[R-390] Dead horse foaling,. Monkey wrench thrown!

[Roger L Ruszkowski]

Ok ok, for those who don't believe
the math, I did an experiment.

I set up a 24V (i.e. 25.2) transformer
feeding a #93 12V bulb.  Transformer is
on a variac.  Voltmeter on transformer
primary.  Initial voltage: 60V so
the lamp gets 12.  I set up the bulb
in a dark room in front of a photographer's
light meter.  I noted the reading,
put a diode in series with the bulb,
and increased the variac until the
light meter read the same as before.
Answer: 86V.  *NOT* 120V.  And 86V
is approximately 120/sqrt(2).

Regards,
Dave Wise

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Sorry Dave,

Not the same experiment.

The AC volt meter was just reading some value damped by meter
movement mass and springs. Those meter reading are very misleading.

You have a dynamic resistor. It changes resistance with changes in
applied power. What happened to the current when you changed
the voltage that changed the resistance, changed the temperature
that changed the light  that changed the light meter that changed
the voltage meter.

When you installed the diode and read the lamp output level with the light
meter,
was the lamp output 1 /  2 or 1 /  4 or some other output of light level?

Lamp conversion to visible light is not linear.
Filament conversion to heat is not linear.
Either one will dissipate all the energy.
Into which energy band (heat , light , X-ray) who knows.
How much of that energy does our test instrument capture and report?

Even here in your test you expect a uniform average of light to reach
your meter. The lamp make have dark and bright sides. Changing
the power across the lamp may or may not sow the same dark and
bright sides. (hot spots in filament and filament hangers shade the field)
What makes light output to meter reading a real average of light emitted?

I do not know how to make all light emitted be absorbed by the sensor
element.
So how do we ensure that light emitted to light received is linear?
As you changed the light pulse rate from 60 hertz to 30 hertz how
was the pulse filtered by the light meter circuit to hold an average
meter reading.

We think the thermal resistance of a lamp gives a flicker free
output. While the light is better than a florescent lamp, it still has
a flicker and you reduce the flicker rate from 60 to 30 and thus
exaggerate the factor in the test setup.

Install the diode and lamp.
Adjust the power to get a lit lamp and a light meter reading.
remove the diode.
Remeasure the lamp light output.
Is the output twice, four times or some other value more?

This still means nothing. It just lets you infer some thing about
the metering equipment. You can infer any thing.

But if you start on the correct premise, you can infer correct
thing about the response of the meters to real conditions.

Measure, the voltage, the current and the resistance
with the diode and with out the diode.
Compute all permutations of voltage, power, current and resistance.
Show that all equations balance with out error.

The meter reading and math are models of the real world.
If the meters, math and models do not balance, then
its the meters, math and model that is in error, not nature.

Roger.