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It is impossible to online buy a cheap Non-contact Direct Current voltage tester pens.

z234

Dear friends,

I found it is impossible to online buy a cheap Non-contact Direct Current voltage tester pens.

They only sell AC pens.

Does anyone know where to buy cheap Non-contact Direct Current (DC) tester pens , that is not those very expensive Fluke pens?

Thanks for all your great help and May God bless you and your family Two hearts Pray

Parents
  • 0

    I don't really understand the requirement. I can't see how for a "voltage tester" a potential difference would be detected with a pen (e.g. detecting an AA cell!).. presuming the request is to infer a DC flow of current, perhaps by the magnetic field?

    I think a handheld pen method may need the user to frequently null it since if it moves, the weak magnetic field will change too, which doesn't help with a binary present/not present indication.

    You could pack a circuit and little display in a pen. Below is a design that is reasonably accurate compared to commercial devices. However you'd need quite a high current  and be very close to the wire (or alternatively looped into an electromagnet) to get enough of an indication. Formula here: http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html 

    DC current sensors are low-cost (£10 ballpark) and are no-contact, but need the wire looped inside it. You could DIY that to not need the wire to be cut or disconnected, but it sounds like you want a ready-made solution. A ready-made DC current clamp with hinge is about £100, and can be connected to a cheap multimeter.

Reply
  • 0

    I don't really understand the requirement. I can't see how for a "voltage tester" a potential difference would be detected with a pen (e.g. detecting an AA cell!).. presuming the request is to infer a DC flow of current, perhaps by the magnetic field?

    I think a handheld pen method may need the user to frequently null it since if it moves, the weak magnetic field will change too, which doesn't help with a binary present/not present indication.

    You could pack a circuit and little display in a pen. Below is a design that is reasonably accurate compared to commercial devices. However you'd need quite a high current  and be very close to the wire (or alternatively looped into an electromagnet) to get enough of an indication. Formula here: http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html 

    DC current sensors are low-cost (£10 ballpark) and are no-contact, but need the wire looped inside it. You could DIY that to not need the wire to be cut or disconnected, but it sounds like you want a ready-made solution. A ready-made DC current clamp with hinge is about £100, and can be connected to a cheap multimeter.

Children
  • 0 in reply to shabaz

     I also couldn't figure out how one could detect the presence of voltage if it doesn't change and you can't touch it.  Unobtainium.

    As to the pen (on like the third time through), I finally took note of what they didn't say.  They keep to the presence of a magnetic field and all of the listed applications require electromagnetism (aka current flow) to work.  I chuckled a bit when that epiphany hit.  I could see me falling for what I thought to be "inferred functionality".
    It also helped that I got the AC one out and tried to see if I could get that one to respond.  Then I read the spec again.  20Hz minimum response frequency.  Yeah... that ain't gonna happen no matter how much espresso I drink.  I am curious on the current level that it will take to get the pen to respond.  My thought is that it will be above reasonable but we'll find out.

  • 0 in reply to kmikemoo

    Hi Mike,

    I too was looking at a magnetic sensor pen on Amazon just now, and it's very unclear if it is AC or also includes DC.

    What would be neat would be if those magnetic sensing sheets could be placed over a cable and see the difference in field : )

    But that's highly unlikely they are that sensitive : (

    What the OP could want could be a pocket pen-sized gradiometer! : ) i.e. two magnetic sensors, one in the pen tip, one further away in the pen shaft. That would be a fun project to work on, if there was free time (there never is enough of that!).