Improvements in Self Recording Electric Meters.
Year: 1893

page_text: Date of Application, 11th Jan., 1893
Complete Specification Left, 11th Oct., 1893-Accepted, 11th Jan., 1894
PROVISIONAL SPECIFICATION.
Improvements in Self Recording Electric Meters.
ARTHUR WRIGHT 26 Park Crescent Brighton Electrical Engineer do hereby
declare the nature of this invention to be as follows:-
:―
A self recording ammeter or voltmeter, consisting of a combination of a
differential thermometer, heating coils & recording indexes.
One of the thermometer's bulbs or heat receptacles is heated to a greater or
lesser extent by the electric current to be measured, passing through a resistance
in its proximity & through the medium of a suitable liquid, non-returning indexes
are moved into position showing on a scale the maximum difference or variation of
temperature that has occurred between the two bulbs since the indexes were last
set, this difference being only caused by the electric current indicates the maximum
current that has passed through the apparatus in a given time or the greatest
variation that has occurred.
The resetting of the indexes can be done by making them of a magnetic material,
as is done in ordinary maximum & minimum registering thermometers, and putting
them, back to zero by means of a small magnet.
When the instrument is used for ascertaining the maximum current taken by a
consumer from electricity supply mains, I sometimes provide a scale the position of
the index on which, may indicate the maximum current in ampères or the greatest
number of standard lamps that have been used; or in cases where a reduction in
price is made after the maximum demand has been used more than a certain
number of hours, the scale can indicate directly the quantity of electrical energy
that must be consumed before the reduction in price takes place.
When it is required to record the maximum variation of current or electric
pressure, two non returning indexes are used, one recording the maximum amount
of the current passed & the other the minimum so that the difference between the
two indexes will indicate the greatest variation that has taken place in a given
time in the quantity or the pressure of the electric current.
Dated this 10th day of January 1893.
COMPLETE SPECIFICATION.
Improvements in Self Recording Electric Meters.
ARTHUR WRIGHT 26 Park Crescent Brighton Electrical Engineer, do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
My invention has for its object the construction of self recording electric meters
which can be used for ascertaining or recording the maximum or minimum current
or the extreme variation in the current that has passed through the instrument in a
given time, and the use of a maximum electric current recording meter when
furnished with a suitable scale as a means of ascertaining, for purposes of charging
for supply of current, what quantity must be consumed to equal a use for a given
number of hours of the maximum current that has been recorded.
My invention in so far as it relates to the apparatus, consists in the employment
of a combination of a differential thermometer, provided with means for recording

page_text: or determining the greatest variation that has occurred in a given time of the temper-
ature between the two thermometer bulbs or heat receptacles and an electric heating
coil through which the current to be recorded is made to pass, and which coil heats
to a greater or less degree one of the thermometer bulbs or heat receptacles. Having
now described my invention in general terms so as to define its scope I shall in
order that it may be easily understood proceed to explain by reference to the
drawings of some of the forms in which it may be constructed or carried into
effect.
Figure 1 represents a differential air thermometer with two hermetically sealed
tubes A & B, connected together by a glass tube C, sufficiently small in section to
retain a column of a suitable liquid D, preferably sulphuric acid or other liquid
having low vapour tension, separating the two bulbs and in such a manner as to
divide the two bodies of air or other suitable gas contained in A & B respectively;
the position of D in the tube CC will then obviously depend on the relative
temperatures of the air contained in the two bulbs A & B.
The bulb A is placed in proximity to, contains, or is surrounded by a resistance
coil or strip R through which the whole or part of the current to be recorded is
made to pass.
The strip R having an appreciable resistance becomes heated to a greater or
less extent on a current of electricity passing through it; this heat causes the
contained air or gas in the bulb A to expand and thereby force the liquid D
along the tube towards B, compressing the air contained therein until the pressure
in the two bulbs again equal and the bulb A has reached a steady temperature
above B.
For the purpose of recording the extreme movements of the liquid column D,
I insert in the tube CC suitable recording indexes E & F which may be similar
to those used in maximum and minimum thermometers, which indicates against an
adjoining scale S the extreme extent of the movements of the liquid column.
These indexes may contain magnetic substances for the purposes of being reset by
a magnet placed outside the tube, or the tube may be tilted or shaken so as to
bring the indexes back to the end face of the column of liquid D for the purpose
of re-setting the instrument.
It will be seen from the above description that the position of the indexes E
& F at any time will depend respectively on the maximum and minimum currents
that have passed through the resistance R since the instrument was last re-set, and
the distance between these two indexes will therefore enable the extreme variations
of electric current or voltage that have occurred in that period to be ascertained;
in the latter case the resistance which would be a comparatively high one is
connected across the two poles of the circuit whose voltage it is required to
record.
In cases where indications of the instrument form a basis of charge for
electricity consumed, the scale can be so calibrated as to indicate directly the
total number of units that must be consumed to average a daily use for a given
number of hours of the maximum current recorded as shown in Fig. 7, or it may
directly indicate the discount allowable to consumers as shown in Fig. 8, or the
varying prices for consumed current consequent on the consumer using a given
number of units per ampère recorded by the instrument as shown in Fig. 9; or it
may indicate the average number of hours per day the demand has been used as
shown in Fig. 10.
Figure 2 represents a different method of carrying out the invention and in this
case the liquid is contained in a syphon tube, or "D" trap C C and the expansion
of the air on being heated in bulb A causes a portion of the liquid to overflow
into the tube I and the liquid itself forms an index the height of which measured
by the scale S enables the maximum current that has passed through R to be
ascertained.
For the purposes of re-setting the instrument the whole apparatus may be tilted
around an axis concentric with the axis of A preferably, the syphon part of tube C

page_text: being set at an angle, enables the liquid in I to flow back into the syphon C,
whereby the instrument is re-set and ready for a fresh record.
Figure 2ª represents the instrument in the position of being re-set and the liquid
flowing back from the index tube I into C.
Figure 3 represents a similar instrument but with maximum and minimum index
tubes I and II.
This form is suitable for recording the maximum variations of pressure or.
voltage of an electric circuit whose two poles are connected to the ends of the
resistance R around the bulb A.
On the pressure diminishing below its normal the bulb A is heated less than
its normal amount and the liquid flows over and into the index tube I¹ to an
extent corresponding to the minimum voltage the coil R was subjected to; on the
pressure increasing above its normal value a similar record is made in tube I, so
that in this instrument maximum and minimum or total variation of pressure or
current can be recorded.
The re-setting of this form is performed in the same way as shown in Figure 2.
Figure 4 represents a maximum current recorder whose recording action depends
on the liquid in the tube C overflowing into the bulb B and on the current being
cut off and ceasing to go through R and the bulb A cooling to the same
temperature as that of B, the liquid left in the U shaped tube C retreats into a
position, leaving that portion which has overflowed trapped in the bulb B and the
shortened column of liquid in C, indicates against a scale S, the maximum current
that has passed through R.
This form of instrument may be re-set similarly to that shewn in Figure 2, as
the bulb B is set at an angle as shown on Figure 4A which on the whole tube being
tilted enables the trapped liquid in the bulb B to flow back and re-fill the U shaped
tube C.
- The invention is not confined to exactly the above forms of recording electric
meters as there are many other obvious variations or different forms of recording
differential thermometers which can be used for my invention.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is-
1st. The construction of a self recording electric meter consisting of the com-
bination of a maximum and minimum recording differential thermometer with one
of its heat receptacles or bulbs capable of being heated by a resistance through
which the current of electricity to be recorded is made to pass.
2nd. The construction of maximum and minimum electric current or pressure
recorders substantially as described and shown in accompanying drawings.
3rd. The combination of maximum electric current recording instruments and
scales giving by inspection data from which the basis of charges can be made.
Dated this 10th day of October 1893.
ARTHUR WRIGHT.