Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

magnetic field noise

Status
Not open for further replies.

rocsavi

Newbie level 3
Joined
Mar 25, 2015
Messages
3
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
29
dear all,
I worked on PHOTODETECTOR based project...In this project,input light from laser is coupled through fiber ....Near photodetector i have to place a coil near photodetector pcb ...there is no physically contact between photodetector pcb and coil...coil is driven by a function generator..when coil vibrates at desired frequency which is set by function generator..pcb also pick up same frequency signal and gives this as output..
pcb contanis LT1167 Amplifier which gives output,,,problem is that, frequency of required output signal and coil vibrating signal frequency both are same..i want to avoid coil signal that is captured by pcb...any suggestion p[lease...
 

biff44

Advanced Member level 5
Joined
Dec 24, 2004
Messages
4,972
Helped
1,369
Reputation
2,734
Reaction score
1,045
Trophy points
1,393
Location
New England, USA
Activity points
37,361
schematic needed to comment. you need to use a differential amplifier to null out the coil noise...not sure if it is magnetic pickup or ground loop problems.
 

volker@muehlhaus

Advanced Member level 5
Joined
Apr 11, 2014
Messages
2,749
Helped
1,017
Reputation
2,040
Reaction score
1,034
Trophy points
1,393
Activity points
17,685
Minimize the area where magnetic flux can couple into your signal/return path.
Example: twisted wire pairs minimize the sensitivity to external magnetic fields: the area between wires is small and by twisting we try to cancel the induced voltage from an external field.
 

vfone

Advanced Member level 5
Joined
Oct 10, 2001
Messages
5,437
Helped
1,566
Reputation
3,135
Reaction score
1,177
Trophy points
1,393
Activity points
34,483
On top of using twisted pair wires, and to minimize even more the induced voltage from the external field, you can twist the wires on different layers on the PCB.
You can check the net for ideas, I've seen some granted patents on this matter.
 

chuckey

Advanced Member level 5
Joined
Dec 26, 2010
Messages
4,863
Helped
1,309
Reputation
2,624
Reaction score
1,284
Trophy points
1,393
Location
Southampton and holiday cottage in Wensleydale (UK
Activity points
31,695
With no laser signal, inject a bit of the magnetic field energising source into the amplifier. Adjust its amplitude and phase to minimise the amplifiers out put. Switch on the laser, the output now comes just from the laser.
Frank

- - - Updated - - -
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top