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Thread: Why do I have voltage when switch is off?

  1. #16
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by DonL View Post
    Hello all,
    The comment ;
    "Case in point, although an eight dollar analog meter from an electronics store might just blow up in your hand if used incorrectly.
    Although the meter is fused it is not rated for flash over."
    First off You should not be holding a meter in your hand when taking measurements, Bad Idea even if it is called a hand-held meter.
    and there are going to be cases where there is no other choice but to hold the meter while testing such as the use of an ammeter.
    Quote Originally Posted by DonL View Post
    Flash over is normally a mater of lead spacing, and good meter leads.
    or the blowing of a SFE fuse in the meter where arcing occurs between the blown portions of the fuse
    Quote Originally Posted by DonL View Post
    Any Cat II rated meter will be safe for Household use. But I make a habit of not holding one in my hand while measuring.
    That may not be in any book, Just command sense.
    In most cases a Cat II meter would be alright for testing but the closer you are to the supplying transformer the higher the Cat rating needs to be. It is possible to have more available calories per square centimeter on a single phase 240 volt panel than on a 480 volt three phase panel.

    Quote Originally Posted by DonL View Post
    That will "ensuring that I am not wasting time laying around recouping from an accident"
    If You have a problem with putting your meter on the wrong range or setting , It is best not to be using it.
    Having a safe procedure that is followed time and time again will ensure that the wrong setting is not used. Just simply picking up the meter and using it creates bad habits and bad habits result in accidents.

    Quote Originally Posted by DonL View Post
    All Randyj needs is a Neon Bulb Built into an Electricians Screwdriver. Works Good Last a Long Time.
    I know these are used daily but I highly recommend they not be used. Ever be around one during an arc and you will throw yours away.

  2. #17
    Jack of all trades DonL's Avatar
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    Hello JW and all.

    The use of a ammeter on AC and holding it in your hand is different than Connecting it into the circuit.
    You are just reading the Current going threw the wire. Unless you are reading DC current, you need no direct connection.

    Cat II is rated at 600 Volt. If You have more than that in your house, Then the Transformer Is on the wrong tap, Wont come close to 600.

    The Fuse on the meter is to protect the meter for operator error, Not for the users protection, Just protects the meter.

    Using the Proper rated leads is more protection than any fuse will proved. Fuses blow slower than flesh.

    JW, Have You ever heard of keeping 1 hand in your pocket ?

    If you work on 3 phase systems then of coarse you need at least a CAT III meter.

    CAT II is fine for working around the house, and is considered Low voltage. It depends what you compare it to.

    You mix Apples and Oranges when you say a ammeter is the same as a voltmeter, as far as safe use.
    Same applies to hand held Non Contact Devices, Thay are safer, but not as accurate.

    Direct connection to a unknown voltage is always a risk.

    I guess I am not hearing where you are coming from.

    We are talking about working around the house, not bench or factory work. Single Phase System.
    Unless a factory is your home.

    A neon Bulb is better that the touch test. The old timers used the touch test, But I do not recommend it.

    I will not throw my Neon tester away, The screwdriver still works, lol.


    Enjoy your day.


    DonL
    Last edited by DonL; 04-27-2011 at 11:34 AM. Reason: OP Error

  3. #18
    Electrical Contractor/Instructor jwelectric's Avatar
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    It is not the voltage rating that is the problem. The category rating on meters is the ability of the meter to stand up to transient voltages from such things as surges from lightning, grid switching, large capacitors and so forth.

    As I have said a category II or III in most cases will be fine for checking voltages around most residential branch circuits, but the closer you get to the supply source the more likely to run into voltages transients and the higher the category rating of meter will need to be used.

    Voltage transients are a very common occurrence in AC utility furnished power.

    Checking the amperage of a conductor is just as dangerous if not more so than taking a voltage reading. When taking an amperage reading most people get a false sense of safety due to the fact that they are not coming in contact with a live terminal such as doing a voltage reading.

    During an amperage test the meter can be subject to more voltage than doing a voltage reading simply due to the makeup of the meter. The jaw of an amp probe is a simple transformer winding that opens and the closes around the conductor. It is again opened to remove. In both cases bare metal is exposed to the live circuit. Arc flashes have occurred during amp readings.


    The fuse internal to a meter is not a rated fuse. Most are simple AGC/SFE type fuses and these will arc over if they get started. The ionization of the air around the fuse will conduct current. This I have witnessed myself. Having a DVM set for an amperage or resistance test and touching the leads to a live circuit can result in a very enlighten experience and with shocking results. Did you catch the pun in that sentence?

    Make it a practice to always be checking the setting of you meter to remain safe while using the meter is not bad advice no matter the person making the statement.
    Knowing the limitations of a meter is good advice no matter who is giving it.
    Understanding the dangers involved with the use and maintenance of electrical circuits is good advice for anyone to listen too. Now you either agree with this or you disagree, which is it?

  4. #19
    Jack of all trades DonL's Avatar
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    Hello all.

    To answer JW;
    "Understanding the dangers involved with the use and maintenance of electrical circuits is good advice for anyone to listen too. Now you either agree with this or you disagree, which is it? "

    I agree with You for the most part.

    The Amp Meter that own and use most has no Exposed Metal, and is Double Insulated.
    I very rarely check UN-insulated wires, other than checking for current on the ground wire.

    Like I said before, If a person does not no what they are doing, They should not be using any electrical testers.

    People get hurt every day sticking a knife into a toaster.

    How many people do you think disconnect their car battery before changing their motor oil ?
    Not many, even if the owners manual says to do so. (I sure don't, waste of my time)

    It is hard to protect against stupitdy.

    Have a great day.

    DonL

  5. #20
    Jack of all trades DonL's Avatar
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    Where did You go Randyj ?

    Sorry Your Thread got blown out, but you stir and run, lol.

    Get back in an tell us your outcome. I know You are over there laughing.

    Tell us about your shocking experience.

    Sometimes the best meters give false readings, if there is stray stuff flying around.

    Just think about all the RF bombarding you at this very moment.
    You can Rectify the RF in the air using PIN Diodes and charge batteries. I kid You not.

    Have a Great day.


    DonL

    "Books tell how it should be, Experience tells how it is"

    P.S. Make sure to use your PPE when talking on your cell phone.
    Last edited by DonL; 04-28-2011 at 02:27 PM. Reason: P.S.

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