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  #1  
Old 03-25-2014, 04:26 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
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Default Location of Magnetometer

I had picked a nice place for my magnetometer on fuse pad just fwd of horiz. stab. I just realized that will leave me 6" from the bolts on the stab. I looked for some locations on the floor of the rear fuselage, but in all locations, I will be 12" from either the seat belt cable or the rudder cable.

I did some experiments with a whiskey compass and it seems the stainless cables create more interference than a few bolts.

Can anyone point me to a good location that seems to work well? The bolts, even close, only deviate the compass 1 or 2 degrees.

Larry
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  #2  
Old 03-25-2014, 04:41 PM
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Kahuna Kahuna is offline
 
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Larry,
My experience has been it really does not matter where you put it. The calibration routines in these EFIS's handle deviations for you anyway. Ive installed probably a dozen of these of all different manufacturers over the years. Find a suitable SERVICEABLE location away from heavy iron and press on.
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  #3  
Old 03-25-2014, 04:47 PM
Bavafa Bavafa is offline
 
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Those cables are not very ferrous, you can try them with a magnet to see.

I have installed mine right behind the baggage compartment, directly above the elevator bell crank and as high as the top skin. They have been calibrated and there is no indication of any effect by the cables, as there is little ferrous material there.
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Old 03-25-2014, 05:21 PM
lr172 lr172 is offline
 
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Thanks for the guidance! I just found a thread where several 6 builders have placed it on the rear shelf with good results. I'll follow that original plan.

Larry
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  #5  
Old 03-25-2014, 06:05 PM
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Sam Buchanan Sam Buchanan is offline
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Quote:
Originally Posted by lr172 View Post
Thanks for the guidance! I just found a thread where several 6 builders have placed it on the rear shelf with good results. I'll follow that original plan.

Larry
Larry, that location will work fine. Just make sure you waterproof the mag--I put mine in a plastic baggie prior to attaching it to the deck with zip ties.
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  #6  
Old 03-25-2014, 06:19 PM
lr172 lr172 is offline
 
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Originally Posted by Sam Buchanan View Post
Larry, that location will work fine. Just make sure you waterproof the mag--I put mine in a plastic baggie prior to attaching it to the deck with zip ties.
Good advice. Thank you!
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  #7  
Old 03-26-2014, 08:39 PM
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Mike Stansbury Mike Stansbury is offline
 
Join Date: Dec 2007
Location: Nashville Tennessee
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Default Grt wind correction issue

I'm struggling with this problem. My wind correction and heading are way way off. I've relocated it from behind the baggage compartment to under the emp fairing. Problem there is the trim cable. Rats! I'm very frustrated with this b/c it worked fine for the first 100 hours. Began to malfunction b/c of the seat belts cables and the sliding canopy when open during run up. Grt sent me a new one but I returned it b/c it wasn't the problem. Grts been great but I am at a loss on what to do. Has anyone had to calibrate the wind correction and I'd so did you do this at multiple heights and airspeed.

Mike
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  #8  
Old 03-27-2014, 03:39 PM
Tony Rome Tony Rome is offline
 
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Default my solution

Here's a pic of my solution to the magnetometer mounting.



Tony
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  #9  
Old 03-27-2014, 11:42 PM
lr172 lr172 is offline
 
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Originally Posted by Mike Stansbury View Post
I'm struggling with this problem. My wind correction and heading are way way off. I've relocated it from behind the baggage compartment to under the emp fairing. Problem there is the trim cable. Rats! I'm very frustrated with this b/c it worked fine for the first 100 hours. Began to malfunction b/c of the seat belts cables and the sliding canopy when open during run up. Grt sent me a new one but I returned it b/c it wasn't the problem. Grts been great but I am at a loss on what to do. Has anyone had to calibrate the wind correction and I'd so did you do this at multiple heights and airspeed.

Mike
Mike,

Seems odd that this worked fine for 100 hours. Doesn't seem like a lot of reasons for it to fail all of a sudden. 1) SS cables recently took on a magnet charge (seems pretty unlikely) 2) magnetometer went bad (you seemed to have eliminated that possibility) 3) Problem with EFIS itself (s/w or h/w) including the cable (bad shielding is most suspect) 4) You've recently done something or had something go bad that is causing interference (likely picked up by the cable or magnetometer circuitry itself).

I would think hard about anything that became different or happened around the time of the failure.

EDIT: I would add the fact that moving it to the emp with no change or improvement makes equip malfunction and non-magnetic interference more likely. If the behavior worsened, improved or otherwise changed, then I would think it is magnetic influence. highly unlikely that the magnetic influence would be identical in those two spots. In my testing, I used a compass and moved cables and bolts near it to measure the influence. Neither bolts nor the seat belt cables would deflect the compass more than one degree until I got closer than 4-5".

Good luck,

Larry

Last edited by lr172 : 03-27-2014 at 11:48 PM.
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  #10  
Old 03-29-2014, 07:21 AM
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Mike Stansbury Mike Stansbury is offline
 
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Larry,

Many many thanks for your thoughts. My original position I was very much the same as Tonys pic. ( nice work on the tray btw) relocated to the emp and the issues are the same. Replaced the mag recorded the settings and the magnetic field was un changed. Meaning the sensor was picking up the same level of interference on each separate magnetometer. So I returned the new one and kept my original. Flight was the same on both as well.

Now for the new. Took a flight this past wed. Had wind correction of 15 deg and speed of 68-80 kts. So something is still very wrong. When I slowed to land the wind went 35deg the other way and to 9 kts at pattern alt.

All that's to give you all an idea so what il seeing. What I'm at a loss for is where to begin trouble shooting.

1. I'll start with the compass.
2. I'll record my settings and check it with a sx model my buddy has. My hs doesn't show the mag interference but the sx does
I've bot had any other changes with my hw to date.

Is there any way to wrap the cables to reduce the mag fields ?
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