lightining effect on instruments

  • Thread starter karthikeyan santhanam
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karthikeyan santhanam

i need to know the effect of lightining on instruments generally and specifically on SMART type transmitters.

anybody, pl help me.

Jake Brodsky

I'm assuming you're refering to how durable these instruments are for surviving a lightning strike.

If you grounded it correctly, there shouldn't be any effect whatsoever. Obviously, if you get hit with a direct strike, all bets are off. However, in over 15 years as a technician and an engineer in the field, the vast majority of lightning problems I have seen were not due to direct strikes and instead caused by nearby strikes and a ground loop.

If you live in the US, consult the National Electrical Code for reference on how the electrical system is grounded. Many ground loops are the result of some well intentioned, but poorly implemented efforts at keeping instrumentation and electrical grounds completely seperate.

Again, people make careers out of a subject like this. The concepts aren't difficult. The legalities and the applications are usually the issue. Consider any time spent studying this subject as a down-payment toward a much more reliable, and surviable system.
Lightning _hurts_.

Although there are well-accepted ways of protecting instrumentation from the effects of lightning, they are not always effective.

I once installed a downhole level sensor in the middle of the Nevada desert where the tallest thing for 30 miles was the deepwell pump sitting next to the pump control panel on which the level transmitter was mounted.

There was a good lightning rod, connected to a good earth ground.

So, the lightning passed through the rod, into the ground, up the ground leg into the MCC, and blew the circuit boards in the MCC and the level
instruments into plasma, depositing the traces on the front and back interiors of the enclosure.

In the United States, especially in Florida (lightning frequency capital of the universe) the best defense is a good fault alarm and shelf-spares.

Walt Boyes
editor, The Instrumentation Reference Book, 3rd Edition, 2001
available at, and other fine technical book

Walt Boyes -- MarketingPractice Consultants
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Keep the grounding electrode conductor (rod to circuit/equipment ground conductor ) as short as possible so as to minimize cable impedance, which
will be significant when coupled with lighting strike current(s) [V=IxZ].

Brett Haas


gerald beaudoin

I have always employed all of the accepted techniques for lightning protection and that is what lets me sleep well at night. However, I am
not convinced that any or all of the devices used will eliminated all of the damage from "the big one". They may limit the damage and I guess that is all you can hope for when you are dealing with such huge amounts of energy and increasingly sensitive components. Trying to predict exactly what damage will be done by a strike or near strike is interesting work but far from an exact science. My advice: Do everything you can to prevent spikes at the entry points; phone lines,
cables, power sources, antennae etc......but still keep those mission critical spares on hand.

Good Luck.....because thats what it is!

Gerald Beaudoin

Responding to Brett Haas' comment:

If the grounding conductor is in an intact metal conduit for mechanical protection, the conduit should preferably be of non-ferrous material. If
the conuit is constructed of ferrous material, then both ends of the conduit must be bonded to the grounding conductor.

Phil Corso, PE
(Boca Raton, FL)