An MOV is a Metal Oxide Varistor - usually looks like a thick ceramic
disk capacitor. Their characteristic is that when a voltage higher than
180 volts is applied, they start acting as a short circuit. By "shorting
out", they protect your equipment from the surge. How much energy they
can tolerate before burning out themselves is the joule rating. All MOV
devices have a rating that indicates how many joules they can absorb.
The problem is that not all manufacturers of the power strips give the
consumer the rating of the MOV devices that they use inside. Thus, a
high-quality surge protector could have a much higher rating than a
cheap one you buy at a discount store. How is a consumer to know? Caveat
emptor.

I do not know of a way to test if an MOV has been damaged or not. If you
know that there was a surge, then you may want to decide if your
equipment is worth spending the money for a new surge protector. Note
that a UPS does not provide surge protection unless it has an MOV in it,
or if it is an ONLINE type (much more expensive - most are standby).

Peter
____________________________________________________________
Peter Shkabara P.E. - Computer Science Instructor
Columbia College - 11600 Columbia College Drive - Sonora, CA 95370
(209) 588-5156 - [log in to unmask] - http://gocolumbia.org/pesh


-----Original Message-----
Thanks,  I haven't heard of joule rating as a standard, although I
remember joule units from physics class.  What I see on specs for surge
protectors is MOV, which I don't know what that refers to (v probably
stands for voltage).

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