by dedeleco » 23/03/10, 13:19
I did not expect to excite with the earth connection, which is probably not crucial.
I give my past personal experience.
One case where the earth electrode is working, (without a 200000V line or neighboring tram) is when lightning strikes in the vicinity. It induces (inductive and capacitive) even at 100m enormous voltages and currents throughout the house, and then we can have much more than 2A in transient a few microseconds and the whole house rises in voltage with corresponding destruction, like VMC with burnt motor, (repetitive personal case) despite the 30mA which does not jump fast enough !!
Once on my house, lightning made a hole, set fire to and destroyed the meter, the circuit breaker, the fridge, the hob but not the TV, the computer which saw its socket torn off !!!! !!
The radio and microwave emissions do the same in smaller, being able to disturb, if there are defects in the shielding, the decoupling of the power supplies (bad decoupling capacitor, badly welded, or badly placed, too far from the microprocessors, etc.). )
A simple thyristor thermostat or heater (coffee maker), even at a neighbor's, poorly suppressed (even at a neighbor's) generates appalling disturbances (1KW HF transient) in the entire neighborhood and could be enough to be the cause !! A small test is to watch TV and see the disturbances on the screen (same TNT and analog) in strong form (loss of the image one second) or weak (streaks on the screen). At home I have such disturbances on the TV every 10min and I know that a neighbor has a poorly suppressed thyristor regulation surely !!!
But as I have no more problem, I support !!
Also it is necessary to pinpoint the problem by testing each single single element isolated, collect clues without preconceived ideas not proven by overlapping evidence, considering all possibilities, like a detective.
An oscilloscope can be very useful in showing the nature of the parasites, 50 or 100Hz or HF or pulses in microseconds !!
Okofen if under guarantee, must be able to provide it or take it on loan, or buy it inexpensively, a few hundred euros.
But it is necessary to know a little practical electromagnetism, because otherwise one can make a mistake by taking what is normal for a defect !!! You have to know how to explain why any 1m end of wire put in an oscilloscope gives oscillations and especially understand how they vary (a presence detector!).
I have a small thermometer at PT100 and I used it to measure the temperature of the sea, which with the salt has oxidized the contacts, so that it often measures with fluctuating errors (T increases variable with the contortions on connectors) if the connectors are not stripped of oxidation !!
In this case, I really went overboard with seawater! and therefore very unlikely for you !!
0 x