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Патент USA US2412191

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Dec. 3, 1946.
P. D. zoT‘rU
2,412,191
VOLTMETER
Filed' March 31, 1944
'
4 sheets-sheet 1
f2.7
F@ 2 '
Bydvuïßâwwavê
Dec. v3, 1946.
I P. D. zoT'rU
2,412,191
voLTMETER
Filed March 31, 1944
4 Sheets-Sheet 2
INVENTOR.
55., 3
ß 207-70.
Patented bec. 3, _1946 _
UNITED STATES PATENT OFFICE
2,4i2.19l
VOLTMETER
Paul D. Zottu, Indian Hills, Ky., assigner to
The Girdler Corporation, Louisville, Ky., a cor
poration oi’ Delaware
Application March 3l, wat, Serial No. 528,34@
6 Claims.
(Ci. lili-m95)
¿L
This invention relates to measuring instru
ments, more particularly to the measurement or"
voltages at high frequency, and has for an oh
ject the provision oi1 a wide-range voltzneter of
a simple, rugged construction and accurate 5
» throughout the Wide range of voltages which it
E
in the output circuit of the rectifier is calibrated
in terms of the line voltage or the voltage to be
measured. Hence, if the meter reads 500, the
voltage measured will be either 590 or a ñxed
multiple thereof depending upon the setting of
the spherical conductor.
`
is capable ci measuring.
For a more detailed explanation of the inven
In the development of high-frequency systems
tion and for further objects and advantages
for application to manufacturing processes there
thereof, reference is to be had to the following
has been need for a relatively simple means of lo description, taken in conjunction with the ac
measuring the voltages developed in the circuits.
comparu/ing drawings in which:
It has long been recognized that electrical energy
Fig. l is a wiring diagram, diagrammatically
at high frequency produces diathermy or inillustrating the relation oi the parts and their
ternal heating of a wide variety of materials.
associated circuits;
These materials may vary from poor conductors l5
Fig. 2 is a fractional side elevation of the high
to dielectrics or materials generally considered
as non-conductors. For such a wide variety of
voltage capacitor;
Fig. 3 is a sectional View taken on the line 3-3
applications, the voltage and frequency of the
of Fig. 5;
output circuit are adjusted to best suit a partio-
ular application.
Fic". d is a sectional view taken on the line 4_4
2li of Fig. 2;
ln accordance with the present invention, a
FS. 5 is a fractional sectional elevation taken
wide range voitineter is provided, which is rel»
on the line aïe-5 of Fig. i;
`
a'tively accurate over a range of from 500 to
Fil?. 6 diagï'amm?lîìicßlìy illustrates a mûdiñed
öûjloü volts or more. From the circuit to be
form of theinventlon;
v
tested, a voltage is applied to two series-connect~ 25
Fig. ‘7 is a plan view of an iris disc shown in Fig.
ed capacitors, one of which is adjustable between
predetermined calibrated positions. For high
voltages the adjustable capacitor preferably consfmts ci an enlarged conductor forming one plate
of the capacitor' and a fiat conductor forming 30
the other plate oi the capacitor. The flat plate
upoorted from a metallic housinsy having an
„lng above the :'iat plate. The enlarged or
.’ierical conductor is movable aient” a path nora
to the fiat plate and to the opening in the 35
using. By increasing the spacing or air gap
herr/veen the spherical conductor and the iiat
conductor, the voltmeter is set for operation to
measure voltages between differing limits. This
adjustment forms la multiplier for the voltmeter. . 4o
For low voltages, the distance between the'
spherical conductor and the ñat conductor is
relatively short. while for a voltage near the
maximum which is to be measured the distance
is substantial. The second capacitor may be i5
large in comparison with the one including the
Spherical conductor.
inasmuch as the voltage divides across the
capacitors inversely >with their capacitance, only
t; and
Fig. 8 is a plan View oi a second iris disc hav
ing a smaller opening.
Referring to the drawings, a system embody
ing the invention will ‘first be described, followed
by a more detailed description oi’ the structural
features or the multiplying capacitor. In the
system or" Fig. l, the invention is shown as com
pricing va high-voltage high-frequency vûltm‘èter‘
for the measurement of the voltage V appearing
across the terminals ill and li. This voltage di-vides across two capacitors l2 and lil, connect»
ed in series between terminals i@ and il. Both
capacitors are adjustable. For a given setting
the capacity of the capacitor i3 is usually much
larger than that of the capacitor l2. ln conse
quence, the voltage across the capacitor i3 is us
ually smaller than the voltage across the capaci
tor l2 for the reason that the-voltage divides
across the capacitors inversely with their ca
pacitance. By making the capacitor~ itl very
large in comparison with the capacitor li?, the
voltages applied to the measuring circuit may not
only be of a reasonable order of magnitude, but
a fraction of the voltage to be measured appears 50 entirely safe from an equipment and personnel
across the larger capacitor.> The fractional volt~
standpoint.
‘
age which appears across the larger capacitor is
The voltage appearing across the capacitor i3
applied to a rectiîying device which produces an
is applied by conductors it and it to a rectify
output current proportional to the applied highù
ing` device, preferably a diode lf3. The reßtiñêd
frequency voltage. A current meter connected 55 output from the diode is applied to a suitable in«
aaiaiai
3
to the measurement òf the output voltage of a
dicating device, such, for example, as a milliam
high frequency> oscillator or generator. During
meter I1, having a scale preferably calibrated in
the starting up of such an oscillator, the load is>
volts. By means of the network comprising the
to be gradually applied. Suitable adjustments
series-connected resistors I8, I9, 20 and 2|, and
of the circuit constants must be made to produce
the capacitor 22,- a substantially constant load is
maximum output . voltage. The problem is to
provided for the radiofrequency voltage which
determine whether a given change in capacitance
appears across the capacitor I3. The milliam
or lnductance is in the right direction to increase
meter I1 is connected in series with the resistor
the output voltage. Small changes in the circuit
2| which is variable or adjustable in order to
provide an initial setting for the voltmeter which il) constants frequently produce small changes inthe output voltage. These may not be of suiii
will read full-scale value for some convenient
voltage across or between conductors I4 and I5.
By means of a normally open sensitivity switch
cient magnitude to produce positive deflectiony ofv
the meterv I1. However, by temporarily closing
the sensitivity switch 25 to exclude the resistors
25, the resistors I9, 20 and 2| may be removed
I9, 20 and 2|, the sensitivity of the meter is -ma
or bypassed from the circuit of the milliammeter
terially increased. For each incremental change
I1. While the removal of these resistors greatly
of voltage, the ldeflection of the meter is mate
increases the reading and sensitivity of the meter
rially greater than with the sensitivity switch in
I1 the load across the capacitor I3 remains sub
its normally open position. Hence, whenever the
stantially constant. This result is accomplished
voltage
is low,_the sensitivity switch 25 may be
by the circuit including resistor I 8 and the ca 20
operated to by-pass the foregoing resistors and
pacitor 22 whose reactance is relatively low as
the resultant greater deflections will then indi
compared with the impedance offered by the
cate and clearly show the direction of the change
resistors I9, 20 and 2| to the radiofrequency cur
in the output voltage.
~
rent. Hence, the inclusion or exclusion of the
resistors I9-2I from the circuit does not mate 25 In terms of operation, the operator can then `
. ascertain with certainty the effect of changing
rially change the load across the capacitor I3.
'I‘he diode I6 is provided with a filament trans- ' the tuning, the- circuit constants or other variables
of the high frequency oscillator as it is brought
former 21 whose primaryv is >connected to a suit
up to full load operation. It may be observed
able source of alternating current supply 29. The
midpoint ofthe secondary winding is connected 30 again that operation of the sensitivity switch 25A
does not materially change the load across the
by conductor 30 to the indirectly heated cathode
capacitor I3 since that load is largely established ~
of the diode I6. 'I'he direct.,.-current circuit .for
by the resistor I8 and the series capacitor 22»,k
the meter I1, previously referred to, may be traced
whose reactance is relatively low as compared
from the indirectly heated cathode by way of
with the impedance offered by the resistors
conductor I4, the meter I1, conductor 32, variable
I 9-2I.
'
resistor 2|, the resistors I9g'fand 20 connected in
Coming now to the structural features charac
parallel with each other, the resistor I8 and by
terlzing the invention, the capacitor I2 comprises
` conductor I5 to the anode of the diode I6.
the conductor or electrode 35 supported by a
The initial calibration of the voltmeter-is rela
tively simple. With the spherical conductor 35 40 metallic stem 36 which is held in any desired
position by means of a split-ring clamping de
comprising the upper high voltage plate or elec
vice 31 provided with a clamping screw 38. The
trode of capacitor I2 in a position of approxi
mately maximum spacing from a iiat conductor
40 forming the other plate or electrode of the
capacitor I2, the maximum voltage for which
the meter is designed is applied. Thus, for a
live inch _spacing between the electrodes 35 and
40, a voltage of 50,000 volts may be appliedbe
tween terminals I0 and II. 'I'he frequency may
be of any value within wide limits, for example,
stem 36 as shown in Fig. 5 may be made of tubing
with the lower end plugged, and threaded for
threaded engagement with the electrode 35. As
shown, the electrode 35 is spherical in shape and
though this is the preferred construction, the
invention is not limited thereto since other shapes
, may be used.
For the higher voltages the elec
trode 35 should be provided with smooth or
rounded edges to prevent corona discharge.
from some thousands of cycles per second to a
The cooperating capacitor electrode or plate
hundred million cycles or more per second. With
t0 is shown in Fig. 3 to be circular although it
the aforesaid voltage of 50,000 (peak) volts lat a
can be of any desired configuration. Preferably
frequency of say one million cycles per second,
the capacitor I3 is adjusted until the pointer of 55 it is supported, Figs. 2 and 5, below the upper wall
dla. of a metallic housing 4I by means of an in
meter I1' is deflected to its maximum or full-scale
position. This may be accomplished by an R. F. « ' sulating supporting bar M.
voltage of the order of 100 volts across the capaci
tor I3. The capacitor I3 and the resistor 2| are
now locked in vtheir adjusted positions.
For all other voltage'ranges, the capacitor I2
is adjusted by moving spherical conductor 35 to
predetermined positions. Thus it is in effect a
multiplier and fixes the range of voltages for the
meter I1. If the meter is calibrated in volts from
0 to 500, then for the highest range the multiply
ing factor may be 100. By decreasing the spacing
between the capacitor electrodes 35 and 40 by
predetermined increments, other multiplying fac
tors in steps of III, from 1 to 100, may be provided.
Once calibrated, the voltmeter as a whole con
tinues effective as a satisfactorily accurate
measuring device.
_
The importance of the sensitivity feature will
be apparent by assuming the voltmeter is applied
This bar is carried
between adjusting nuts at the ends of threaded
screws t5- and «36 which extend downwardly
through the upper wall or cover plate Bla of
housing 5I. The iiat circular electrode 40 is fas
tened to the bar 44 by means of a threaded screw
d1 and'cooperating nut. The plate d0 is counter
sunk so that the head of screw ä'lis flush with the
upper surface thereof.
`
Just above the electrode 40 the central portion
of the housing @la is cut away to provide opening
43, shown as circular and of somewhat less di
ameter than that of the electrode 40. This open
ing is closed by means of an insulating closure
member 68, held in place by means of additional
nuts on the screws 45 and 46.
,
The movable electrode 35 is supported from
the upper plate «ila of housing «il by means of
three insulators 50, 5I and 52, which may oe of
aclarar
,
-
7
trode with respect' to said first electrode thereby
to change the voltage range of the device.
2. The combination, with a high-voltage meas
uring device in which a rectiñed current varies
in accordance with the voltage »to be measured,
of a metal plate having an opening extending
through the mid-portion thereof, a capacitor in
Y ent positions with respect to each other to change
the capacity between them and the range of volt-A
age to be measured, and shielding means, inter
posed between said two electrodes having an
opening therein for the passage therethrough of
a part only of the electrostatic field which would
otherwise extend between said two electrodes.
5. The combination, with a high-voltage high
cluding at least a first electrode and a second
4 frequency measuring device of the type in which
electrode, electrical insulating means for support
ing said i-lrst'electrode in spaced relation with 10 a rectified current varies in accordance with the
voltage to be measured, of a series-circuit includ
said opening and concentrically thereof, a plu
ing two capacitors one of which is relatively large
rality of insulating supports secured to said plate
with respect to the other, said -smaller capacitor
and extending outwardly therefrom, means in
being characterized by the provision of two elec
cluding a clamping device carried by the outer
trodes one of which is movable relative tothe
ends of said insulating members, said second elec
other. means including one of said electrodes for
trode including a supporting stem adapted to be
applying to said series-circuit the voltage to be
held by said clamping device, whereby' said last
measured, means for holding one `of said elec
named electrode may be supported in different
predetermined positions with respect to said first
electrode.
'
_
3. In a high-voltage high-frequency measuring
device in which a vrectified current varies in ac
cordance with the voltage to be measured, the
combination of a pair of series-connected capac
itors across which the voltage divides inversely
with respect to their capacities, a circuitcon
trodes in diñerent predetermined positions with
20 respect to the other to predetermine the capacity
therebetween and thereby iix the voltage range
of the measuring device, and adjusting shielding
’ means interposed between said electrodes for pre
determining the proportion of the electric ñeld
which may then exist between said electrodes
further to change the voltage range of the meas
uring device.
6. The combination, with a high-voltage meas
including a rectifying device for producing said
uring device in which a rectiñed current varies in
rectified current, a network connected in parallel
with said larger capacitor for producing a sub 30 accordance with the voltage to be measured, of a
metal plate having an opening extending through
stantially constant load across said larger ca
the mid-portion thereof, a capacitor including at
pacitor, said network including a resistor and a
least a first electrode and a second electrode, elec
third capacitor connected in series with veach
trical insulating means for supporting said first
other and in shunt across said large capacitor,
electrode in spaced relation with said opening, a
said network also including at least one additional
nected vacross the larger of said capacities and
resistor, and means for increasing the magnitude
of said rectified current Without asubstantially
changing the load across said larger capacitor
comprising a switch for removing said last-named
plurality of insulating supports secured to said
plate and extending outwardly therefrom, means
including a .clamping device carried by the outer
ends of said insulating members, said second elec
current varies in accordance with the voltage to
be measured, of a. high-voltage capacitor which
comprises electrodes relatively movable to diiîer
predetermined positions with respect to said first
40 trode including a supporting stern adapted to be
resistor from said circuit.
held by said clamping device, whereby said last
4. The combination, with a high-voltage high
named electrode may be supported in different
frequency measuring device in which a rectified
electrode.
PAUL D. ZOTTU.
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