Attach P lead to GRT EIS with coax?

dwilson · #1 03-24-2013, 10:33 PM

I am trying to figure out the correct way to attach the P-lead to my GRT EIS so that I don't induce a lot of RF noise into my audio system.

It seems to me that if I attach the Tach input from my EIS directly to the P-lead at my mac switch on the instrument panel that I would be transmitting a ton of hash through the wire from the switch to the EIS.

What is the right way to do it?

Thanks

Capflyer · #2 03-25-2013, 04:03 AM

Your EIS most likely came with two 27K Ohm resistors covered in shrink wrap with terminals on each end. These are the resistors to use between the mag P lead and your tach input. See 7.6.1 in the EIS manual, rev K.

rzbill · #3 03-25-2013, 04:28 AM

Use the resistors Mike notes above. Coax is not necessary. I have this system on my mags (no coax on EIS leads) and it is dead quiet.

tc1234c · #4 03-25-2013, 04:29 AM

Duane,

I used a shielded wire. It worked out just fine.
I trust that you are getting close to finish. Looking forward to seeing your first flight.

Ted

dwilson · #5 03-25-2013, 08:16 AM

Thanks everyone. I will install it without coax and use the resistors.

Thanks for the words of encouragement Ted. I am looking forward to first flight in May or June. It is really getting exciting now!!!

Sid Lambert · #6 03-25-2013, 08:47 AM

I think the resistors also prevent grounding of your mags in case the EIS went haywire.

walkman · #7 03-26-2013, 09:54 AM

I installed the resistor close to the EIS end of the wire rather than at the switch end. Should the resistor be at the other end or does it matter?

Norman CYYJ · #8 03-26-2013, 01:41 PM

It makes no difference. Just be sure that where ever you install them that they are mounted securely and that vibration will not cause the wire to and from the resistor to fatigue and break.

rzbill · #9 03-26-2013, 05:00 PM

Well......
It could make a difference if the sense wire chafes and shorts to ground between the mag switch and the resistor. It will kill the mag. If the resistor is close to the mag switch then if the wire shorts to ground after the resistor, the mag keeps running.

Sid Lambert · #10 03-26-2013, 06:44 PM

Mine hooks to the mag switch so I added no risk that wasn't already there. I used those nifty double spade connectors so it's not even in the same crimp.