Re: Measuring impedance of wall socket
- From: Glen Walpert <gwalpert@xxxxxxxxxx>
- Date: Fri, 29 Jul 2005 23:41:24 GMT
On Fri, 29 Jul 2005 15:09:26 +0200, Rene Tschaggelar <none@xxxxxxxx>
wrote:
>Glen Walpert wrote:
>> On Fri, 29 Jul 2005 00:46:43 -0700, "cyrille perron"
>> <cyrille.perron@xxxxxxxxxxxx> wrote:
> >
>> If I were to build one I would use a bank of motor run capacitors for
>> a load, sized for about 10 A at 120 V for measuring typical US 15 Amp
>> wall socket impedance. By applying the load to Line-Neutral and then
>> Line-Ground voltage drop can be measured separately for all 3
>> conductors. Since the change in neutral to ground voltage provides
>> the voltage drop on the neutral or ground (whichever is carrying
>> current), the rest of the total voltage drop is due to the Line (Hot)
>> conductor impedance. Any other means of applying a load and measuring
>> voltage drop at a known current can acomplish the same thing.
>
>The impedance always belongs to a frequency. You're
>measuring at line frequency here.
>
>Rene
and
On Fri, 29 Jul 2005 14:39:28 +0100, Paul Burke <paul@xxxxxxxxxx>
wrote:
>Glen Walpert wrote:
>
>> By applying the load to Line-Neutral and then
>> Line-Ground voltage drop can be measured separately for all 3
>> conductors.
>
>Most modern UK installations have an RCD on the socket rings, and this
>test would send it flying.
>
>Paul Burke
Both good points. If you build a uP controlled tester with a couple
of fast simultaneous sampling A/D converters for voltage and current,
and apply the load close to midpoint between voltage zero crossings
(at a voltage peak) with a fast solid state switch, you could probably
get enough samples to estimate impedance vs freq over a reasonable
range before the RCD (GFI in the US) trips. But the short sample
period would defeat part of the purpose of the high current test load,
which is to heat up any high resistance connections which will often
change resistance noticably in under a minute of high current testing,
at least from what I remember of an article on line impedance testing
I read in EC&M a decade or two ago, probably written by an impedance
tester salesman of course. You could still do the sustained high load
test on Line-Neutral of course. And while you were at it you could
put a separately switched low current load to ground in to test the
RCD.
This may be more than the OP wanted to know; the toaster with
multimeter approach should work fine unless you want to do a lot of
testing or investigate power line comms or lightning surge control.
.
- References:
- Measuring impedance of wall socket
- From: cyrille perron
- Re: Measuring impedance of wall socket
- From: Glen Walpert
- Re: Measuring impedance of wall socket
- From: Rene Tschaggelar
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