GRT Magnetometer issues

Folks,

I have a remote magnetometer that I can't seem to get working correctly. It supports my recently installed Mini-AP...which replaced a NSD1000.
My initial install was in the same location as the recently removed NSD1000 remote compass - I modified the bracket and put it in the same place.
This resulted in about 15-20 degrees of variation from my SIRS compass and the other (AFS) EFIS unit.
Performed the calibration according to the documentation provided
No improvement...
Updated software per the website
Re-ran calibration
No improvement...
Sent the magnetometer in for factory alignment
No improvement...
Removed unit from the NSD mount and velcro'ed it to the fuselage floor to manually adjust the alignment (about twenty degrees off) to get the numbers to align on the ground
Flew in that configuration - no consistency in display.

Mark subsequently recommended installing it in the wing so I made up an extension cable for the 4 pin RS-232 cable and taped it to the wing - not I did not fly this way - simply towed it around in a circle!
This resulted in a 34 degree variance from other indicators.

Anyone out there have a known good environment with a four pin serial GRT magnetometer that would be willing to swap mine in and test?
If it works in someone else's plane, then I know I need to fix my installation area.

FWIW, I installed mine behind the rear buckhead where my Dynon remote compass was located and working flawlessly. I could not get the GRT to calibrate, until I moved it onto the left wing tip.

Is yours a four-wire DB9 connector little black box?
If so, how difficult is it to get to?

I taped mine to the wing (did not fly it that way - simply towed it around my grass field) and it was 34 degrees off - even after factory calibration. I think it is defective - but can't prove it - unless I can install it in a known good environment and show it not working.

Thoughts?!

recapen said:

Is yours a four-wire DB9 connector little black box?
If so, how difficult is it to get to?

I taped mine to the wing (did not fly it that way - simply towed it around my grass field) and it was 34 degrees off - even after factory calibration. I think it is defective - but can't prove it - unless I can install it in a known good environment and show it not working.

Thoughts?!

Click to expand...

Yes, mine was the little black box, 9 pin with nylon bolts.
Mine is attached to the last outboard rib inside the wing tip

Similar problem

When I purchased my RV7A two years ago I experienced a similar problem. Like you I had to move my magnetometer to the wing tip. I was told by GRT to check my counter readings to see if anything might be giving out electromagnetic interference. Do this by turning everything off and then turn things on one at a time while watching your counter readings. Also transmit on your radio and what the readings.

If anything causes a rapid change to the counter readings then you've discovered your problem electromagnetic interference. Did you use shielded wire? That is a long distance to use unshielded wire because GRT magnetometers, in my opinion, are very sensitive to electromagnetic interference. Common things that can cause interference are the radio, strobes, aircraft lights. Sometimes ferrite filters can be helpful.

Good luck and keep talking to GRT. They can help you identify the problem.

Yup, shielded.
For this test, it was taped to the wing. It was off by 34 degrees - with almost nothing running - I didn't even get to the point of turning other stuff on!

GRT has suggested that I re-run the Set Final Magnetometer and Instrument Orientation procedure as outlined on paragraph 4.6 of the X manual revision A6. I'll do that this weekend but based on the severity of my differences, I'm not putting any money on the outcome.

After that, I may be asking someone to take my unit and put it in their environment (wing) to test......

You might try it back where you had it and run the test on the ramp with the engine and everything running and the canopy closed. You will have to hold your brake down for the turn. Worked for me, found out with my slider canopy open it was 8 degrees off. If it works maybe something in your panel needs to be on.

Already did that - with the engine and entire system up and running...for the fine calibration procedure as specified in the manual. Was off when I started, rebooted, and finished.

I am starting to question the validity of the equipment. Wish I had a hangar neighbor with a working system to throw mine in to!

It has been back to the factory for their calibration and out on the wing - with significant errors all around!

GRT is now saying that I have to re-do the position and calibration tests - which would negate the calibration I got from the factory when I sent it in.

Not a happy camper with this right now!

Ralph,
My 2010-era magnetometer, coupled to a GRT HX, is behind the baggage area in my -10, and has always worked perfectly. I am starting my annual next week, so I'll have easy access. If you think this is the same magnetometer as yours, and you want to mail yours to/from CA, I'd be happy to substitute it for mine and taxi in a few circles. But first, is there anyone local who can look? Sometimes fresh eyes see something you overlook. Are you sure you have the connections correct, at both ends? (I've seen people push the pins into the wrong hole in the connector. Those numbers are tiny!). Did you check the wires with an ohmmeter? Is it mounted upside down? (I've seen this!). Did you use non-magnetic hardware to fasten it down? Did you put a compass in the area and see anything odd? etc.
Bob

Bob,

Mine replaced a NSD1000 magnetometer - in the same place.
Same bracket, same SS screws. Then velcro'ed to the floor behind the baggage wall. Rang out the wires as well.

Now GRT tells me to put it in the wing and re-do the position and calibration...after I taped it to the wing and the results were not good! Next tape it back to the wing and re-run the position and calibration.

Looking for someone closer to N06 than CA - but last resort. This weekend I'll re-do the position and calibration with compass in hand and publish the results.

Mine is a four-wire with a DB9 connection - little black box with the DB9 pointing out the back side - opposite direction of flight.

I'll let you know the results Monday - gotta rebuild the right brake system first before I can taxi again.

Thanks

Some compositions of SS are magnetically active, although usually not. Did you test the screws with a magnet? Or try brass instead?