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Re: [Phys-l] glassware needed



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?

Do you feel that THIS device had a bandwidth sufficient to capture a one microsecond current pulse at representative amplitude? :-)

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...

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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Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu

https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l


_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l