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Technical Discussions
Chad
Chad
02:39 Jun-12-2008
UT transducer connecting

I seem to recall being told one time that you should not connect your transducer to your flaw detector while the machine is on. Is this correct or does it not matter one way or the other?


 
 Reply 
 
Michel Couture
NDT Inspector,
consultant, Canada, Joined Sep 2006, 893

Michel Couture

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
893
07:03 Jun-15-2008
Re: UT transducer connecting
Hi Chad,

I've been told the same by someone at one time who was told also. Personnaly, I don't know if it makes much difference. I'm sure someone else will write with their opinion as well. The reasons I see not to do so are as follow: If you are working in an environment where the danger of explosion exist. I have personnally notice the little spark when you connect your transducer (specially with a microdot connector). So, there is a danger there. I don't know about your industry, but it is not something you want to try in an aircraft fuel tank.
The other reason would have to do with the computer inside the UT instrument. Same as for our PC at home, sometimes you have to reboot your PC for any changes you've made to take effect. I'm speculating here, but I wouldn't pass it by some IT guys to want to do it that way.

Cheerios,

Michel

----------- Start Original Message -----------
: I seem to recall being told one time that you should not connect your transducer to your flaw detector while the machine is on. Is this correct or does it not matter one way or the other?
------------ End Original Message ------------




 
 Reply 
 
Linas Svilainis
R & D,
Kaunas University of Technology, Lithuania, Joined Nov 1998, 67

Linas Svilainis

R & D,
Kaunas University of Technology,
Lithuania,
Joined Nov 1998
67
09:52 Jun-16-2008
Re: UT transducer connecting
----------- Start Original Message -----------
: I seem to recall being told one time that you should not connect your transducer to your flaw detector while the machine is on. Is this correct or does it not matter one way or the other?
------------ End Original Message ------------
If you are speaking about passive probe, this requirement is probably for safety issues.
1.The connector (BNC,SMA ) that is usually used to connect transducer to equipment is not designed for "pre-mating earth".
2.Not all equipment have a galvanic isolation of "hot" center tap.
This means that there is a possibility to connect a center tap first. In such case the operator can get electrical shock.
Speaking of active probe (with preamp inside or array) this requirement is applicable for equipment that is not designed for "hot plug".
Despite everything said people DO CONNECT transducers while equipment is on and no one was seriously hurt or equipment damaged.
My advise would be to follow this rule.

regards,

Linas




 
 Reply 
 
Tom Nelligan
Engineering,
retired, USA, Joined Nov 1998, 390

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
04:57 Jun-16-2008
Re: UT transducer connecting
With typical commercial flaw detectors and thickness gages, there is no reasonable likelihood of either personal injury or damage to the instrument. While it is certainly possible to get a spark -- a very important issue if you're working in a combustible environment -- typical spike and square wave excitation pulses from portable instruments pose no shock hazard under normal conditions.

There may be some nonstandard instruments out there that represent an exception, so if you want to err on the side of caution, act accordingly. But in 30 years of working in ultrasonic NDT I've never heard of this being a safely problem, combustible environments excepted.

----------- Start Original Message -----------
: I seem to recall being told one time that you should not connect your transducer to your flaw detector while the machine is on. Is this correct or does it not matter one way or the other?
------------ End Original Message ------------




 
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