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Drew
18-01-2013, 10:10 AM
If a volt stick senses the
magnetic field of a wire why doesnt it pick up the magnetic field of a 0volt neutral wire that is carrying current. As it only seems to pick up the live 240 volt. I thought if their is current flowing even at 0volt we would have a magnetic field which the volt stick would sense?

HVACRsaurus
18-01-2013, 10:35 AM
Ever tried using a volt stick on a solenoid or a permanent magnet? It don't work.. I suspect they are "tuned" to the electro magnetic field of 240V AC. Along the neutral, yes the current may be flowing, but it doesn't have the same sine wave style of emf. Think of a typical drawing showing 240 VAC sine wave, the phase is the wave & the neutral is the straight line or axis, which does not have rise & fall in voltage.

Drew
18-01-2013, 10:43 AM
So it's not just the fact of the mag field (which the neutral would have), but the distinctive 240volt signature of the live. Thanks again mate.now I can watch the rest of caddy shack.

NoNickName
18-01-2013, 11:38 AM
A neutral wire doesn't necessarily have 0 volt to ground. It depends on the impedance of ground loop.

The Viking
18-01-2013, 06:49 PM
Try another test with your Voltstick, insert the rear half of it in to a lagging tube so you can hold it without touching it...

Will it still work?

:cool:

.

install monkey
18-01-2013, 07:49 PM
volt sticks only detect over 150v

Voltage sensing ranges





Nominally, 90 V AC to 1000 V AC or 200 V AC to 1000 V AC depending on model, 45 Hz to 405 Hz; also a 20 V to 90 V control circuit model

Drew
18-01-2013, 11:36 PM
Thanks all.

Frikkie
03-02-2013, 12:04 AM
Throw the volt stick (and the neon screwdriver) away, there's lots of instances where these things will give you a false or ambiguous indication. Use an ammeter to measure current flow and a voltmeter to measure voltage you will live a much longer and happier life.

install monkey
03-02-2013, 12:17 AM
also fused test leads are a must, and also a 2nd meter as a means of prooving a circuit is isolated

Drew
03-02-2013, 03:58 AM
A volt stick has its place. I agree I wouldn't risk my life on it and always check with testers, but as an initial fault finding tool it's great. Also works well with door heaters and drain heaters (the ones without the wire braiding) to find a broken live. In control circuits I have used it to locate broken neutrals by following the control circuit,through the load to the break. It's small and fits in my tool belt. I reckon pay for a good one ( as all your testers should be) and check with a voltmeter. I've used them for 25years. So far so good. Hope you enjoy the super 15 rugby Frikkie. Cheers Andrew ( ex kaapie)

hvacrmedic
03-02-2013, 02:09 PM
A volt stick doesn't sense current or magnetic fields, it senses electrical potential (voltage). AC voltage in particular.

Drew
03-02-2013, 07:52 PM
Any idea on how it picks it up?

chilliwilly
03-02-2013, 09:09 PM
It uses an antenna in the nose of the stick to pick up the flux like a radio receiver and amplifies it to cause the stick to light up and bleep, then maybe uses an electro static effect with you being the other plate of the capacitor to measure the potential difference. Or uses the reference of the 0 volts on the negative battery terminal and compares it with the potential of the voltage that its picking up. Probably why it doesn't pick up a neutral, as its the same potential as the battery negative terminal, or with you being in touch with and being the same potential as earth .

The first one that I got and still have somewhere was a Robin OMD10 that could be adjusted for sensitivity allowing for it to pin point voltage within a bunch of cables. Being curious one day I noticed that if I jumped up whilst it was picking up a signal, it would stop then start bleeping again when I landed. The Fluke that I use now still bleeps if I jump, maybe its set up using the battery terminal as a reference point.

Frikkie
08-02-2013, 05:53 PM
......I noticed that if I jumped up whilst it was picking up a signal, it would stop then start bleeping again when I landed. The Fluke that I use now still bleeps if I jump, maybe its set up using the battery terminal as a reference point.

They use you (the person holding it) as a reference via capacitive coupling or by direct contact in the case of a neon screwdriver. The trouble is if you're on insulated flooring or even up a pair of insulated stepladders they might not work. They're also very prone to magnetic and radio interference, possibly cellular phones could also cause false readings. My advice still stands, throw them away, they're skittish and unreliable and sooner or later you'll get a confusing test result that could end with you getting a shock.


Hope you enjoy the super 15 rugby Frikkie. Cheers Andrew ( ex kaapie)
I went to watch the cricket test with my daughter the other day, the poor Kiwis were all out for under 50. A great day for the locals :)