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Inductance and sensitivity ?

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Externet

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A circuit involving a coil -with say 5000 turns, 10cm long, 2cm ⌀ soft iron core, - feeding a differential amplifier inputs is to detect a spinning magnet at a distance.

Replacing the core with mumetal the inductance will increase ~100 times due to the permeability factor.

Increasing the inductance that way, can the spinning magnet be detected from a greater distance ?

Would a longer core of mumetal in the same coil increase the sensitivity even more ? I see no core dimension in the formula.
 
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Sceadwian

Banned
What kind of distance are you trying to sense? Industrial inductive sensors generally don't go more than a few centimeters in distance because of noise problems.
 

Externet

Well-Known Member
Thanks for responding. :)

The ambient noise is not a problem IF appears, as there is another identical coil connected to another differential op-amp that senses most EMF that can show up and cancels it in common mode (instrumentation amplifier) This is not a common industrial sensor; it is a gradiometer.

The distance is not important if 10 cm or 10m; am trying to find out if by replacing the iron cores with mumetal, the sensitivity will increase any amount as the inductance increases. :confused:
 

Sceadwian

Banned
If the sensors have physical separation you can't rely on common mode noise rejection for all frequencies, especially if it's read differentially. Such a setup would make a very good antenna at certain frequencies, especially with modern high frequency transmitters. What's your coil seperation distance?
 
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Externet

Well-Known Member
Coils are rigid coaxially aligned 5 metres apart. Want to improve detection distance of magnetic anomalies moving at least 25 metres from one of the coils.
I believe with such high inductance values, the device is very deaf to high frequencies.
 

Sceadwian

Banned
You'll pick up plenty of EM interference just fine. What exactly are you trying to measure? 'magnetic anomalies' is more than a little vague. If you want more sensitivity make bigger coils.
 
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