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CRT monitor radiation measurement project

Discussion in 'General Electronics Discussion' started by regulaz, Jan 4, 2013.

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  1. regulaz

    regulaz

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    Jan 4, 2013
    hi im new here so hello fellas!

    i'm using an old school 21 inch CRt monitor as those used in graphics industry around 6 years ago.

    i was curious about how much radiation it was actually outputting.

    there is an anti radiation screen in front of this with a grounding cord which goes into the ground of the electrical outlet.

    i took a multimeter set it on AC 2 volts setting and it measured 300 millivolts.

    now im curious if this is actually the electric radiation being measured or is this something else?

    does this prove the anti radiation screen is necessary for CRT type monitor?

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    one more question my 29 inch CRT TV has a 2 pronged plug and measured in the same way as above shows 40 volts... the cable box when turned on increases this 40 volts figure to around 100-200 volts fluctuating. when i touch the base of the cable box with one lead and the ground with another lead it read 90 volts.

    it looks a little dangerous to me, but im not sure if im measuring the radiation or something else. i have 220 volts 50 hz power system here.

    thanks.
     
  2. GreenGiant

    GreenGiant

    842
    6
    Feb 9, 2012
    The screens dont produce much of any radiation, the old myth about rotting your eyeballs by sitting too close started in truth... but you have to be less then 2 inches away and watch non-stop for about 15 years before there is even the beginning of radiation damage.

    Where did you have the lead of the multimeter placed when reading this 300mV?
     
  3. regulaz

    regulaz

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    Jan 4, 2013
    one lead in the electric outlets ground and one lead touching the ground cord of the radiation filter.

    in the 3rd last pic you can see the ground lead of the filter http://www.tigerdirect.com/applicat...ffiliateID=rGMTN56tf_w-j5A6Z8LpNziDfvEGjywJuA
     
  4. GreenGiant

    GreenGiant

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    6
    Feb 9, 2012
    That is not specifically a radiation filter, it has radiation filtering properties, the voltages you are reading are more likely from static buildup on the screen not radiation
     
  5. regulaz

    regulaz

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    Jan 4, 2013
    the 21" monitor has no static on the screen front.. the 29" TV does have a lot of static.

    howcome when the cable box is switched on the measurements on the TV go from 40 volts to 200 volts?
     
  6. Jotto

    Jotto

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    Aug 24, 2012
    The federal government required companies to make sure that if a fault in the HV section to shut down instead of allow the voltage to go higher, thus was born the xray protection circuit. The public outcry concerning radiation leakage from a TV forced the government to require manufactures to design a circuit to control the HV, if a fault was detected it would shut down the unit. Zenith was the first company to design a circuit, which had problems due to the manufacture of 4 leg capacitors using a cheaper product then the one Zenith had spec'd out.

    The shadow mask of the CRT controls the electrons and the stray electrons.

    The picture you referenced is a LCD unit privacy screen, the only HV is the inverter for driving the lamps. There is no radiation concern with a LCD. An now the new ones with LEDs there is no HV.
     
    Last edited: Jan 4, 2013
  7. regulaz

    regulaz

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    Jan 4, 2013
    i got a figure of 1 volt for tco compliant lcd with ccfl backlght and 1.5 volts for led backlit monitor. only 300 millivolts for crt with tco 95
     
  8. Jotto

    Jotto

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    Aug 24, 2012
    There are two different acceptable standards, one is 200mv and the other is 300mv. But the reading isn't emissions of rf, its the voltage on the skin of the machine in question.

    What I test for is leakage on the metal chassis. Sometimes we get a complaint that the a machine shocked the customer, so I test to make sure its within acceptable limits.
     
  9. regulaz

    regulaz

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    Jan 4, 2013
    hi thanks for your reply. can you tell me what is the name/link of the standard which says 200mv or 300 mv is ok on the skin of the machine?
     
  10. Jotto

    Jotto

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    Aug 24, 2012
  11. regulaz

    regulaz

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    Jan 4, 2013
    thanks for the links but they are in amps/current

    i was measuring in volts. the current here is very low which can only cause electrostatic shock i.e. high voltage builds over time as person continues to sit on the computer.

    even 3 milliamps can create a mild shock as mentioned in the paper.
     
  12. davenn

    davenn Moderator

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    Sep 5, 2009
    yes BUT ONLY when there is really high voltage "driving" it

    Dave
     
  13. john monks

    john monks

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    Mar 9, 2012
    If this kind of electrical radiation was dangerous I would be dead by now.
    Unless you are concerned with electrical shock the more dangerous radiation
    is X-rays. For this reason you should not be hanging around too long behind
    your monitor. X-rays are usually very low in front of the monitor. But still I feel
    safer in front of LCD displays.
     
  14. regulaz

    regulaz

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    Jan 4, 2013
    sure thing CRTs are not safe as far as xrays are concerned. what about the 1000 millivac on the LCD? and 1500 millivac on the led lcd - that is 3-5 times higher thana CRT. even though it might be too little to bother about in daily use.
     
  15. john monks

    john monks

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    Mar 9, 2012
    Years ago I was given the assignment of writing a safety proceedure for working on electronic circuits. So I started doing my research. I couldn't find any credible evidence that electric fields of a few volts was dangerous. Besides much higher voltages occur in nature even without our electronic devices. If the frequency of an AC field is low not much voltage actually penetrates the human body. If the frequency is a few hundred thousand hertz or higher penetration does take place and the body starts to heat up. With gigahertz the eyes can be damaged by the heating effect. Therefore keeping your eyes from getting to close to a microwave may be in order because the heating may cause cataracs. Getting up into X-rays and gamma rays can cause cancer and death. Thus those wavelengths should be avoided.
    The body itself develops millivolts in the hearts and other muscles.
    Higher voltage can be deadly. Therefore people should know CPR along with other ways of mitigating electrical shock hazards.
    Bottom line, as long as long as a person is healthy, and does not have a pacemaker or other such device, and as one does not come in direct contact with a vew volts there should be no problem.
     
  16. gorgon

    gorgon

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    Jun 6, 2011
    You are definitly NOT talking milliAmpere in these cases, but microAmpere(uA). Since lethal current value is 20-30 milliAmpere(mA) through the body, you'll be dead long before reaching 300mA.
     
  17. regulaz

    regulaz

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    Jan 4, 2013
    im getting 0 microamps but only a voltage. 300 millivac for crt and 1000 millivac for LCD. what exactly is this figure showing? does it show that a rad screen is necessary for both lcd and crt?
     
  18. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    If you fit a rad screen to your LCD monitor, ensure it is earthed to both your lead underwear and your tinfoil hat.
     
  19. davenn

    davenn Moderator

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    Sep 5, 2009
    it is showing random tiny voltages probably most of which is generated by static buildup

    you are worrying about nothing !! get over it and get on with life :)

    Dave
     
  20. regulaz

    regulaz

    9
    0
    Jan 4, 2013
    Thanks for your replies!
     
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