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Up Topic Welding Industry / Inspection & Qualification / High freq and UT
- - By fbrieden (***) Date 11-06-2009 18:31
Using my 58L at school today and noticed random signals on the screen when ACHF was being used for welding. Have any of you ever experienced this situation?
Parent - - By ravi theCobra (**) Date 11-06-2009 19:55
Yes  the coaxial cable has some of the RF  leaking in  -
Parent - By fbrieden (***) Date 11-09-2009 02:12
New cable; perhaps not connected all the way?
Parent - - By 3.2 Inspector (***) Date 11-06-2009 20:25
I am sure that CWI555 will come by and give his input.

3.2
Parent - - By CWI555 (*****) Date 11-07-2009 16:58
Actually no. He's already figured it out and looking for confirmation. He got that already.
Parent - - By 3.2 Inspector (***) Date 11-08-2009 19:38
Can't you atleast quote some code stuff ?

3.2
Parent - - By fbrieden (***) Date 11-09-2009 02:11
Guys....doing calibration procedures with my seniors....picked up "ghost signals" while doing so...just wondering if any of you experienced this type of event!
Parent - By CWI555 (*****) Date 11-09-2009 02:57
Ghost signals can be from EMF interference, a refresh rate that is to fast/improperly matched send/receive, or interference patterns.
It's actually not an unusual event. I've run into it many times scanning on structural steel with welders nearby.
Parent - By mroach (**) Date 11-09-2009 19:06
Even a new cable may not have the insulation needed to shield the EMF. Try covering the reciever jack on the front face of the 58L with electrical tape. That should help. If the interference is still there, then you may have to move to a new location or find a way to shut down the source. Yes, this type of interference is very common around welding machines or cranes.      
Parent - By CWI555 (*****) Date 11-09-2009 02:54
He was already on the right answer. Code stuff is simple enough, have to be able to interpret the signals.
ASME V 2007 Fig T434.3 calibration block for pipe (notes)
"(e) Notch lengths shall be sufficient to provide for calibration with a minimum 3 to 1 signal-to-noise ratio."
Any electronic device is prone to EMF interference, this is why faraday cages are built around welders when they have to be in radio sensitive areas.
Hi freq units are especially prone to this.

Your S:N ratio is the key.

Regards,
Gerald
Up Topic Welding Industry / Inspection & Qualification / High freq and UT

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