Skyview Classic - Two different voltages !!!

[wrb1307reno]

Hi guys, I have a Virus SW with Rotax 912S engine and I have installed two "Skyview Classic", my question is:

On the main flight screen, I have the indication of 14.7 v, but when I enter the menu "Display Hardware Information", I have 13.5 v, both readings at 5,000 rpm. I measured the voltage on the battery with the same 5,000 rpm and I had 14.7 v too.

Why this difference between the two voltages readings?

Thank you, Wolney Rocha ...

 

[sunfish]

Simple answer. You have two alternators and remember that the two buses in the system are electricity isolated except during starting or emergency operation. The “A” alternator is powering the ECU and fuel pumps and the Skyview is reporting Lanes 1 and 2 as 14.7 volts on the CAN bus as it should. The “B” alternator is charging the battery and running Skyview and the rest of the plane systems. It’s showing 13.5 volts as it should. It will vary with the state of your battery charge. It picks up the battery voltage from a connection to the EMS unit and the amperage from the shunt also connected to the EMS.

My installation does exactly the same. Nothing to worry about.

 

[wrb1307reno]

Simple answer. You have two alternators and remember that the two buses in the system are electricity isolated except during starting or emergency operation. The “A” alternator is powering the ECU and fuel pumps and the Skyview is reporting Lanes 1 and 2 as 14.7 volts on the CAN bus as it should. The “B” alternator is charging the battery and running Skyview and the rest of the plane systems. It’s showing 13.5 volts as it should. It will vary with the state of your battery charge. It picks up the battery voltage from a connection to the EMS unit and the amperage from the shunt also connected to the EMS.

My installation does exactly the same. Nothing to worry about.

Hi Sunfish, thanks for your answer but I don't have two alternators, my engine is a Rotax 912S and I have only one power source.

 

[sunfish]

I mean’t 912 iS which has two built in alternators. What is a 912S?

 

[sunfish]

Wolne, section 21-8 of the installation manual I think states the voltage is the “display input voltage “. Maybe that means you are losing 1.2V in the wiring? It might be some internal system voltage, I don’t know.

 

[wrb1307reno]

I mean’t 912 iS which has two built in alternators. What is a 912S?

912 ULS ...

 

[wrb1307reno]

Wolne, section 21-8 of the installation manual I think states the voltage is the “display input voltage “. Maybe that means you are losing 1.2V in the wiring? It might be some internal system voltage, I don’t know.

I don't believe that there are any losses in the supply, the wiring is very short and with the recommended gauge.

 

[swatson999]

I don't believe that there are any losses in the supply, the wiring is very short and with the recommended gauge.

There are always losses. Every wire, every connection, every circuit. The only question is how much. Check for dirty/corroded or inadequate connectors, switches, etc. I'm no EE, but as I understand it, some switches can lead to pretty large voltage drops.

 

[wrb1307reno]

There are always losses. Every wire, every connection, every circuit. The only question is how much. Check for dirty/corroded or inadequate connectors, switches, etc. I'm no EE, but as I understand it, some switches can lead to pretty large voltage drops.

Swatson999, thanks for your reply, I will review it carefully.