Curt Welch wrote:
Brian Lawson wrote:
On Mon, 30 Jun 2008 20:17:24 -0400, E Z Peaces
wrote:

Brian Lawson wrote:
On Mon, 30 Jun 2008 09:29:33 -0400, E Z Peaces
wrote:

Smaug Ichorfang wrote:
The more I look at 1338, I wonder if it is indeed aa metal-foil
electroscope. Typically these have very thin pieces of metal foil
suspended from a central conductor. The center piece in this looks
way too thick to be an electroscope. Does the center piece move;
can it pivot from side to side? Are the two terminals on the sides
adjustable? Is it possible this is a tilt switch of some sort?

How about a line frequency monitor from a time when automated
equipment to keep a generator on frequency was not reliable.

SNIP

Naw. Prior to the 40's, flyball governors were used to do that.

A flyball governor can keep a motor running at a nearly constant speed,
but synchronous clocks, invented in 1916, require precise speed control
If the generator is 1% slow (59.4 Hz), clocks will lose about 15 minutes
a day.

Doesn't that point to the need for a tuning fork to monitor the
governor? A meter could provide the necessary information, but a man
might notice the absence of a hum before he would happen to look at the
meter.

The way to regulate it accurately is to drive a clock with the current and
compare the time of the clock to an accurate time source (like the sun).

For the clock problem, the short term frequency is not as important as the
long term average frequency. So when the clock is running behind, you just
speed up the system a bit until it catches up. The fact that the frequency
is only accurate to 5% is not important if you can keep the long term
average accurate which is easy enough to do just by driving a synchronous
clock from the power.

I was once told that the above is what power companies actually did (at
some point in history). Don't have a clue if it's true however.

Here's Henry Warren's patent showing the state of the art in the early
1920s: 1502494.

The device would count up the difference in rotations between a pendulum
clock mechanism and a synchronous electric clock motor. I think it
registered in seconds. The patent shows the generator engine throttled
by a flywheel governor in parallel with a manual valve. The governor
was intended to keep the speed nearly constant, and the attendant would
make adjustments with the manual valve.

Here's a Warren patent showing the state of the art in 1916: 1283431.

He says a large power station normally kept the frequency between 59 and
61 cycles, and a larger deviation shouldn't last more than 20 seconds.

I think it would take an audio signal(in a quiet office in a brick
station) to ensure such a quick response. For example, the price of my
neighbor's favorite stock scrolls across the screen every few minutes,
but he misses it almost every time because he's not paying attention
during the few seconds it's visible. If the sound stopped, that would
catch his attention immediately.

The attendant would need an indicator to adjust the valve when the clock
device showed the generator had lost or gained time. He couldn't just
open the valve a quarter of a turn, for example, because the engine's
response would depend on the load on the generator. Perhaps tuning by
ear, listening to the hum of a mechanical resonator, was more reliable
than a visual frequency indicator.