Volt/Amp Pickups Rotax

[jnmeade]

Is there a description of how Dynon measures volts and amps on the Rotax 912ULS?
I'm trying to understand what information is displayed, where it's gotten, how it's processed, etc.
EMS D120

 

[dynonsupport]

Volts are simply the system voltage as sensed by the unit's power input. See this thread for a detailed discussion on that point.

Amps is sensed by a small voltage that is generated by an amps shunt, is a big hunk of metal that is designed to generate a 1 mV of voltage differential between two wires for each amp that passes through it.

 

[jnmeade]

When I get a big amps range swing quite rapidly, does that imply I have a grounding or other connection issue? If so, any place to start working on it, or just "all over"?

 

[Fgerr]

Dynon,
Regarding the "big hunk of metal" used for measuring amps, I assume it is a hunk with a very well known resistance in series with the output of the voltage regulator (and that the D120 is programmed to use the formula: voltage drop = amps through the conductor x resistance of the conductor)?

Where is the big hunk of metal on the plane? What/where are the two wires from the D120 that measure the voltage drop across the hunk?
Thanks.
Fred Gerr

 

[dynonsupport]

When I get a big amps range swing quite rapidly, does that imply I have a grounding or other connection issue?  If so, any place to start working on it, or just "all over"?

First thing to check is that the fuses or fusible links inline with the sense wires are intact.

 

[dynonsupport]

Dynon,
Regarding the "big hunk of metal" used for measuring amps, I assume it is a hunk with a very well known resistance in series with the output of the voltage regulator (and that the D120 is programmed to use the formula: voltage drop = amps through the conductor x resistance of the conductor)? 

Where is the big hunk of metal on the plane?  What/where are the two wires from the D120 that measure the voltage drop across the hunk?
Thanks.
Fred Gerr

Fred:
"Big hunk of metal" is called an "AMPS Shunt" and it's located... wherever the installer prefers to install it, electrically in the electrical system (we suggest three options in our installation manuals), and physically it's located somewhere in the aircraft, often on the firewall (on either the engine side or the pax side, depending on the electrical layout of the aircraft.

Functionally, it's actually a little simpler than what you outlined. It has a minimal resistance such that for every 1 Amp that passes through it, the "sense terminals" deliver 1 mV of voltage. 1 mV = 1A of current; 20mV = 20A. Our EMS units simply read the mVs and translate back to Amps.