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541 views
08:22 Jan-17-2002

Massimiliano Pau

Teacher, -
Univ. of Cagliari, Dept. of Mechanical Engineering,
Italy,
Joined Sep 2002
25
Problems with electromagnetic fields

Dear friends

I'm carrying out some UT immersion test on a aluminium wheel driven by an electric motor.

Unfortunately the signal is very disturbed by "spikes" generated by the motor. Any suggestion in order to reduce (or eliminate) this problem?

Thanks in advance

Massimiliano Pau


 
00:42 Jan-17-2002

Joe Buckley

Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT,
United Kingdom,
Joined Oct 1999
515
Re: Problems with electromagnetic fields Simple things to try

1. Move or Shield the power to the motor - make sure the motor wires are not less than 10cm from the probe connections. Check grounding etc. - Thry linking the probe body to the motor case. If its already joined try disconnecting it (These things are seldom rational until you've solved them)

2. Put some capacitors across the motor contacts - 0.1 uF low impedance type should reduce most spikes. Wrap the power leads round a toroid or use series inductors

3. Move the motor - Drive the mechanism via a belt and pulleys (Usually necessary anyway to keep the motor out of the water)

4. Make Sure the motor power supply is not contributing - Some switched mode power supplies can kick out a lot of noise.- Do you get spikes when the voltage is reduced and the motor not turning? If so its not the motor...

Good luck

Joe


4. If all else fails use an AC shaded pole motor or similar -


: Dear friends
.
: I'm carrying out some UT immersion test on a aluminium wheel driven by an electric motor.
.
: Unfortunately the signal is very disturbed by "spikes" generated by the motor. Any suggestion in order to reduce (or eliminate) this problem?
.
: Thanks in advance
.
: Massimiliano Pau
.



 


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