Do You Need To Run Second Ground Wire To Sensors??

[Dynon101]

Believe it or not...some of us really do read instruction manuals...

I was re-reading the SV installation manual for the umteenth time and caught this little recommendation:

"be sure to connect a ground wire between your engine block or avionics ground block and any of the SV-EMS-220/221’s ground pins."

Can you please elaborate on this? I am building a composite airplane so this grounding thing is most important...

My original plan was to ground the EMS to a solid ground and then run one of the black EMS ground wires out to the individual sensors and call it a day...HOWEVER...

It appears by the recommendation in the manual that one (me) should not only utilize the EMS ground wire but we (me) should also run a second wire from the engine and/or avionics ground to each individual sensor IN ADDITION to the EMS provided ground wire.

I would have thought that the EMS ground was sufficient.

THANKS!!!

 

[Raymo]

They key here is that everything is properly grounded together. If not, you may experience odd or intermittent sensor readings (e.g. CHT).

The engine must be grounded to the airframe/battery for the purpose of starting the engine. This should be a fairly large gauge wire similar to the one that runs to the starter. You can attach this to a forest of tabs (FOT) stud on the firewall where sensors can be individually grounded, along with the EMS and battery. The FOT typically goes through the firewall where internal electronics are grounded.

 

[KRviator]

I did not run an "instrument ground" to the engine, only the big ground cable to the firewall. If you have an instrument ground in addition to your normal ground path, you can possibly introduce multiple paths depending on the condition of the two, which might affect readings.

Also - and the main reason I did it - is if the main ground cable loosens and you try to start the engine, the full starter current is going to try to pass through the EMS until it cooks from the overcurrent...

 

[Dynon101]

Dynon Tech Support:

I have a composite airplane. All engine sensors are remote mounted on rubber hoses except the oil temperature sensor.

Can you PLEASE answer this question:

The Installation Manual says: "be sure to connect a ground wire between your engine block or avionics ground block and any of the SV-EMS-220/221’s ground pins."

Do I also need to run a second wire from the engine and/or avionics ground to each individual sensor IN ADDITION to the EMS provided ground wire.

OR

The EMS provided ground wires are the only ground wires needed to be run out to the sensors.

 

[jakej]

FWIW the last sentence is correct. Additionally I add a second ground wire from engine to airframe ground - just to be sure, never have had any ground issues using that method

 

[Dynon101]

thanks Jackj... my airplane is plastic.

 

[jakej]

Does not make ANY difference, mine is 'plastic' too ;D

Glasair IIS-FT