. I had it in my first Model IV and it is going into my new Model IV. The shunt is included in the package. Speaking of shunts, I am helping with a Series V project and just installed the shunt supplied by Dynon. That puppy looks like it could handle the current loads of my whole house - a few calculations and reference to a table shows, it is approximately equevalent to a #6 wire. I am curious as to why the gargantuan size.