PPL Aircraft General Knowledge: Centre-Zero Ammeter
 

Hi all,

A quick question.. in a circuit where the battery is grounded, fully charged and is connected to a switch, centre-zero ammeter, busbar and alternator, does the centre-zero ammeter display 0 (needle in the middle) because the battery is fully charged, or will the needle be slightly on the positive side to indicate current flow from the alternator to the battery, even though the battery is fully charged and the busbar's load is supplied by the alternator.....

I'd go for the latter (0) but not 100% on this.

Thanks in advance,

PJ

zero or slight positive are both normal. Slight positive is probably the prefreed answer in an exam. See also Loadmeter which is fitted in some aircraft instead which can be confusing.

https://books.google.co.uk/books?id=...charge&f=false

Turns out the correct answer was 'slightly on the positive side'... and I have yet to find evidence to suggest that is technically correct... but hey ho. The question explicitly said 'battery is fully charged' which means the ammeter should (and on a new aircraft, does?) display 0.

The needle on the right simply means that the generator is pumping out more than the battery does the other way - as mentioned, this is normal