Re: How to get the output from the light dimmer?

"ooi_yw" <yuwei_1712@xxxxxxxxxxx> writes:

> Hi guys, as far as i know, light dimmer produces harmonic distortions
> to the main supply. In order to check the distorted waveform which
> contains many levels of harmonics, where should I check the output? I
> mean is if i want to use an oscilloscope to capture the image of the
> distorted waveform, where should I put the probe of the oscilloscope.
> Hope you guys can help me. Thanks.

To measure the distortion in the incoming mains voltage waveform,
you need to connect your oscilloscope between the incoming power
live and neutral wires. You can do the connection with a normal
1:10 proble that is safe for mains voltages (need to be
very careful to conenctct exactly right, potentially dangerous) or
more fafely using a differential oscilloscope probe (connect one input
wire to neutral and another to live wire).
If you have completely isolated potable scope (like some fluke
scopemeters and similar) that have just two measurement wires
then wire them to supply voltage.

That gives you information how much voltage waveform distorts.

Another way to measurete harmonics is supply feed is
to take a suitable clamp-on current transformer / probe with
output that you can feed to oscilloscope.
You can see the distorted current waveform on the oscilloscope
screen nicely. The clamp-on current transformer / probe
is just installed over the live wire on the power feed
(can be clamped over insulated phase wire, does not
work with cbles that have all live+neutral on same cable).


Warning: Maing the connections to the mains supply that
feeds the power to dimmer is potentially dangerous and should
be performed only by people who knwo what they are doing
(should be generally left to electrical professionals)
Maing mistakes in connection can lead to damaged equipment,
risk of fire, risk of personal injury and even kill you.
Making mistakes in high current power feed connections
is a receipe for disaster: there is lots or current
(can be many kiloamperes) here available in case of
hort circuit, it can burn cables and cause
an electrical arc flash. Connections should
always made correctly, when system is not energized and
when you apply power back keep the safey distance from
the measurement system (in case something dangerous
happens it will not harm).

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/
.