Re: [Phys-l] glassware needed

[Bernard Cleyet <bernardcleyet@redshift.com>]

1) obviously it moves, the point is it continues for some time  
(seconds) after the cap. is discharged, furthermore the initial  
amount of movement may be so slight it's not obvious by eye.

1) continued -- I'm too lazy to do the calc., but I suspect a bank of  
caps from disposed film cameras will deliver such a pulse.  I got  
some from Costco.

2) that particular one was inexpensive (whether it was cheap (shoddy)  
is another matter).  My point is w/ some effort, instead of money one  
may obtain "variacs".


On 2009, Jan 05, , at 17:11, Brian Whatcott wrote:

> 1) Interesting that you think a ballistic galvanometer could be  
> motionless
> after the excitation is removed.  ??
>
> Perhaps it would be helpful to recap the principle of the  
> oscillograph.
> A small mirror excited by a moving coil?

and rapidly moving light sensitive paper -- Long Marine lab had such  
a device -- very expensive.  I have part of a similar device.  The  
mirror is actuated by a diaphragm acoustically.  (Phonelescope ptd.  
1912)
> Do you feel that THIS device had a bandwidth sufficient to capture  
> a one microsecond current pulse at representative amplitude?   :-)

Remember I decided you were quite correct, because very overdamped.

> 2) on the topic of cheapness:     I bought a Beckman Fluorimeter  
> for a few dollars on eBay. Does that confirm that these instruments  
> are cheap?
>
> 3) As it happens, I have a moving disk watt-hour meter as well as a  
> cheapy sampling wattmeter.
> No reason why I cannot compare both of them, though I am not up to  
> generating 100 amp 10 microsecond pulses. Pity!
>
> I'll let you know...

bc, can't wait!, and suffers from stream of consciousness writing.

> BrianW
>
> --- On Sun, 1/4/09, Bernard Cleyet <bernardcleyet@redshift.com> wrote:
>
> [rotating disk watt-hour meters...]
> > >  they suffer just the same deficit as the style of meter
> > > that loses narrow power consumption spikes of
> > >   naive experimenters - it's still a bandwidth  issue.
> >
> > You certain about that?
> >
> > I thought, well maybe the inertia of wheel and armature
> > absorbs the
> > pulse and because of the very low source impedance
> > there's no "over
> > shoot", so the  spike will be ignored.  Then I thought
> > of the ballistic galvo. wherein the spike (e.g. discharging cap.)
> > is over  before the armature moves.  OTOH the BG is shunted by a
> > CDRX not way over damped (milliOhms).  To test this at some point
> > I'll drive one of my d 'Arsonval wattmeters (light bulb loaded) w/ an
> > amp driven by a pulse generator, and a filament transformer for Z
> > matching.   O'scope observation, natürlich.
> ....
> > bc can't wait, but already convinced.
> >
> >
> > > Variacs are helpful for maintaining power waveforms -
> > > but they  don't come cheap.
> >
> > p.s. Mark K.  found two and gave me one at the San
> > Francisco City
> > College surplus give away a few weeks ago.  At one time
> > RAFT had a
> > few for a few $$ ea.
> >
> >
> >
> > On 2009, Jan 01, , at 19:42, Brian Whatcott wrote:
> >
> > > Sad to tell, though spinning disk watt-hour meters of
> > the kind used
> > > to meter
> > >   domestic consumption are required to register within
> > 4% at low loads
> > >   and 3% at higher, even inductive loads - they suffer
> > just the same
> > >   deficit as the style of meter that loses narrow
> > power consumption
> > > spikes of
> > >   naive experimenters - it's still a bandwidth
> > issue.
> > > Variacs are helpful for maintaining power waveforms -
> > but they
> > > don't come
> > > cheap.
> > >
> > > BrianW
> > >
> > > At 09:20 PM 1/1/2009, you wrote:
> > > > This allows me to advertise my collection of
> > aquarium heaters for
> > > > very little $. ... Aren't variable auto
> > transformers (Variac) in
> > > > plentiful
> > > > supply? AND  at one time (now too?) watt-hour
> > meters were offered by
> > > > surplus houses.  Since they operate on the
> > principle of one part of
> > > > the motor sensing the potential and the other the
> > current, no problem
> > > > w/ PF.
> > >
> > > ....
> > > Brian Whatcott    Altus OK    Eureka!
> > >
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