Voltage detectors how work?
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jimwalker
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Re: Voltage detectors how work?
induction
induction
Re: Voltage detectors how work?
Induction would require a current to flow in the circuit being tested. But I don't know the correct answer.
I think Physis is probably onto something. But capactance to where? It seems like that would require a grounded system, and maybe uses the body of the person holding it to get capactiance to ground? I think we need to find a complete loop for current to flow around to say we know how it works.
Steve
Induction would require a current to flow in the circuit being tested. But I don't know the correct answer.
I think Physis is probably onto something. But capactance to where? It seems like that would require a grounded system, and maybe uses the body of the person holding it to get capactiance to ground? I think we need to find a complete loop for current to flow around to say we know how it works.
Steve
zog
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Re: Voltage detectors how work?
There may not be a magnetic field but there is an electric field, thats what is being sensed
There may not be a magnetic field but there is an electric field, thats what is being sensed
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- Semi-Retired Electrical Engineer
Re: Voltage detectors how work?
Saying "capacitance" and saying "electric field" is saying the same thing. A capacitor stores energy in the form of an electric field. A voltage source imposes an electric field throughout the complete path (if there is one), and that is what causes current to flow. If there is no complete path (i.e., no current flowing), then the electric field will be imposed upon the space surrounding the conductors. If the only thing blocking the complete path is a set of contacts on a single switch, then the greatest concentration of the electric field will be in the space between the contacts. But it will exist, albeit with a lesser intensity, throughout the circuit.
To detect the presence of an electric field, all you need is a charged object, and the ability to measure any force imposed upon it, or the ability to measure the motion of the charge (i.e., current) in response to that force. Any charge that is in the presence of an electric field will feel a force. The force will be either in the direction of the source of the field or in the opposite direction, depending on the nature of the charge (i.e., positive or negative).
I don't know how these things work. But I would bet that the fundamental method of detection involves electronic components, as opposed to electrical components. That's as far as I can take it.
Saying "capacitance" and saying "electric field" is saying the same thing. A capacitor stores energy in the form of an electric field. A voltage source imposes an electric field throughout the complete path (if there is one), and that is what causes current to flow. If there is no complete path (i.e., no current flowing), then the electric field will be imposed upon the space surrounding the conductors. If the only thing blocking the complete path is a set of contacts on a single switch, then the greatest concentration of the electric field will be in the space between the contacts. But it will exist, albeit with a lesser intensity, throughout the circuit.
To detect the presence of an electric field, all you need is a charged object, and the ability to measure any force imposed upon it, or the ability to measure the motion of the charge (i.e., current) in response to that force. Any charge that is in the presence of an electric field will feel a force. The force will be either in the direction of the source of the field or in the opposite direction, depending on the nature of the charge (i.e., positive or negative).
I don't know how these things work. But I would bet that the fundamental method of detection involves electronic components, as opposed to electrical components. That's as far as I can take it.
macmikeman
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Re: Voltage detectors how work?
If my memory is serving me correctly, it is working from capacitance. You are part of the circuit while you are holding the volt sensor in your hand.
If my memory is serving me correctly, it is working from capacitance. You are part of the circuit while you are holding the volt sensor in your hand.
lauraj
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- Portland, Oregon
Re: Voltage detectors how work?
Fluke actually has a great explaination of how these work on there website somewhere. I'll have to do some searching to find it. It does work by capacitance, which is interesting because it relies on a ground reference through your body. I believe this means that they are not guaranteed to work if you are on a ladder, although I have yet to find a time that it has not worked in that situation.
Fluke actually has a great explaination of how these work on there website somewhere. I'll have to do some searching to find it. It does work by capacitance, which is interesting because it relies on a ground reference through your body. I believe this means that they are not guaranteed to work if you are on a ladder, although I have yet to find a time that it has not worked in that situation.
lauraj
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- Portland, Oregon
Re: Voltage detectors how work?
Here is the fluke pdf: http://www.cjatc.org/Knowledge_Base/Tick_Tracers/VoltAlert.PDF
ECM also has a great article: http://www.ecmweb.com/mag/electric_know_capacitive_voltage/
Here is the fluke pdf: http://www.cjatc.org/Knowledge_Base/Tick_Tracers/VoltAlert.PDF
ECM also has a great article: http://www.ecmweb.com/mag/electric_know_capacitive_voltage/
lauraj
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- Portland, Oregon
Re: Voltage detectors how work?
But you do need a person sometimes. If I put my tick tracer up close to a lamp base, it will glow as long as I am holding it. As soon as I let go of it (lay it down next to the lamp), it will stop glowing. It needs me to complete the path.
But you do need a person sometimes. If I put my tick tracer up close to a lamp base, it will glow as long as I am holding it. As soon as I let go of it (lay it down next to the lamp), it will stop glowing. It needs me to complete the path.
macmikeman
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Re: Voltage detectors how work?
I have a few of the orange ones and they do need a person in order to work since you have to squeeze the clip while using it. My Greenlee one works while I am not holding it if I just stick it in the hot side of a receptacle outlet and leave it in the on position. So now that I think about it my previous post was incorrect. The Greenlee one is good for finding a breaker if you are within earshot of the panel.
I have a few of the orange ones and they do need a person in order to work since you have to squeeze the clip while using it. My Greenlee one works while I am not holding it if I just stick it in the hot side of a receptacle outlet and leave it in the on position. So now that I think about it my previous post was incorrect. The Greenlee one is good for finding a breaker if you are within earshot of the panel.
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- Lockport, IL
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- Semi-Retired Electrical Engineer
Re: Voltage detectors how work?
If a tick tracer is left on a table, and there is no person nearby to discern any glowing or ticking sound, is there voltage?
zog
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- Charlotte, NC
Re: Voltage detectors how work?
OK then (BTW Nice links Laura), how does a tic tracer work when mounted on the end of a hot stick?
OK then (BTW Nice links Laura), how does a tic tracer work when mounted on the end of a hot stick?
physis
Senior Member
Re: Voltage detectors how work?
There's a semicondtor device, a hall effect switch or transducer that detects magnetic fields. I'm not aware of one that detects electric fields (electric field is more corrector than my use of capacitance Zog ) but that doesn't mean there's not such a thing. It's been around ten years since my semiconductors era, there might be new stuff out.
There's a semicondtor device, a hall effect switch or transducer that detects magnetic fields. I'm not aware of one that detects electric fields (electric field is more corrector than my use of capacitance Zog
) but that doesn't mean there's not such a thing. It's been around ten years since my semiconductors era, there might be new stuff out.lauraj
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- Portland, Oregon
Re: Voltage detectors how work?
So I taped my Fluke VoltAlert to the end of a hot stick, stuck it in the receptacle and it glowed just as bright as ever. Next to the tv cord that is up in the air, same thing.
[ January 06, 2006, 06:13 PM: Message edited by: lauraj ]
So I taped my Fluke VoltAlert to the end of a hot stick, stuck it in the receptacle and it glowed just as bright as ever. Next to the tv cord that is up in the air, same thing.
[ January 06, 2006, 06:13 PM: Message edited by: lauraj ]
Re: Voltage detectors how work?
Sam, Hall effect bridges are used to sense fairly strong magnetic fields. Your auto engine may have several of them. The distributor is a prime example. Tic tracers comprise a capacitive voltage divider along with a hi-Z comparator. There is capacitance between the body of the unit and ground, and this forms the divider without a human body in between. So, some of these units may work well, perhaps better, without a sweaty hand around them.Originally posted by physis:
There's a semicondtor device, a hall effect switch or transducer that detects magnetic fields. I'm not aware of one that detects electric fields (electric field is more corrector than my use of capacitance Zog
Re: Voltage detectors how work?
Line1--C1--R0--C2--Ground
Now connect an opamp across R0.
As you move the probe nearer and nearer to Line1, C1 becomes larger and larger. At some point enough voltage will be developed across R0 to create a 60Hz square wave at the opamp output.
It is more complicated than this I am sure, but this is the fundamental idea.
Sam, I will write a schematic for you in English:
Line1--C1--R0--C2--Ground
Now connect an opamp across R0.
As you move the probe nearer and nearer to Line1, C1 becomes larger and larger. At some point enough voltage will be developed across R0 to create a 60Hz square wave at the opamp output.
It is more complicated than this I am sure, but this is the fundamental idea.
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