Many years ago I subscribed to Popular Electronics Magazine.
since then I have moved twice and lost most of my old issues.
Anyway, one issue dealt with making a home made magnetometer to sense the change in the local earths magnetic fields as it bent around metalic objects as they moved. It used a pair of neon transformer secondary coils on a soft iron bar for the reciever.
It then took the microscopic induced voltage generated in that coil assy and amplified it to a level that could be heard with a regular set of headphones.
there was a very high gain ultra sensitive op amp used in the first stage.
Does anyone have that circuit? or know of how that circuit can be built?
I thought it would be a neat toy to let the local elementary kids play with and get a better understanding of how the earths magnetic field moves around in their Earth Science class. Or just for me to play with too!
since then I have moved twice and lost most of my old issues.
Anyway, one issue dealt with making a home made magnetometer to sense the change in the local earths magnetic fields as it bent around metalic objects as they moved. It used a pair of neon transformer secondary coils on a soft iron bar for the reciever.
It then took the microscopic induced voltage generated in that coil assy and amplified it to a level that could be heard with a regular set of headphones.
there was a very high gain ultra sensitive op amp used in the first stage.
Does anyone have that circuit? or know of how that circuit can be built?
I thought it would be a neat toy to let the local elementary kids play with and get a better understanding of how the earths magnetic field moves around in their Earth Science class. Or just for me to play with too!