Volume 2, Number 4

October 2003

 

TNT Tips:

Water Condensation in Printed Circuit Boards
Had one of those days when you walk out of an air conditioned building and the humidity fogs the lenses in your glasses? The lenses soon normalize as they warm to air temperature. The same thing happens to printed circuit boards in portable instruments under the same conditions. A film of condensed water coats the circuit boards. If the boards are clean and internal voltages are low, instruments will continue to work satisfactorily and, after normalizing to the new environment, will never show that water condensed inside. However, in older instruments with just a little dirt on the boards and a higher voltage in the circuits, internal arcing easily occurs and can shut the instrument down. Arcing, usually characterized by glitches and the complete disappearance of the display, can be recognized by sudden abnormal operation. The trick is to recognize  conditions causing the problem (high humidity outside versus cold dry air inside) and to allow at least 45 minutes for normalizing before use when the instruments are taken outside. Flaw detectors and portable detectors are the units primarily affected by this phenomenon. If cleaned internally and sprayed with the proper coating, chances of arcing will lessen.

L. Byron Makarwich
Friendswood, Texas

 

Avoiding Tangled Lines
Disposable plastic fishing line spools can be used as inexpensive and effective transducer cable storage reels. After transferring the fishing line to your reel, save the empty spool. Cut two cable diameter-sized slots in the rim of the spool from the edge to the hub. These slots will hold the cable in place. If you leave about an inch (25 mm) extended when wrapping the cable, you’ll be able to carry out a cable and transducer functional check without removing the cable from the spool.

Bill Perrin
Fredericton, New Brunswick
Canada

 

[ The NDT Technician ]

 

 

---

 
Copyright © 2009 by the American Society for Nondestructive Testing, Inc. ASNT is not responsible for the authenticity or accuracy of information herein. Published opinions and statements do not necessarily reflect the opinion of ASNT. Products or services that are advertised or mentioned do not carry the endorsement or recommendation of ASNT.

IRRSP, NDT Handbook, The NDT Technician and www.asnt.org are trademarks of the American Society for Nondestructive Testing, Inc. ACCP, ASNT, Level III Study Guide, Materials Evaluation, Nondestructive Testing Handbook, Research in Nondestructive Evaluation and RNDE are registered trademarks of the American Society for Nondestructive Testing, Inc.

ASNT exists to create a safer world by promoting the profession and technologies of nondestructive testing.