Air core coil design and test.

[cxf208]

Hi:
I have designed an air core coil sensors with a diameter of 50cm, 60 turns. The inductance is about 3.6mH. I use a frame of ABS material.
Here are the questions. When I connect the coil to an oscilloscope, there are noises of 50Hz. But when I switched the connectors, the noise of 50Hz is suppressed obviously. I changed nothing except for switching the connectors(from ++, -- to +-, -+.). It seems that the coil sensor has a different filter for the magnetic fluxes crossing it.
I don’t use any shield, just test it in my office.
Can anyone tell me the possible reasons of this phenomenon?
Thank you!

 

[vfone]

When use +-,-+ the fields are cancelled, and also the noise..

 

[cxf208]

When use +-,-+ the fields are cancelled, and also the noise..

Yes. I know this. I seems the ABS material is not that pure, which causes the problem. Thank you all the way.

 

[biff44]

Hi:
I have designed an air core coil sensors with a diameter of 50cm, 60 turns. The inductance is about 3.6mH. I use a frame of ABS material.
Here are the questions. When I connect the coil to an oscilloscope, there are noises of 50Hz. But when I switched the connectors, the noise of 50Hz is suppressed obviously. I changed nothing except for switching the connectors(from ++, -- to +-, -+.). It seems that the coil sensor has a different filter for the magnetic fluxes crossing it.
I don’t use any shield, just test it in my office.
Can anyone tell me the possible reasons of this phenomenon?
Thank you!

are you in a country where the line voltage in is AC at 50 Hz?