EMF effect on CRT monitor

flickering

It took three

finally been

problem for anybody

scale, and

nearly always above

consistently in the

the strength of

believe us at first

experts agreed with

surprisingly,

announced that they'd

there were

readings are now

levels of EMF

flickering

of been

eyesight was to

Thanks for the details... I am curious about how the excessive EMF was generated by bad connections... arcing etc maybe but then you'd think the power would have been so dirty that ruined electronics. I think there is something else that went on .

Phil Scott

>

10mG (1uT). Frequently they rose above 30mG (3uT) and consistently in the 15mG-25mG (1.5uT-2.5uT) and the flickering corresponded to the strength of the field at any given time. The electric board didn't believe us at first that this was the problem, but eventually one of their experts agreed with our diagnosis. They told us to take readings for a week, and surprisingly, 24 hours after returning the readings to them, they announced that they'd fixed the problem and thanked us for our patience. Turns out there were some bad connections that they replaced somewhere. The readings are now down to around 10% of the readings I gave previously. I can't say I'm glad about the six month exposure to those levels of EMF radiation (September-March), or the eye strain caused by the flickering monitor for this period of time, but the problem appears to of been resolved. Thanks to those who helped out, even those who believed my eyesight was to blame :) Regards, Pan Thanks for the details... I am curious about how the excessive EMF was generated by bad connections... arcing etc maybe but then you'd think the power would have been so dirty that ruined electronics. =A0 I think there is something else that went on . Phil Scott

I agree: It sounds like there was a low frequency condition for some reason, as if in a serious voltage drop near to a cutoff or dangerous level (speculating -100vac) I believe the high emf would come from the monitors/equipment trying to compensate for the low voltage/frequency condition. Roy Q.T.

I agree: It sounds like there was a low frequency condition for some reason, as if in a serious voltage drop near to a cutoff or dangerous level (speculating -100vac) I believe the high emf would come from the monitors/equipment trying to compensate for the low voltage/frequency condition. Roy Q.T.

------------------

Low frequency and/or low voltage causing a 10X increase in EMF (magnetic field in this case)??!! Boy would I like to see your references for that fantasy.

Charles Perry P.E.

I agree Phil. A bad connection should be the cause. Since he was measuring magnetic field increases, I would say arcing didn't do it either. The only bad connection I can think of that might increase the field strength in a localized area would be a loose primary neutral. I have seen cases where the return current will flow on municipal water lines. Since you are often closer to the water lines than your are to the neutral conductor, you see a greater field strength. For those in the group that might not know: for a given current, the field strength drops as the square of the distance from the conductor.

Charles Perry P.E.

In the vein of the truth

I had a customer that had flickering in their monitors inside a university building. They non-scientifically figured out that if the monitor was moved to the end of the cord, 3 feet the problem went away. I eventually traced the problem to a addition neutral ground connection that should not have existed.

No, that clearly wasn't the cause. I found the highest readings on the road outside, where it was normally between 75mG (7.5uT) and 125mG (12.5mG), and sometimes even over 150mG (15.0uT).

Regards,

Pan

The electric board did mention arcing as a possible cause, but haven't elaborated since. I wouldn't be at all surprised if they have lied about the true cause, probably it was something much more serious. However, it was quickly fixed, so obviously nothing fundamental.

If it helps, the readings were constantly fluctuating, probably with current changes. Sometimes the readings would change so much in a minute that it was pointless taking them at all. It seemed worse at certain times too, most notably after 11.30pm.

The field strength did drop off quite rapidly indeed, however it was so high that a strong reading could be obtained throughout the entire house. At the door, it had dropped out by about half, another half into the middle of the house, and probably another half towards the back.

What concerns me about this whole affair is that they didn't believe us when we determined that magnetic fields were the problem. They insisted the problem was being caused by something else, even though they couldn't determine what. It was only by chance that one of their experts said he had seen this before and agreed with us that the problem was eventually uncovered. The laughable thing is that we are not electricians and they are supposed to be experts. If they had just tested our theory to start with, a lot of time could of been saved.

That's mainly why I've posted this thread, to give others an idea of a possible cause for this problem if anybody gets it in the future. In my search of Google Groups before we fixed it, I could find no direct mention of anybody suddenly developing this problem in a house.

Regards,

Pan

Didn't anyone take Voltage & Current measurements ?

I agree: It sounds like there was a low frequency condition for some reason, as if in a serious voltage drop near to a cutoff or dangerous level (speculating -100vac) I believe the high emf would come from the monitors/equipment trying to compensate for the low voltage/frequency condition. Roy Q.T.

------------------ Low frequency and/or low voltage causing a 10X increase in EMF (magnetic field in this case)??!! Boy would I like to see your references for that fantasy. Charles Perry P.E.

------------------------------

I already explianed why i thought of that in my reply.OR: Perhaps they were trapped in a temporary dimensional riff and the monitors flickered because in the 3rd & fourth dimension, like when you look at a Monitor through a Television Cameras View, thet Seem to flicker.... [unbeknownst to them] It took the Super Heroes of the Utilities Company to bring them back to reality., had they fallen into the Vortex they would have been doomed, lost forever };-) wanna here another Fantasy ? Roy Q.T.

------------------ Low frequency and/or low voltage? >snip Charles Perry P.E.

------------------- No, that clearly wasn't the cause. I found the highest readings on the road outside, where it was normally between 75mG (7.5uT) and 125mG (12.5mG), and sometimes even over 150mG (15.0uT). Regards, Pan

------------- For that to have been the case, I believe there may have been a Odd Voltage/Current/Frequency condition as well, affecting everything nearby., you can't prove this wrong unless someone took respective measurements into consideration.The Ambient surroundings just doesn't flux off high EMF's without a cause for effect.A loose neutral cable or worse may have been the culprit. maybe they installed a new substation and didn't have adequate shielding and didn't get it until the monitor symptoms & subsequent protests. Roy Q.T.

I would guess that most people reading this group are tired of your fantasies. Perhaps you could try reality for a change.

Charles Perry P.E.

Shielding in a new substation? "Ambient surroundings just doesn't flux off high EMF's" Where do you get this stuff?

I have heard of shielding indoor transformer vaults, but substations?

Magnetic fields are caused by current flow. Find the high current and you find the source.

Charles Perry P.E.

On Tue, 08 Mar 2005 11:43:23 -0500, Roy Q.T wrote

Well, they did measure supply voltage/current/frequency into the house and found nothing wrong. They wrote to us after installing a meter for a week and told us that nothing was amiss. This was a month or two before we tracked down the problem ourselves.

Regards,

Pan

Thankfully as you say, tracking down the location of the cause was extremely simple. The readings were highest along a seam of tarmac located in a middle of the road. Clearly from an underground source. I've lived here a long time and I remember when they first installed it, so it was fairly obvious.

Regards,

Pan

Shielding and Fantasy< Roy Q.T. Shielding in a new substation? "Ambient surroundings just doesn't flux off high EMF's" (MY POINT EXCACTLY) Where do you get this stuff? I have heard of shielding indoor transformer vaults, but substations? Magnetic fields are caused by current flow. Find the high current and you find the source. Charles Perry P.E.

I am starting to have serious doubts about you Charles Perry P.E. First; the Dimensional Theory is a part of Quantum Physics.[mentioned it just to humor you all] Second: Concrete Structures containing High Tension Distribution Equipment and serving the pupose of a Substation will have a High Electromgnetic Field emanating from it, Shielding Curtails (or minimizes) the Outward Force of These Fields out into the Public which is a Newly Tested & very Real Perturbance & part of Life in Big Cities.

~ Roy Q.T. ~

But you have not explained what caused you to suspect this & buy the meter. Do you know where the repaired connections were with respect to your house & how they came to be creating a varing magnetic field. Were your neighbours similarly affected. Congratulations on your sticktoitiveness. Pete

My apologies. I will answer your questions below

The reason I suspected that the cause may be from an electric/magnetic field is because I had seen similar effects before. I have spent many years in a computer field and had noticed that if a speaker is placed too close to a monitor, it will show up as a flickering effect on the screen. Initially, I believed the magnetic effect of the speakers themselves was causing the problem. However, I later realised that it was the power-supply in the speakers itself that was causing the effect. My speakers do not use an AC plug adaptor to power them, rather an internal power supply. Having seen a similar effect (but much weaker), I suspected that magnetic/electric fields may be the cause of the problem.

I'm not sure what they repaired yet, and where they even conducted the repairs, but I'll find out shortly (assuming they are honest). I'll let you all know. I would think the changing field strength was being caused by shifting current levels underground beneath my street.

My neighbours were indeed similarly affected, but unfortunately none of them used CRT monitors and therefore had not noticed the effect. However, my meter clearly showed similar readings in their houses. The underground power for this road runs down the entire street, so everybody was affected. I took a monitor to a house in another street and it showed no flicker. In addition, the readings were extremely low, lower than they even are now here.

Hope this helps you.

Regards,

Pan

I'm just wondered what EMF readings other people on the newsgroup get in their homes. The front of my house is currently reading about 4.2mG (0.42uT). Is that pretty average, or is it fairly high in comparison to most houses?

Regards,

Pan