I put a 75w equivalent CFL on a scope with a current probe, looking at
the wave form.
This is what it looks like
Those spikes are almost 2 amps so this might average 33w but it is not
that simple. I assume this is also a very reactive load so if you
opened a relay at or near peak, it could get pretty ugly
On Thu, 26 Nov 2015 08:06:35 -0800 (PST), bob_villain
I have had it since AOL started, long before anyone even knew what the
internet was. (Prodigy before that)
Right now I like it for my public Email address because I run AOL7 and
those nasty script based attacks simply pop up a gray error box.
On Thu, 26 Nov 2015 13:29:38 -0500, "Ralph Mowery"
I have a clamp on accessory for my Fluke meter that works as well but
you can't really trust the calibration as much, although the scope has
not been calibrated since the Clinton administration. It used to be on
a regular schedule when we were ISO 2000/1.
I got it as a present when I retired, along with my 453 Tek and a
bunch of other test equipment that nobody who stayed, knew how to use.
One of my favorites is the Dranitz 626 line monitor. You don't need it
much but when you do, there is not much else that will work.
Should be pretty obvious -- current repeats with a periodicity that
tracks (rectified) line frequency. So, 8.3ms between repetitions...
You're not concerned with the actuation/release time (except if you
try to synchronize it with a certain point on the waveform (e.g., to
deliberately avoid these spikes which are roughly coincident with voltage
peak). You're more concerned with how long the contacts bounce
as they make/break -- especially when opening the connection
(cuz current is flowing and will want to maintain an arc across the
widening gap --> contacts melt)
That was a great 'scope! I lugged one around the country at my first
job. Wouldn't enjoy doing that nowadays, though! :<
Presently using a rescued TDS754D -- for the few occasions when I actually
need a 'scope.
On 11/25/2015 11:51 PM, email@example.com wrote:
I suspect they are roughly coincident with the peak (slightly leading)
of the voltage waveform. So, apparent power is much higher (2A @ ~80+V?)
The problem with relay drives is you can't readily predict how
long it will take for the contacts to open. So, you can't
realistically try to open it near a zero crossing (or, ANYWHERE
that is "away from" the peak of the cycle and the peak current
Likewise, unless it's a Hg-wetted relay, you can't tell how long
the contacts will *bounce* when making.
And, of course, if you're making consumer kit, you're usually quick
to trade off *any* sorts of real "specifications" for a few
Do you have access to a DSO? If so, you might try catching the
turn-on transient to see what a discharged primary cap looks
like to the line!
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