Is it normal to have a voltage detector go off in a crawl space when it touches the dirt? any spot in the dirt i used the voltage detector it would go off.
I wouldn’t say normal but it wouldn’t surprise me. Mine will often go off when I bump it into random things.
As far as voltage in the dirt? Nikola Tesla thought he was going to be able to send electricity through the earth and have it come up anywhere. Obviously, that didn’t pan out but he sure did have some ambition.
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Soils are electric current conductors , being usually clay soils, with finer particles and with greater points of contact between them, higher conductors when compared to sandy soils, with coarser particles and therefore with smaller points of contact between them.
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That was a good article JJ…But, I found this amusing. Hopefully someone will develop a human application.
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That depends on the type of tester used and the Voltage.
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If you are using a capacitive coupled “sniffer” you need to read the instructions more thoroughly. These voltage testers come in a variety of sensitivities that may make them more or less useful in different situations. Home Inspectors do not generally test for ‘low voltages,’ so I recommend avoiding the use of testers advertised as detecting low voltages.
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I used a Fluke 2AC
Mike Holt does a great service in explaining stray voltage in the earth in and around buildings and equipment.
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David, Hi!
First of all, What are you trying to do? or What were you doing? when your Voltage Detector went off…!
A ‘sniffer’ is basically closing a circuit (a loop) from the highest voltage point (where you are touching!) to the lowest or the ground. You are holding it, and you provide the ground connection, the means for the current to flow from the point of tension (hot) to ground (Yeap! Your body is the ground conductor, like in all those new touch screens or elevator controls, etc.) However, those sniffers or high voltage detection devices are never in direct contact with the actual hot point, they capture the intensity of electromagnetic fields associated to the presence of a hot point.
There is a capacitor and diodes in the inner circuitry… Depending on the ‘level’ (amount of voltage) present, the electronics give you a green (for absence) and a red for presence (110V or higher). Do not take me to Court, this is a simple explanation of How they work…! Is something like this…!
Knowing what you are trying to do in that crawl space (What are you testing/Touching?) will provide you with a simple/rational explanation of Why is going off?!? If the sniffer is going off (red), you are touching a hot wire.
Pictures illustrating what you are doing always help.
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Proximity sensors such as the 2AC have very high input impedance. Thus, they are susceptible to false triggering. Never rely entirely on any Voltage tester that has an extremely high input impedance.
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What do you consider ‘extremely high’?
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Hey pedro it was just out of curiosity that i wanted to use the voltage detector on the dirt below, thanks
I would like to add to my question, what precautions do home inspectors take to prevent them self’s from be electrocuted in crawl spaces?
That depends on the circumstances, but I consider anything more than one million ohms per Volt to be extremely high. In some instances, a million ohms per Volt is high enough to give false readings.
Most d’Arsonval movement meters are well under a million ohms per Volt. They are typically in the 20-100 kilo-ohm range. You won’t get false readings with a d’Arsonval meter.
Most proximity testers and modern digital VOMs usually have an input impedance of 10 million ohms or more. That, in my opinion, is extremely high and leads to a lot of confusion among apprentice electricians and some (poorly trained) journeymen.
The extremely high input impedance is what makes proximity Voltage testers possible. The trade-off is a lot of false triggering. From a safety perspective, false triggers are more desirable than not triggering in the presence of a Voltage.
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