Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1892-05-22
! AN ELECTRIC METER.
Simple Principle Upon Which the
Amount of Current Is Measured.
ASSISTANCE FOR THE SCULPTOR.
An Underground Conduit Of Non-Conduct-
ing Materials Is Needed.
IMPORTANCE OF LIGHTING IN WAR
WRITTEN FOR THE DIsPArcu.1

WRITTEN FOR THE DISPATCH.1
Many people find it difficult to conceive
how electricity can be measured. The pro
cess Is not hard to comprehend. In an or.
binary Edison meter two compartments VIII
be found, IN the upper of which is thin
piece of German silver running across in q
zigzag line. In the lower compartment,
separated from the upper by bar, which is
part of the castiron construction of the
meter, is spool of copper wire and bottle.
The bottle contains two pieces of zinc,
separated BY piece of rubber. These three
things constitute the meter.
The principle underlying the measure
ment of electricity is that of electro
plating. This is done by means of an cleo
trlc battery, piece of copper being placed
In the battery on the positive pole or wire,
and the object to be plated being placed on
the negative wire. The action of the cur
rent eats away the copper from the po sitivs
wire and deposits it on the article fastened
to the opposite wire. In the electric light
meter two pieces of zinc are used On the
chemical purity of this zinc the accuracy of
the measurement depends
These two pieces of zinc are separated by
rubber and Joined by rubber bolts, so that
they may be near each other and still not
allow OF the inter-passage of the current.
One piece represents the positive pole, the
other the negative. The more electricity
passes through these pieces of zinc the more
zinc will be transferred from the positive to
the negative pole, so that if enough cur
rent be used in course of time all the zinc
will be on one pole. This is is the prinei-
pie of measuring electScity After the
pieces of zinc have been used for some time
one will weigh more than the other, and the
amount of the customers bill IS exactly in
proportion to this difference in weight,
which is arrived at with mathematical ex-
actitude.
But if the bottle were all that was used in
the measurement of the current it would
require q bottle of immense size to measure
the electricity used in the average residence
or store, and the consumption of zinc would
be enormous. Here the piece of German
silver comes in useful This piece of metal
is called a shunt, because it shunts off most
of the electricity and prevents it from going
through the bottle. This strip of metal is
so accurately adjusted that it takes just 999
parts of electricity to one that passes
through the bottle. The current from the
electric light wire, before it goes to the
lamps, passes through the meter; here the
one-thousandth part passes through the
bottle with its pieces OF zinc, the rest being
shunted of through the German silver
The weighing of the zinc plate is very
delicate operation The bottles are col
lected by the agent of the electric light
company, the pieces of zinc are separated,
and the negative piece is carefully washed
and hung up to dry. After this their record
is looked up, and the operator knows to a
millegramme how much each piece of Zinc
weighed before it left the works and was
put in the meter. The zinc is weighed on
most delicate scales, and the difference in
weight is noted down. The decrease in
weight is multiplied by figure known as
the constant, and the result is the bill of
the consumer in dollars and cents. Before
the weighing is begun every door and win
dow is closed, although the operation Is
carried on in an inside room. The least
movement in the air would add several
hundred dollars to some consumers bill