Dynon ammeter readings

[uk_figs]

I have the dynon ammeter shunt installed in position A from the D120 installation guide and with the engine running the indicator is in the green but the numerical readout shows -10, the battery voltage is around 14.2 which I believe shows that the alternator is working OK (plane power 60A). In reading the various threads I have now confused myself as it would appear that with the alternator supporting the aircraft loads and a charged battery I should be showing zero amps. Can someone provide a quick primer on what I should expect to see on the ammeter, full aircraft loads are calculated to be around 20A.
Thanks

[Brantel]

I suspect that if you run the engine for some time, you will see that number move closer to zero once the battery gets its top charge back from starting the engine.

If you want it to read + amps when charging the battery, just reverse the shunt leads.

[uk_figs]

Brian
Thanks, I will check that today

[frankh]

Where position A is..but if that is in the ammeter B lead then it is either flowing 20 TO the alternator (from the battery)...no way that is happening...Or you have the leads swapped on the ammeter shut.

If you have 14V+ with the engine running and some load switched on (lights, radios etc) then the alternator is working perfectly.

Frank

[Brantel]

"A" is in and out of the battery

[dynonsupport]

Position A puts it between the alternator lead and the battery. It should measure only battery current.

Generally this means you should read a negative number if the alternator is not generating enough to power the aircraft, and positive when the alternator is generating excess power and charging the battery.

First thing is that on a Rotax, the alternator probably doesn't have enough juice at idle to power your whole system. So it's quite possible that on the ground at idle, you'll read a negative number.

Once rev'd up, you'd expect to see positive numbers for a little while until the battery charges. These can be quite large in the beginning but should trail off quickly if all you are recovering is the energy lost from a start. If your battery was low, it can take a long time.

If you are seeing the reverse positive/negative from this, just swap the two sense leads on the shunt.

[uk_figs]

Checked today and I appear to have the shunt wires reversed, switching on a load with engine not running shows +ve and with engine running load is -ve. As Brian said after about 20 minutes in the air the ammeter was reading zero showing that the battery was charged.
Guess the cowling comes off yet again