US2988700A - Potential indicating device - Google Patents

Description

June 13, 1961 1. ROSINEK 2,938,700

POTENTIAL INDICATING DEVICE Filed May 20, 1954 4 Sheets-Sheet 1 ATTORNEY 4 Sheets-Sheet 5 BATTEKIE$ l l /0Z L l. ROSINEK POTENTIAL INDICATING DEVICE hrk l5. 7

June 13, 1961 Filed May 20, 1954 INVENTOR ISIDORE ROSINEK BY 4 2w ATTORNEY I States Patent C) 2,988,700 POTENTIAL INDICATING DEVICE Isidore Rosinek, 1520 E. 2nd St., Brooklyn 30, N .Y. Filed May 20, 1954, Ser. No. 431,215 7 Claims. (Cl. 324-122) This invention relates to devices for indicating the presence of a wide range of potentials, from 80 volts to infinity and has for an object the provision of such :a device which is safe and reliable, and which consists mainly of an actuating device and an indicator, or a combinational actuating device and indicator.

Another object. of the invention is the use of a cold cathode trigger tube as the actuating device in a high potential indicating device.

Yet another object of the invention is the provision, in a high potential indicating device, of a cold cathode trigger tube in combination with a circuit including nonlinear safety resistance means connected in parallel.

A further object of the invention is the provision, in apparatus of the character described, of a combined actuating and indicating device and comprised of a small neon tube with a third element built'in, adapted to function as a trigger tube and adapted to produce sufiicient illumination to function as an indicator.

Another object of the invention is the provision of a test stick including a series of high resistors terminating in a contact electrode on one extremity thereof, having a sufficient collective resistance to reduce the current therethrough to 1 milliampere or less, and a main circuit connected thereto including a Thyrite non-linear safety resistor, a cold cathode tube, comprising an actuating device, extinguishing circuit means, calibrating means, sensitizing means, checking means for said extinguishing circuit means, test circuits and switching means to render the same effective, and means to supply direct current thereto of the order of L10 to 150 volts, so as to have a striking voltage of not less than 80 volts.

A further object of the invention is the provision, in a device of the character described, of a circuit including a cold cathode tube as an actuating device, and having it positioned to be visible to a user as an indicating dew'ce, and a transparent or translucent colored cap or the like for preventing photo-electric effects of light upon said tube.

Another object of the invention is the provision of a potential indicator including circuits built around a cold cathode trigger tube and powered by means other than the circuit being tested.

Another object of the invention is the provision of a potential indicator which employs a cold cathode gas filled tube having not less than three elements connected in a safety circuit between the conductor to be tested and ground potential.

A further object of the invention is the provision of a cold cathode trigger tube in an opaque enclosure having an opening therein so that the cold cathode trigger tube functions additionally as an indicator, and the provision of a transparent cap or bubble which allows the tube to be seen when it is illuminated, yet eliminating any photoelectric action in said tube. I

A further object of the invention is the provision of a potential operated cold cathode gas filled thyratron type of tube in which the grid is allowed to assume control of the tube by means of an oscillating direct current plate circuit in which the plate voltage is momentarily caused to dip to the point where the plate-cathode circuit is rapidly interrupted and yet at the same time maintaining the grid characteristics of the tube.

A further object of the invention is the provision of a system of the character described in which the plate cir- Patented June 13, 1961 ice 2 cuit includes a relay winding whereby the relay may control remote systems in time with actuating potentials impressed on the grid of the gas filled cold cathode thyratron tube.

A further object of the invention is the provision of a circuit of the character described, in which the plate circuit has the primary of a transformer connected thereto so that the pulses of the plate circuit may be transformed into alternating current on the secondary thereof.

Other objects and advantages of the invention will be apparent to those skilled in the art upon a study of this specification and the accompanying drawings.

Referring to the drawings, which are given by way of example to illustrate the invention:

FIGURE 1 is a circuit diagram of one form of the invention;

FIGURE 2 is a circuit diagram similar to the diagram of FIGURE 1 with certain modifications;

FIGURE 3 is a circuit diagram showing further modifications of the circuit shown in FIGURE 1;

FIGURE 4 is a view of a test stick made according to Q the invention;

FIGURE 5 is a cross-sectional view showing a preferred arrangement of resistors, insulators, and casing in the high tension end of the test stick;

FIGURE 6 is a view of the test stick taken along the line 6-6 of FIGURE 4;

FIGURE 7 is a circuit diagram of a two unit potential indicator system for detecting the presence of high potentials on conductors;

FIGURE 8 is a diagram of a portion of the circuit of FIGURE 7, showing the circuit'relation of certain of the components when a switch therein is switched to another position;

FIGURE 9 is a diagrammatic sketch showing the use of two test sticks, in combination with a modification of the main circuit, for detecting phase angle diiferences;

FIGURE 10 is a circuit diagram similar to the diagram of FIGURE 1 and showing relay means for effecting controls in time with the firing of the thyratron tube; and

FIGURE 11 is a diagrammatic circuit showing a transformer with its primary interconnected with the plate circuit so that the direct current impulses are transformed into alternating or pulsating currents so that the secondary of the transformer may be connected to suitable instrumentalities to be controlled in tune with the action in said circuit.

My new and improved test sticks and the circuits embodied in them have the following important features:

(1) They are of a convenient and most useful length without being unwieldy, andthey are comparatively light in weight and yet they are devised to stand rough handling.

(2) The range of the circuits embodied in my sticks for average commercial applications, whether they are portable or fixed installations is from 250 volts to 50,000 volts or higher, AC. of any standard power frequency, or DC. positive or negative; and this circuit constitutes a complete conductive circuit extending from the conductor being tested to ground.

(3) Cold cathode tubes are employed in my circuits, they also function as indicators, and photo-electric action is minimized by means of a closure which also constitutes a light filter.

(4) The circuit includes a number of rapidly made tests to insure the safety of the workers.

Referring now to FIGURE 1, a series of five resistors R, have one extremity 10 constituting the tip of the stick, and the other extremity 11 is connected to a circuit which forms the heart of my system, and which will be presently described. The values of these five resistors depends on the maximum voltages on the conductors to be encountered with the test stick, at any event it is preferable that the total resistance be of such value that low resultant currents of the order of 1 milliampere or less. Between the point 11 and the ground clamp 12, is connected a non-linear safety resistor R of the Thyrite type. A bus wire 13 is connected to the point where the lower end of the resistor R is connected to ground 12, and a second paralleling bus wire 14 has one end connected to the junction of R and R and its other end is connected to an electrode 15 of a cold cathode gas filled tube 16.

The tube 16 has a cathode 17 which is connected via a wire 19 to the bus wire 13, so that the Thyrite type resistor and the gas filled tube 16 are virtually connected in parallel. The third element 18 of the tube is connected via a branch conductor 20 to an extinguisher circuit C R constituting a condenser C with a resistor R in parallel therewith, and thence to the terminal 2 1 of a source of DC.

The third element 18 is also connected via a conductor 23 to a parallel circuit R C which in turn is connected via a conductor 24 to a contact 25 on a double pole double throw test switch SW2. A condenser C is connected between one end of a resistor R and the bus wire 13, and the other end of the resistor R is connected via a wire 33 to one mid-terminal 32 of the switch SW2. The resistor R is a current limiting resistor, and the condenser C together with R is a test circuit.

A resistor R termed a calibrating resistor, has one end connected to the bus wire 14, and the other end is connected via a wire 34 to the contact 26 on switch SW2. The resistor R also has said last end connected, via a wire 35, to a series of test resistors R-, which are, in turn, connected to contact 31 on SW2.

A resistor R termed a sensitizing resistor, has one end connected to the bus wire 14 and its other end is connected to a contact 36 on switch SW1. Contact 38 is connected via a wire 37 to the bus wire 13 and to a contact 27 on SW2. A condenser C connected in parallel with the bus wire 13 and wire 14 functions as an A.C.-D.C. equalizer. In some instances, I wish to include a relay winding serially between the point 2-1 and the point where the condenser C and resistor R are connected to the wire 20a for controlling other instrumentalities in time with the firing of the tube 16.

FIGURE 2 shows a circuit which is substantially identical with that shown in FIGURE 1, except for a modifi: cation. All circuit components in FIGURE 2 having the same numerals as those in FIGURE 1 are identical with those already described in connection with FIGURE and the following different components are: The wire 23 leading from the control element 18 in the tube 16, has a branch wire 41 connected thereto, and this wire leads to a neon tube 40, which is, in turn connected to the terminal 21 via a wire 42, an extinguisher circuit C R and via a wire 43 to the terminal 21. In using the circuit of FIGURE 2, the steps are the same as for FIGURE 1, except that the neon tube, may be used for an indicator instead of using the trigger tube 16 for the purpose.

The circuit shown in FIGURE 3 is substantially the same as that shown in FIGURE 1 except that in, place of the series of resistors R I employ a plurality of capacitors C connected in series. One end of the series is connected at the point 11 and the other end is connected to the tip electrode 10. The capacitors C comprise a sufficient number having values to limit the firing load to a maximum of one mill as a safety factor for the person holding the stick, for instance, as was the case above in connection with FIGURE 1. Since the other elements of the circuit are the same as in FIGURE 1, it is believed to be unnecessary to describe them again in connection with FIGURE 3 especially since the numerals on the various elements of the circuit are the same as those in FIGURE 1.

The elements of the circuits shown in FIGURES l,

4 2 and 3, and any variations thereof may be built into a test stick such as that shown in FIGURE 4. The test stick shown in FIGURE 4 is a completely self contained and portable unit which may be used anywhere.

Before describing the entire test stick, reference is made to FIG. 5 which shows a portion of the high tension end of the test stick and one preferred embodiment of a novel method of mounting the resistors forming the series R of FIG. 1 or 2. In cases where capacitors such as C are used, the method of mounting them and connecting them to the electrode tip 10 is similar to the method of mounting the resistors which will now be described.

The electrode 10 is mounted in an insulator 45 which has a tubular shank 46 and a tapered apex 47, the taper being such as to form a shoulder 48 adjacent to the shank 46. A tubular insulator '50 has an interior wall 49. Forming a fit within the wall 49 is a tubular insulator 51 which has a tubular wall 52 and a perforated head 53 forming a closure-for one end thereof. The other end has a portion 54 of reduced diameter, the purpose of which will be presently described.

The interior bore 55 of the insulator 51 forms a socket into which one end of a resistor 56 may be positioned. Adjacent to the head 53, a cupped metallic spring washer 57 is positioned and this may be made of any suitable material such for example, as bronze. A screw 58 has a shank 59 extending through the perforate head 53 and is screwed into one end of a helical spring 60 and the electrode 10 may have a corresponding threaded portion 62 to be screwed into the other end of the spring thereby forming a resilient connection between the washer 57 and the electrode 10. The second insulator is generally H-shaped in cross section and carries opposed sockets 63 and 64 for the reception of the ends of resistors such as the resistor 56. At the bo tom of the socket 63 is a spring washer 57 and likewise at the bottom of the socket 64 is a second spring washer 57 and these are mechanically connected by a metallic screw 66 passing through a central hole in a wall 67 defining the bottoms of said sockets.

The screw 66 passing through both spring Washers 57 engages a nut 61 making electrical contact between the spring washers 57. The insulator 65 has a portion 68 of reduced diameter at one end thereof and a portion 69 of reduced diameter at the other end thereof. The diameters of the portions 68 and 69 are also of the portion 64 being substantially the same.

The resistor 56 is positioned in one end of one of the sockets of a neighboring insulator so that it is in contact with the spring washers therein and is wholly supported by said sockets. Since several resistors are employed in my new and improved test stick, the ends of the other insulators are mounted in sockets in insulators identical with the insulator 65, it is not believed necessary to describe each and every one over again. However, the last one in the series, namely, the insulator 70 is cylindrical in form and it has a socket 71 formed in one end thereof which faces the nearest insulator 65 and cooperates with the latter to support the last resistor 56 in the series. A spring washer 57 is positioned in the bottom of the socket 71 and a screw 72 similar to the screw 58 extends through a central passage 73 formed therein and is connected to said last spring washer. This conductor connects to the bus wire 14 shown in FIG. 1 or 2. The insulator 70 is substantially identical with the insulator 51 and has a portion 74 of reduced diameter similar to the portion 54 surrounding the socket 71 and its diameter is preferably substantially the same as that of portions 54, 68 and 69. A tubular insulating sleeve 75 forms a working fit on the portion 54 and 68, for example, as it is preferably slightly shorter than the distance between the shoulders adjacent to said portions of reduced diameters, when the resistor 56 is positioned in the sockets 55 and 63.

Returning now to FIGURE 4, the test stick has a high tension portion formed of insulators and resistors gssavos such as described above and this portion may be socketed into a boss 76 having a flange 77. Spaced apart from the flange 77 is a second flange 78 which forms the base for a compartment 79 containing the elements shown in the circuit of FIGURE 1. Between the flanges 77 and 78 is a spacer member 81, and passing through this spacer is a conduit 82 through which the bus wire 14 extends into the compartment 79. The components are all enclosed within this compartment with the exception of the cold cathode trigger tube 16, which extends through the casing of the compartment 79 so as to be visible to a user. In order to prevent or minimize photoelectric action in the tube 16, it is covered with a dome 83 of transparent or translucent material and of a color to filter out rays of light which would tend to cause photoelectric action within the tube.

Joining the compartment 79 is a tubular member 84 which forms the main handle of the test stick and which may contain a battery, for example, 150 volts to furnish the necessary potentials to test and operate the stick. The inner end of the battery is connected to the terminal 21 and the outer end of the battery is connected to the negative side 22 of the circuit. The handle member 84 has a closure disk 85 and it supports a spring 86 which maintains the battery in contact with the points 21 and 22 at all times. A cable 87 is connected to the ground, which is the negative bus wire 13 and it terminates in a ground clamp or clip 12.

Use of test stick In order to determine the presence of potentials on conductors, the following steps are taken, the circuit of FIGURE 2, having a battery of 135-150 volts connected to the terminals 21 and 22:

(1) Connect the ground clamp or clip 12 to ground.

(2) Throw switch SW2 to the test position, thereby connecting the point 32 to the point 31, by means of the blade 29, and at the same time connecting the point 27 to the point 25 by means of the blade 28. When this is done, the visual indicator 16 should pulsate. If it does, the tip should then be touched to ground and the indicator should go out due to the fact that when this is done the voltage or potential is thereby reduced to a value too low to trigger the indicator. When the tip 10 is removed from ground, the indicator should light up again, due to the fact the test circuit is changed to the extent that the potential across the indicator and actuator tube is sufficient to again fire it.

(3) Throw the test switch SW2 to the normal position where the blade 29 connects contacts 32 and 30 together and the blade 28 connects contacts 27 and 26 together. Then touch the tip 10 to the conductor to be tested, and if the indicator 16 lights, the conductor is alive.

(4) Step #2 is repeated in its entirety to double check the stick circuit, and if it checks all right it is believed safe to assume that the indications obtained in Step 3 are reliable.

In the form of the invention shown in FIGURES 7 and 8, two units are shown, one designated as 88 may comprise the test stick per se with'its cold cathode combined actuator and indicator and a second unit 90 which is arranged to be connected or disconnected from the test stick unit 88, the connection being made via a 2-wire shielded cable 89. The power unit is connected to a suitable source of current by means of a wire 91 and a ground wire 92. Suitable sources of power are as follows:

Alternating current 60 cycles, 110 to 135 volts Alternating current 25 cycles, 110 to 135 volts Direct current with a positive live leg and the negative leg grounded Dry (B) batteries such as are described above herein in connection with FIGURES 1 to 4.

The stick unit 88, FIGS. 7 and 8, includes a series of high resistors, R which has one end connected to an electrode 10, and the other end is connected to a non- 6 linear resistor R and to a conductor 93 which is com nected to the control element or grid 94 in the cold cathode tube 16. The other end of the non-linear resistor is connected to a conductor 95 which is in turn connected to the cathode 97 and to the ground wire 96.

Bridged across the conductors 93 and 96 is a calibrat-' ing resistor R and this is bridged by a condenser 0., which functions as an equalizer for alternating currents. The anode 15 of the tube '16 is connected to a resistor R which is bridged by a condenser C (constituting an extinguishing circuit), and resistor R is in turn connected via a wire 98 to the positive terminal 99 of the power supply and this in turn is adapted to be connected to a suitable source of current as will presently be described.

Bridged across the conductors 93 and 95 is a resistor R which in some respects is similar to the resistor R described above for controlling the sensitivity of the circuit. In series with the resistor 3 is a switch SW3 for throwing the resistor R into and out of the circuit. The conductor 96 carries a detachable coupling 100 and like wise the shield 95 has a terminal 101.

The above described elements comprising the test stick per se may be connected to any suitable source of current, as was pointed out above and in the first example B batteries of 150 volts have their negative terminal 102 connected to a conductor 103 and the positive terminal 104 is connected through a switch 105 to a bus wire 106. When the switch 105 is closed, current is supplied to the conductor 106 via the choke 107 which is positioned between filter condensers 108 and 109. A volt meter 110 has one terminal connected to a bus wire 111 which is in effect an extension of the wire 106 (through the choke 107), and the other side is connected to the bus wire 103 whenever a switch 112 is closed. The wire 111 is connected to the terminal 99 and the wire 103 is connected to the terminal 101 as is the ground wire 113 and this ground wire is connected to the ground wire 96 through the terminal 100.

Where 60 cycle alternating current is used as the source of current, the wires 91 and 92 are connected to it, so that current coming over the wire 91 passes through a rectifier 114 and thence it passes through the filter system comprised of the filter condenser 108, the choke 107 and the filter condenser 109 and from the filter system the rectified current is delivered by the terminal 99 to the anode of the cold cathode tube 16. A four-pole double throw switch 115 has a blade 116 which cooperates with contacts 117 and 118; a blade 119 which cooperates with contacts 120 and 121. It also has a blade 122 which cooperates with contacts 123 and 124 and a blade 125 which cooperates with contacts 126 and 127. A condenser 128 is connected between the switch blades 116 and 122 and a pair of condensers 129 and 130 is connected in series with each other and to the switch blades 119 and 125. A mid-tap 131 is connected through a limiting resistor 132 to a test plate 133. The bus wire 111 is connected via a wire 134 to the switch contacts 117 and 123, and the switch contact 127 is connected via a wire 135 to the bus wire 103 which is the negative side of the source and which is also ground.

The purpose of the above arrangement is to provide potentials greater than the supply voltage for the purpose of testing the test sticks. For example, if the source of current connected across 91 and 92, is, for example, 110 volts and 60 cycles, it is by the time it is rectified and reaches the volt meter, in the neighborhood of 100 volts. Now, with the switch in the position shown in FIG. 7, the condenser 128 is connected across the approximately 100 volt filtered potential.

The series condensers 129 and 130 are also connected across this potential and they are likewise charged up to 100 volts. Now, when the switch 115 is thrown to the position shown in FIG. 8, the condenser 128 is connected in series with series condensers 129 and 130 so that the mid-tap 131 impresses upon the test plate 133 approximately 50 volts of potential from the condenser 130 plus 100 volts from the condenser 128, making a total of 150 volts to be added to the 100 volt supply to, obtain 250 Volts. Obviously, by the same method, I can, by increasing the number of poles in the switch and utilizing more condensers, provide any desired potential from the comparatively low voltage source.

The test plate 133 is preferably not directly connected to the conductor 131 instead I find it very convenient to yieldingly mount the test plate on its support so that when the tip of the test stick is touched to it (with the light pressure) the test plate is moved into contact with the conductor 131.

Referring now to FIGURE 9, a further modification is shown for detecting phase angle differences.

In alternating current distribution and transmission systems where power is supplied over many parallel paths, it is necessary, when paralleling circuits, that each have the same phase angle. The potential indicating device may be modified and utilized for the purpose of determining that it is safe to close switches, or circuit breakers in such circuits. The sensitivity control 150 may be adjusted so as to give indications whenever the phase angle exceeds a predetermined value.

The phasing may be done directly on high voltage equipment without the necessity of utilizing potential transformers and other instrumentalities heretofore employed.

In FIGURE 9, conductors 137 and 138 may be of different phases or they may be of the same phase but it is assumed that the phase relations are unknown. If 137 were phase A and the phase of 138 were unknown, the device would be used to determine whether or not the two were in phase; a switch 139 may be positioned between them to be closed when it is safe to do so. A modified double test stick has corresponding tips 10 and 10a which form the extremities of resistors R and RR respectively. These may each be comprised of a series of resistors (for example, resistors) similar to those described in connection with FIGURE 1 above. In the modification, the non-linear resistor R has one end connected to the lower extremity of R which is designated by the numeral 14 and has its other end connected at 141 to the lower extremity of the resistor RR A bus wire 142 is connected to the point 140, and a second bus wire 143 is connected to the point 141. The bus 142 is connected via a branch wire 144 to an electrode 15 of a cold cathode gas filled tube 16. The tube 16 has a cathode 17 which is connected via a branch wire 145 to the bus wire 143. Thus, the tube 16 is actually connected in parallel with the non-linear resistor R The third element 18 of the tube 16 is connected through an extinguisher circuit C R constituting a condenser C with a resistor R in parallel therewith and thence to the plus terminal 146 up a battery 148, which is substantially the same as either of those described herein above. Between the tube 16 and the non-linear resistor R I provide a phase angle sensitivity control 150 which is connected in parallel with the resistor R and the tube 16. The negative terminal 147 of the battery 148 is connected via a wire 151 to the bus wire 142 thus completing the circuit of the phase angle detector.

Use of the device for detecting phase angle differences It is pointed out above that the conductor 137 was connected to a known phase, for example, phase A and that the conductor 138" was connected to an unknown phase which might be A or B; Now, with the stick positioned so that the electrode is in contact with the conductor "137 and with the electrode 10a in contact with the conductor 138, the phase relation can be determined.

If the trigger tube 16. lights up thisindicates. that the two.conductors are not in phase with each other and thereforethe switch. should not be closed. If; on the other hand, the tube 16remainsdark, the; switch may be, safely c osed. ca s h t c nduc o s ar n n se. Of

course, the device should be tested beforehand, and one method of testing it would be to individually test the branch with the electrode 10 on it in a manner similar to that described herein in connection with that in FIGURE 1 and then portion carrying the electrode 10a can be tested in the same manner as described above herein to make sure the both branches of the device are operable.

Further modification of the device of FIGURE 9 contemplates the provision in place of the sensitivity control (which may be a variable resistor). I provide at least two such resistors in series each being individually adjustable so that by means of one of them, I can (1) pre-set the device to a desired operating voltage being tested and (2) I can pre-set for a desired phase angle so that the lighting of the trigger tube would indicate a phase difference in excess of the desired phase angle.

Referring to FIGURE 10, I show a circuit winding 152 connected in series with the conductor 20, between the combined capacitor resistor C R and the positive terminal 21 of the Source of current. The relay has switching contacts 153, 154 which control a device 155 remote from the relay by connecting it to a source of current such as the source 156.

FIGURE 11, a further modification is ShOWn wherein the primary winding 157 of a transformer 158 is connected between the capacitive resistance network C R and the plus terminal of the direct current source of current 21. The transformer 158 also has a secondary winding 159 which is connected in a circuit with a device adapted to utilize alternating current for example a lamp 160. In both of the modifications (FIGURE 10 and FIGURE 11), the remote control is effected in definite time relation to the firing of the tube.

Although I have herein described two systems for indicating the presence of potential on electrical conductors and some modifications thereof, it will be understood that these are given by way of example to illustrate the invention and how to practice it and is not intended to be limitative, as many changes may be made in the arrangements shown and described within the scope of the following claims.

I claim:

1. In a device for indicating the presence of potentials on electrical conductors, a circuit having current limiting means therein for limiting the current passing through said device to a predetermined value, a gas filled tube in said device adapted to function both as an actuator and as an alarm indicator and having at least an anode, a cathode, and a control element, a connection between said control element and one end of said current limiting means, a second connection between said cathode and ground, non-linear resistance means connected in parallel with the connections to said control element and cathode, an extinguisher circuit connected between said anode and one side of a source of current independent of any potential present on said conductors, and desensitivity control means connected in parallel with said resistance means and having a switch serially included in said connection, the other side of said source being connected to ground, thereby constituting means to supply a firing potential to said tube.

2. In a device for indicating the presence of potentials on electrical conductors, a circuit having current limiting means therein; a cold cathode gas filled thyratron tube in said device having at least an anode, a cathode, and a control element; a connection between said control element and one end of said limiting means, a second connection between said cathode and ground, non-linear resistance means connected in parallel with said control element and cathode, an extinguisher circuit connected between said anode and a first side of a source of current independent of any potentials present on said electrical conductors, and including a resistance-capacitor combination adapted-t0 produce the effect of momentary reducing theplate potential. to allow the grid to reassume control of. the, cir uit without appreciably changing the characteristics of said tube, and a connection between the other side of said source and ground, forming with said first connection to said source, means to supply a firing potential to said tube.

3. In a device for indicating the presence of potentials on electrical conductors, a circuit having current limiting means therein, non-linear resistance means connected between one end of said current limiting means and ground; a gas filled tube in said device having at least an anode, a cathode, and a control element, said control element and cathode being connected in parallel with said nonlinear resistance means; an extinguisher circuit connected between said anode and one terminal of a source of current, the other side of said source being connected to ground, test circuit means interconnected with the elements of said tube and including switching means which normally connects said calibrating resistor in parallel with said non-linear resistor, said calibrating resistor comprising means for equalizing said circuit so as to make it equally effective on both alternating and direct current; said switching means when in a test position, being adapted to check said extinguisher circuit and to impress a test circuit; which includes a capacitor and resistance means, in series with said calibrating resistor for determining whether said device is in operative condition.

4. In a portable test stick for indicating the presence of electrical energy on conductors, a circuit having current limiting means therein, a gas filled tube in said device having at least an anode, a cathode, and a control element, said control element and cathode being connected in parallel with non-linear resistance means connected to said limiting means and ground respectively, a battery having its positive terminal connected to said anode via an extinguisher circuit, and a negative terminal being connected to ground, a calibrating resistor in parallel with said non-linear resistor, test circuit means interconnected with the elements of said tube and including double pole double throw switching means which normally connected said calibrating resistor in parallel with said non-linear resistor, said switching means when in a test position being adapted to check said extinguisher circuit and to impress a test circuit, which includes a capacitor and resistance means, in series with said calibrating resistor for firing said tube if said device is in operative condition.

5. In a portable test stick for indicating the presence of potentials on electrical conductors, comprising a tubular portion of one diameter, a second tubular portion larger in diameter than said first portion, and a housing intermediate said portions, current limiting means in said first portion having one end terminating in a tip electrode, a battery in said second portion and having means for connecting the negative terminal thereof to ground, a nonlinear resistor connected between the other terminal of said current limiting means and ground; a gas filled tube throw switching means which normally connects a calibrating resistor in parallel with said non-linear resistor; said switching means being adapted to be thrown to a test position to check said extinguisher circuit and being adapted to impress a test circuit, which includes a capacitor and resistor means, in series with said calibrating resistor for determining whether said device is in operative condition or not.

6. In a device of the character described, an input circuit having current limiting means therein for limiting the value of current therethrough; a gas filled cold cathode tube having an anode, a cathode and a control grid; said grid and cathode being connected to said current limiting means and to ground, respectively, non-linear resistance means connected in parallel with said last connections, an extinguisher circuit connected between said anode and one side of a source of direct current, a connection between the other side of said source and ground, said extinguishing circuit comprising a combination of a resistor and a condenser in parallel, said control element being adapted to control the firing of said tube, whereby the charging current of the condenser causes the anode circuit to fire after the grid circuit has been fired and then extinguished by the rapid discharge of said condenser via the resistor connected in parallel therewith and effecting intermittent operation of said circuit during which the grid reassumes control without materially changing the characteristics of the grid circuit or the grid-anode transfer voltage and current.

7. A device according to claim 6 in which the connection from the other side of the said source of current extends to the cathode of said tube and in which each of said current limiting means constitutes an array of resistors of such values as to limit the possible current flow to a predetermined quantity.

References Cited in the file of this patent UNITED STATES PATENTS 1,744,840 Streiby et a1. Jan. 28, 1930 1,795,176 Lloyd Mar. 3, 1931 1,906,644 Sleeper May 2, 1933 2,093,854 Swart Sept. 21, 1937 2,284,423 Hansell May 26, 1942 2,482,016 McCoy Sept. 13, 1949 2,632,785 Knopp et al. Mar. 24, 1953 2,637,786 Bordevieck May 5, 1953 2,648,817 Schiedel Aug. 11, 1953

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