A test on the interference of IST8310, RM3100 and Permalloy to the compass

Hi,guys.
I used V5+ as a flight controller, and the built-in compass was severely disturbed. I recently got a CUAV Nora, which uses RM3100 as a built-in compass. I want to test whether its anti-interference performance has really improved, and I also want to explore whether Permalloy can reduce a certain compass interference.
(Note : Because the continuous rain, I reverse the blades of the copter so that the copterwill not fly even if the throttle is pushed up. Therefore, the test is conducted on the ground. Please do not imitate my behavior at will. It is not verified by flight. Time-proven)
This is my copter, it is very beautiful ( hahaha )


This is its internal structure, very concise

This is how I installed the flight controller ( I forgot to take the picture on the test day. This picture is for your reference. I am too lazy to connect the wire again… )

My test standard is to observe the interference of the Compass Motir Calibration ,The official Ardupilot document recommends that it should not exceed 30% .

I used V5+ flight controller for the first test and did not do any shielding measures. It can be seen that when the throttle is about 43% , the current is 6A , and the interference is 93% . The second picture is a simple repeat test, which shows that my test is repeatable and reliable .


In the second test, I used the Nora flight controller, and did not do any shielding measures. It can be seen that when the throttle is about 55% , the current of the copter is 14A, and its max interference is about 24% (In normal circumstances, I should keep the throttle consistent, but the anti-interference performance of the RM3100 is so good that I I thought I got a wrong result, so I pushed the throttle higher)

Before the third test started, I disassembled the aircraft and used Permal to cover the switchboard to shield the magnetic field. Permalloy is a metal that can shield the magnetic field, so it will also shield the earth’s magnetic field. The correct way to use it is to use it to shield some of the larger interference sources from a certain distance. As long as it can reduce some of the interference, it has reached the goal. It is unrealistic to use it to shield all interference. When the area used by Permalloy is too large, the calibration will not pass, and the value of an axis may be very large. The installation method is similar to the picture below. I used a piece of paper for short circuit isolation caution! There is a risk of short-circuiting at random like this!

My third test still used V5+ flight controllers, but this time I used Permalloy shielded switchboards. When I push the throttle to about 50% , the current of the aircraft is about 10A , and the maximum interference is 55%.

In the fourth test, I replaced the V5+ flight controller with Nora , and used a permalloy shielded power distribution board. When I push the throttle to 50% , the current is 11A , and the maximum interference is 10% ! What a great test result


I used a table to summarize this test.

As can be seen from the table, the interference ratio of the switchboard in my plane is very large, but because my rigorous testing, I cannot get a specific ratio. Another use of RM3100 is Nora , its built-in compass great resistance to interference. Because when V5+ under 43% throttle, the interference has reached 93% , while Nora is under 55% throttle, the max interference is only 24% !

Certainly interesting results. I think that the use of the permalloy in such close proximity to the magnetometer (such as with the Nora FC) is likely to give you problems that will not be highlighted with the Compass Motor Calibration test. Another interesting test would be to report the actual orientation vs reported orientation for various orientations with the permalloy in place.

From the theory, you may be right, because it will cause the compass to measure the earth’s magnetic field is not completely accurate. In further testing, I found that it will cause the 8310 Z axis value to be abnormal, the value exceeds 1000. Wait for me to pass a few When the sky is free, I will do another flight test.

I think you should test flying copter. I have some experience with RM3100 in my new octcopter and I see that there is no huge difference in anti-interference capabilities of RM3100 (Drotek Sirius) compared to compass installed in HERE+. Still with 2x 14000 6s Lipols compass must be 15-20 cm from batteries. If Sirius is closer to batteries I get error messages during higher currents draw.

This is a very difficult range to define. If you are close enough, there is no effect of any compass, including rm3100. I have used it to test on PDB distribution board, even the current of 10A will have a very bad impact, but if you observe the recovery speed or offset value, rm3100 has a better improvement than 8310. Maybe I need to use a magnetometer to accurately measure the magnetic field strength and the interference strength of the compass? But this is too professional, I will not do it

My RM3100 from Drotek was faulty After repair I get much better results from it.