I purchase Lap pen tester, was inserting the batteries and testing, the pen starts bleeping but there was nothing next to it apart from laptop and iphone both charging. The bleep was caused from the iphone even from 6 inches away from the cable. The pen is supposed to detect AC voltage from 50-1000V. An iphone charger is 5 or 12V DC, why is the pen tester detecting?
Pen tester detects voltage from iphone charge
- Thread starter yartin
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Exactly; doing the same beeping over brick wall when there's nothing; there must be an explanation!
Basically reliability is 50% at best, If beeps means nothing but seems fine to rely on if doesn't beep when you touch a cable.
Sometimes the blame is on magnetic field when there are other cables nearby but doesn't make sense when beeps 6" away from a usb cable or touching brick wall.
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My clamp on tester will beep with lap top, since 4 levels one can quickly work out what is making it bleep and the bars show.
The non contact volts is a good test before removing a FCU to see if still live, one can normally see the difference. Before and after isolating so still a good tool.
The non contact volts is a good test before removing a FCU to see if still live, one can normally see the difference. Before and after isolating so still a good tool.
Power supply leakage.
I can make those things light up by rubbing them on my arm
Is that a proper Apple charger purchased from Apple?
Or some knockoff piece of junk from some other source?
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There will be some AC present on the output of a SMPS power supply.
Especially if it’s a garbage one.
Especially if it’s a garbage one.
Between the two wires from the charger there is a potential diffference ( a voltage ) of 5 or 12 volt
The internal circuitry in the charge floats at the mid point of the Live and Neutral as there is no earth connection. There is some small capacitive coupling between this mains circuitry and the extra low voltage circuitry that controls the output voltage. Most of this coupling is between the windings in the isolation transformer. If the charger output is not connected to anything then this capacitive coupling will pull the output towards the mains midpoint ( circa 115 Volts above ground ), This 115 Volt may be enough to trigger a pen sensor. It is also enough to create a tingle in a person who touches the output of the charger but the current taken by the person being tingled is limited by the size of the capacitive coupling in the charger,
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Personally I have very little experience with VF testers, so enough to have formed my own opinion.
A couple of weeks ago I worked on a replacement 2G2W switch (both 2W top & bottom of stairs) with 4 red/black T&E, using a LED screwdriver and the customer said he used to have one but threw it away because someone on 'ebay' said how useless and dangerous they are and was going to get a VF tester as the video recommended, but had not got around to it.
A few moments later he'd found the 'youtube' video to show me... About 3 seconds in I immediately recognised it and explained I was using a LED version but suggested the video gave a very biased view, especially as the comparison between a neon screwdriver and the volt free tester gave exactly the same results. For his benefit I then changed to a neon screwdriver and explained my tests to identify the 2 lives and one strapper as he made himself useful by noting the results.
A couple of weeks ago I worked on a replacement 2G2W switch (both 2W top & bottom of stairs) with 4 red/black T&E, using a LED screwdriver and the customer said he used to have one but threw it away because someone on 'ebay' said how useless and dangerous they are and was going to get a VF tester as the video recommended, but had not got around to it.
A few moments later he'd found the 'youtube' video to show me... About 3 seconds in I immediately recognised it and explained I was using a LED version but suggested the video gave a very biased view, especially as the comparison between a neon screwdriver and the volt free tester gave exactly the same results. For his benefit I then changed to a neon screwdriver and explained my tests to identify the 2 lives and one strapper as he made himself useful by noting the results.
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I was in the 70's moving a socket, house unoccupied so simply turned off main isolator, turned out supplied from next door, using a neon screwdriver saved me from a nasty shock.
The whole point is any device which gives one a warning is good, be it a borrowed neutral or stealing electric.
But to show dead we have a procedure, to suggest we bypass this would be wrong.
The whole point is any device which gives one a warning is good, be it a borrowed neutral or stealing electric.
But to show dead we have a procedure, to suggest we bypass this would be wrong.
Sorry I felt I had to alter you comment.
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Using a tablet, keeps changing words with its spell check.
If I am to remove a scoket, easy to show I have opened correct RCBO by plugging something in, the loop impedance tester for example. But with a FCU the non contact tester allows us to test we have the correct RCBO before we remove screws and can use a hard wired tester.
Since the non contact volts is part of my clamp on multimeter may as well use it. But as to buying a NCV tester, only ever got one with a magnetic detector built in, to test solinodes and the like.
I watched people testing them by rubbing on clothing, and know the Reed switch is easy to damage, since the new ones have a graduated reading mine in 4 stages I assume no longer use a read switch?
But seen them fail so often I would never rely on them. I may use a multimeter to test for dead, which one should not really use any tester which can be switched off or have discharged batteries, but I don't carry both. An as to proving units, tend to test on another socket, for a proving unit to be any good it must show the tester will work with 50 volt, and so many used 400 volt, so next to useless. May as well use my jump start unit with a 300 watt inverter and 230 outlet, unless the proving unit steps through the voltages it is not worth having.
But I have used those daft units which give out 400 volt, as it was a dismissal offence to be caught without one.
If I am to remove a scoket, easy to show I have opened correct RCBO by plugging something in, the loop impedance tester for example. But with a FCU the non contact tester allows us to test we have the correct RCBO before we remove screws and can use a hard wired tester.
Since the non contact volts is part of my clamp on multimeter may as well use it. But as to buying a NCV tester, only ever got one with a magnetic detector built in, to test solinodes and the like.
I watched people testing them by rubbing on clothing, and know the Reed switch is easy to damage, since the new ones have a graduated reading mine in 4 stages I assume no longer use a read switch?
But seen them fail so often I would never rely on them. I may use a multimeter to test for dead, which one should not really use any tester which can be switched off or have discharged batteries, but I don't carry both. An as to proving units, tend to test on another socket, for a proving unit to be any good it must show the tester will work with 50 volt, and so many used 400 volt, so next to useless. May as well use my jump start unit with a 300 watt inverter and 230 outlet, unless the proving unit steps through the voltages it is not worth having.
But I have used those daft units which give out 400 volt, as it was a dismissal offence to be caught without one.
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