Abstract: A current measurement connector may include a first part and a second part. Each part may include a mount and a joint. The first and second part may be joined via the respective joints through a current transformer interposed between the first and second parts. The respective mounts may be configured to receive a current from a current source and pass the received current through the current transformer via the first and second parts inducing a current in the current transformer. The induced current may be useable to measure the current from the current source. Methods for fabricating the current measurement connector may include die casting the first and second parts and press fitting the first and second parts at the respective joints through the current transformer. Methods for use may include withstanding a fault current pulse and dissipating heat associated with the pulse via the first and second parts.

Abstract: The present invention relates in general to the field of integrated circuits, and more specifically to a meander resistor. Basically, a meander resistor can be considered as a bar resistor with the exception of the corner squares (right-angle bends). The Electrostatic Discharge (ESD) sensitivities of on-chip resistors can be a problem for both electronic manufactures and electronic component users. As others components, passive devices are known to be susceptible to ESD events. The context of this invention is to improve the reliability of the resistors during an ESD event. An ESD stress means that high current and high voltage levels are applied to the device. The device has to be able to dissipate this energy without failure.

Abstract: In a flat plate type thick film resistor, an insulation performance is improved by excluding the nonuniformity of potential distribution on a wiring plane, which is generated when electric current flows in a resistance wire. Simultaneously, generation of noise depending on potential distribution and variation of stray capacitance around a resistor is suppressed. When the resistance wire having a constant thickness and uniform resistivity, which is formed on an insulating substrate, is connected to a pair electrode conductors that face to each other, in the way that the resistance wire is repetitively bent to the alternate side in zigzags, a potential gradient on the wiring plane, which is generated when electric current flows in the resistance wire, is constant by properly selecting the line width, the bending angle, and the spacing between bending vertexes of a resistance wire.

Abstract: A high-performance resistor includes resistor elements electrically connected in series and each having a first and second side and a first and second end. At the first end is a first connection and provided at the second end is a second connection for connecting the resistor elements. The first and second connections each have an inner portion and an outer portion. The inner portion of the first connection is bent at a predetermined angle with respect to the first side of the resistor element. The outer portion of the first connection is in a plane which is substantially parallel to the plane of the resistor element. The inner portion of the second connection is bent at a predetermined angle with respect to the second side of the resistor element. The outer portion of the second connection is in a plane which is substantially parallel to the plane of the resistor element.

Abstract: Disclosed herein is a porous ceramic heating element wherein 0.08 to 1.00 wt % of a foaming agent is added in 99.00 to 99.92 wt % of a mixture of an inorganic material, a binder, a conductive material, a hardener, a bonding agent and a dispersion medium and mixed with the mixture. The bonding strength of porous foam formed in the ceramic heating element is increased, thereby providing an effect that the entire structure is hardened.

Abstract: The present invention relates to an electrical resistance element of the molybdenum silicide type that includes two terminals (1, 2) for the supply of electric current and at least one leg (3) which extends between the terminals and which includes a glow zone. The invention is characterized in that the glow zone has different diameters along different sections (6-11, 14-17) of the leg (3; 4, 5).

Abstract: A chip resistor is provided which includes a resistor film 5 formed between a pair of terminal electrodes 2 and 3 on an upper surface of an insulating substrate 2. The resistor film is formed with two inward grooves 7, 8 and two trimming grooves 9, 10 which are alternately provided for causing the current path in the resistor film to have a winding shape. The two inward grooves 7 and 8 are provided approximately at the midpoint between one end edge 5a and the other end edge 5b of the resistor film 5. The trimming groove 9 is provided between the inward groove 8 and the end edge 5a of the resistor film, whereas the other trimming groove 10 is provided between the inward groove 7 and the end edge 5b of the resistor film, whereby the time required for the trimming adjustment to adjust the resistance to a predetermined value is shortened, and the yield rate is reduced to reduce the cost.

Abstract: The resistor of the present invention comprises a substrate, a pair of electrodes, and a resistor element comprising rectangular sections connected to the pair of electrodes and a S-shaped section disposed between the rectangular sections and is free of trimming portion. At least one of the rectangular sections is trimmed to adjust the resistance. According to the construction of the present invention, a compact resistor of superior surge property can be obtained.

Abstract: A Resistor bank has first and second supporting member. Held on to the supporting members is a resistor element comprising a strip of resistor material which is bent into a zigzag shape. The strip is continuous and has a non-planar cross section profile. A plurality of insulating spacers mounted end to end on each of the first and second supporting members isolate the element from the first and second supporting members. The engaging surfaces of adjacent spacers are of a complimentary shape thereby to enable each spacer to move relative to each adjacent spacer with any flexing of the relevant one of the supporting members. The element is held by a plurality of clips each at a bend thereof on to a respective one of the supporting members. Each clip has at least one fastening lug for insertion into at least one fastening hole in a corresponding bend in the element.

Abstract: A heat conductor coil for heating a flowing gaseous medium is configured to be attached to a support configuration and has a heat conductor wound in windings following an ascending line of a coil to form the heat conductor coil, wherein the ascending line of the coil defines a circumferential surface of the heat conductor coil. The heat conductor is deflected alternatingly in opposite directions within the circumferential surface of the coil out of the ascending line of the coil. The heat conductor coil is attached to a support plate by securing elements having a securing part for holding a winding of the heat conductor coil and a foot part for attaching the securing element to the support plate. The securing part is a tubular section with a substantially closed mantle surface and receives a winding of the heat conductor coil.

Abstract: The invention relates to a resistor assembly for dividing an applied voltage into an intermediate voltage being below the applied anode voltage in a cathode ray tube. The resistor assembly comprises an insulating substrate and a resistive voltage divider including a first and a second resistive layer provided on the insulating substrate, and an additional resistive network with a first network terminal and a second network terminal. The additional resistive network is coupled in series with the first resistive layer. Furthermore, the additional resistive network comprises first and second resistive portions which are releasably coupled to the network terminals via bridge connections. According to the invention, the first and second resistive portions have substantially different resistance values for selecting a predetermined resistance value from a range of resistance values of the additional resistive network.

Abstract: A resistance element (19) for a device for shrinking shrinkable sleeves comprises an elongate electrical conductor extending in a zigzag pattern and bent to a tunnel shape. The shrinkable sleeve including for example an optical fiber enclosed therein is placed in that region of the resistance element (19), which corresponds to approximately the geometric axis of the upper semi-cylindric portion of the tunnel shape. The resistance element (1) has attachment pins (33) and contact and attachment pins (35) at its front and rear sides respectively intended to be placed in corresponding recesses in a lid of the device. The rear contact and attachment pins (35) have portions (39) intended for contact with elastic, electrically conducting contact pins with which the resistance element (19) comes in contact, when the lid is folded down to perform the shrinking operation.

Abstract: An inductor obtained by laminating a plurality of ceramic layers having an internal coil conductor, and a thermistor obtained by laminating a plurality of ceramic layers having internal electrodes and having a predetermined resistance-temperature characteristic are laminated via an intermediate insulating layer. Both ends of the internal coil conductor of the inductor and the internal electrodes of the thermistor are connected to a pair of external electrodes. Thus, the inductor and the thermistor are connected in parallel.

Abstract: A heating door comprises a frame. A first panel is mounted to the frame. A second panel is mounted to the frame. A sheet is disposed between the first and second panels. The sheet defines an inner section between the first panel and the sheet and an outer section between the second panel and the sheet. At least one heating mechanism is arranged in at least one of the first and the second section.

Abstract: A surface mount resistor includes an elongated piece of resistive material having strips of conductive material attached to its opposite ends. The strips of conductive material are separated to create an exposed central portion of the resistive material therebetween. According to the method the resistive strip is attached to a single co-extensive strip of conductive material and a central portion of the conductive material is removed to create the exposed central portion of the resistive strip.

Abstract: A heater (1) particularly usable as a radiant heater for electric cookers is described, which has a insulating substrate (2) of microporous thermal insulation material and at least one electric heating conductor (20) in the form of an upright, corrugated flat strip fixed to the top of the insulating substrate. The top side of the insulating substrate is structured in honeycomb-like manner and has a network of raised portions (10) between which are located roughly cylindrical depressions (11). With small-surface fixing portions the heating conductor positively engages in the raised portions (10) and is held in freely suspended manner over the insulating substrate in the vicinity of the depressions (11).

Abstract: An FBT (fly-back transformer), its bleeder resistor (installed on the top of the FBT), and a device for coupling the bleeder resistor are disclosed. The bleeder resistor 100 is accommodated within a resistor case 180, and the resistor case 180 is installed on the top of an FBT case 110. A resistor pattern 140 is printed on the substrate 130 of the bleeder resistor 100. Openings 150 are formed within the wavy portions of the resistor pattern 140, and the resistor case 180 has a plurality of isolating sheets 160 within its interior 170, so that the isolating sheets 160 can be inserted into the openings 150. When manufacturing the bleeder resistor, the glass coating, the baking, the epoxy resin dipping are eliminated, but the voltage breakdown resisting property is improved. Further, the manufacturing cost is lowered owing to the simplification of the process.

Abstract: PTC thermistors are used in reversible short circuit current limiters, in particular in series connection with electrical valves and/or capacitors. An electrically insulated, thermally conductive insulation or ceramic layer (20) is in contact electrically and with good thermal conduction via a first main surface with a metallic cooling element (25). A second main surface of the ceramic layer (20), opposite the first main surface, is covered with an electrically insulating thermal-conduction layer (21) having a thickness in the range from 10 .mu.m-100 .mu.m. Meandering tracks (16) of the resistive body of the PTC thermistor (5) are pressed between this thermal conduction layer (21) and an electrically insulating, preferably thermally conductive, flexible high-temperature stable polymer film (22). In order to provide pressure, a pressure compensation cushion (23) on which a force (F) orthogonal to the second main surface of the ceramic layer (20) acts, may be provided.

Abstract: An integrated circuit includes a string of substantially similarly-shaped resistive cells, each cell having a first resistive portion and a second resistive portion, the string having an overall orientation and at least one cell, preferably substantially all cells, and more preferably all cells have their respective centerlines oriented at non-orthogonal angles, preferably about 45 degrees, relative to the overall orientation. The cells are contiguous such that a resistor is formed by the first resistive portion of one cell and the second resistive portion of an adjacent cell. The cells preferably have a substantially hexagonal shape and are arranged into substrings. If the string includes a folding point, substrings immediately adjacent to the folding point should include an odd number, preferably three, of cells, and substrings not adjacent to the folding point should comprise an even number, preferably two, of cells.

Abstract: A resistor comprising a substantially continuous resistor element being formed into a plurality of element panels with each panel having at least two holes provided therein. Adjacent element panels are connected in series by a bend in the resistor element. At least two support tubes comprising an insulating material are provided to support the resistor element. A plurality of conductive washers are provided adjacent each hole on both sides of each element panel to provide a conductive heat sink near each support tube hole in the element panels. Insulating washers are spaced between adjacent conductive washers. Two end walls are provided adjacent opposing sides of the resistor element to receive the support tubes.

Abstract: A resistor grid assembly has a continuous resistor weave with a plurality of generally parallel, plate-like electrical elements. U-shaped bends join two adjacent elements at adjacent ends. The U-shaped bends are located in a bottom group and a top group. There is a top electrical insulating member adjacent the U-shaped bends in the top group and spaced from the U-shaped bends. There is a bottom electrical insulating member adjacent the U-shaped bends in the bottom group. Stop U-shaped pins having a pair of legs with a pair of shoulders are supported by the bottom electrical insulating member. The legs of each stop U-shaped pin extends into a pair of holes in the bottom group of U-shaped pins and rest upon the shoulders which are spaced from the insulator. Wire U-shaped pins are supported by the top electrical insulating member. The wire U-shaped pins have legs inserted into holes in the U-shaped bends in the top group. The U-shaped bends in the top group are spaced from the top insulator.

Abstract: A dynamic braking grid arrangement for reducing EMI generated by dynamic or partial regenerative electrical braking of an electric traction motor powered vehicle coupled to a wayside power source by a third rail or catenary. The grid arrangement comprises a high-power dissipation resistance grid having a plurality of separately defined resistance elements, each having a generally elongate configuration. Mounting means support each of the grid elements adjacent to and parallel with each other of the elements. A plurality of electrical conduction devices connect the elements into an electrical circuit such that current passes through at least one element in a first direction and through at least one adjacent element in a second opposite direction such that EMI generated by any one element is substantially cancelled by EMI generated by an adjacent element.

Abstract: A heat dissipating fabricated resistor grid for the dynamic braking of electric motors has a zigzag resistor supported by insulating members within a frame. The zigzag resistor is made up of a plurality of resistor elements formed from sheet metal, each element containing at least one "U" shaped bend, that are connected by welded joints between the legs of adjacent resistor elements. The resistor elements may be embossed to stiffen them. Various types of clips may be utilized to hold the tabs and the resistor elements together to facilitate welding and the clips are welded to the other components and become part of the zigzag resistor. Various types of connecting joints are provided to connect the zigzag resistor to the insulating members. Various types of securing devices are provided to secure the insulating members to a supporting metal frame.

Abstract: A strain gauge primarily designed for dynamic measurements and requiring very little force to produce a change in length. The strain gauge is alternately concave and convex in shape, such as a sinusoidal curve with nodes of low resistance on the convex portions and strain gauges of high resistance on the concave portions. The gauge is unbonded and can be stretched with very little force. The strain gauge is utilized in an instrument to monitor infant respiration and detect episodes of apnea.

Abstract: A heat dissipating resistor grid has a frame including side members carrying blocks or panels of insulating material having cavities in their inner surfaces. The resistor element is a zigzag strip formed from individual flat lengths of resistance material, each length having offset ends in opposite directions, adjoining offset ends forming a sandwich with a conductive support strip which extends beyond the offset end and terminates in projections which mate with the cavities in the insulating material. The support strip may extend into the space between the adjoining strips of resistance material forming a heat sink therein. The projecting ends of the support strip may be flat lengths, may be cut into tabs, may be formed into hollow cylinders in one piece with the support strip, may be solid cylindrical studs affixed to the support strip, or solid rod bent into U-shape with the base inside the offset ends. The insulating blocks may fit into cutouts in the frame and locked there by lateral movement.

Abstract: A resistor grid for dynamic braking and the like has a fan-folded strip of resistance material mounted in a frame. The strip is embossed longitudinally so as to stiffen it between folds or loops and lanced or slit longitudinally between embossments from fold to fold but not around folds.

Abstract: A high value, precision resistor (10) includes a doped region (18) having a boustrophedonic (folded or meandering) shape formed in a substrate (12). At least one section of the doped region (18) is formed by implantation using a focused ion beam. Where the entire doped region (18) is formed by the focused ion beam, the length thereof is selected to be large (10 to 100 times the width of the boustrophedonic shape) to maximize the accuracy of the resistor (10) by averaging over variations in grain size and implant dose. Alternatively, a probe resistor (32) and a plurality of similar unconnected doped sections (28) may be formed by means such as photolithography and flood ion implantation. The probe resistor (32) is measured at the desired operating temperature to determine the ratio of the measured resistance to the desired design resistance value.

Abstract: A resistor grid suitable for dynamic braking of diesel electric locomotives includes an upright rectangular frame with top and bottom members of insulating material and a strip of resistance material fan-folded into vertical flights between the top and bottom members. Fixtures attached to the top member suspend the fan-folded strip by its top folds and fittings affixed to the bottom member tension the fan-folded strip through its bottom folds.

Abstract: The invention relates to a method of manufacturing a heating element from a flat metal foil blank in which strips (1) are formed whose ends (2) are interconnected by connecting portions (3, 4) with alternate connecting portions disposed at opposite ends of the strips so as to form a meandering pattern and to a heating appliance incorporating such a heating element. In order to make such a foil heating element suitable for use in appliances in which an air stream to be heated passes over the foil heating element the connecting portions (3, 4) are bent in such a way that the strips (1) are tilted out of the plane of the foil blank. Preferably the strips are disposed an an angle .alpha. between 45.degree. and 90.degree. relative to the plane.

Abstract: The present device is an electrical resistor component which includes a cylindrical substrate of non-electrical conducting material. A meandering path (strongly resembling a plurality of hairpins laid end to end) of electrical conducting (but at the same time resistant to electrical current) material is secured substantially around the length dimension surface of the cylindrical substrate. The meandering path is arranged so that there is separation area of the cylindrical substrate surface which separates the turn around bends of the path which face each other. This last mentioned area has a limited amount of electrical conducting material located therein. In the separation area there are included connecting deposits of the electrical conducting material which are connected to the turnaround bends. The connecting deposits serve to provide parallel paths and thus initially reduce the electrical resistance value of the overall electrical resistor component.

Abstract: A resistor is provided with a plurality of turn parts whose corners have an obtuse flexional angle in order to improve the relative resistance precision. A ladder resistor can be formed with a plurality of such resistors connected in series, and various electronic devices are formed employing the ladder resistor.

Abstract: An electric resistance heater array having an open metal frame with multiple heater wires of heavy gauge, U-shaped Nichrome wire that are vertically spaced across the panel. The lower vertical portions of the heater wire are encased in ceramic sleeves which insulate the wire from the small apertures in the metal frame that support the wire by its constraints upon side to side and fore to aft movement.

Abstract: A structure for a resistor to be built into a cathode ray tube. The built-in resistor divides an applied anode potential into an intermediate focusing potential. The built-in resistor has a main resistor and an additional resistor means. The additional resistor means is serially connected to the main resistor. The additional resistor means provides a plurality of resistors, one of which is selected for fine adjusting the divided potential.

Abstract: A simple, highly flexible, virtually massless, temperature autoregulating heater primarily useful for soldering has an energizing circuit that may be integral with or separate from the heater element, which element has a ferromagnetic material energized via the circuit from a constant current source whereby regulation occurs about the Curie temperature of the magnetic material. The energizing circuit may be in the form of a printed circuit conductor formed on a thin layer of Kaptan or like high temperature insulating material having the heater formed on the reverse side thereof or having a sticky substance thereon so that the energizing circuit may be temporarily adhered to the heater and removed after use. Alternatively, the energizing circuit may be formed directly on Nomex paper or the like; a quite thin paper with a sticky backing.

Abstract: A resistance heating element of the ribbon type for use in a high temperature electric furnace. The element has the same curved cross-sectional configuration throughout its entire length to give it strength and stiffness and permits the element to be bent into various patterns without any overlapping portions at the bends. The curved cross-section permits the element to be supported at the bends without the element sagging reducing the amount of heat absorption by the supports and allowing greater exposure of the element.

Abstract: These resistors are obtained from conductive sheet material, for example metal sheet material (usually referred to as "grids") in which additional plates are provided in order to distribute the current density and consequently to predetermine the temperature and strain distributions caused on the resistor during load conditions.

Abstract: An electrically energizable high intensity, radiant energy heater (8) having a general M-shape for providing a pocket (20) for localized high intensity isothermal heating for fusion and fiber processing. The heater is shaped to provide easy access for a fiber (18) at an entry (16) to enable insertion of the fiber into the isothermal high temperature zone in pocket (20). A second re-entrant wall external to the pocket provides radiant shielding and buffers the isothermal heating zone from the cool environment. The heater may be constructed from a ribbon of a resistively heated metal, such as platinum foil.

Abstract: A resistance element capable of withstanding a high voltage is formed through impurity diffusion in a single crystal island of a semiconductor integrated circuit substrate. The resistance element includes a resistive region formed in an exposed surface of the single crystal island and folded reciprocatively by at least one and a half turns in a planar zigzag-like pattern. The pitch at which the resistive region is folded is decreased as viewed in the direction in which extension of depletion layer formed within the single crystal island upon application of a voltage between two ends of the resistive region is decreased.

Abstract: An improved high intensity electricl resistance heater unit comprising one or more elongate thin metal foil ribbons adapted to be heated to a high temperature by passage of electricity therethrough, a thermally insulating rigid backing for supporting each ribbon, the backing having an elongate channel in a front face thereof for receiving the ribbon with side edges of the channel being undercut to form side grooves to receive and contain longitudinal side edge portions of the ribbon to support the same along the length of the channel while leaving the major surface of the ribbon unobstructed for heat radiation therefrom. A plurality of ribbons may be mounted in the backing with all electrical metal connectors being shielded within the backing from exposure on the back face of the backing material. The ribbons may be transversely corrugated and the configuration, e.g., amplitude, of the corrugations varied along the length of the ribbons to vary the heat output along the length of the heater unit, if desired.

Abstract: The electrical resistor of the present invention comprises a flat metal plate having a thickness from 1 mil to 50 mils. A pair of electrical leads are operatively attached to the ends of the metal plate, and the side edges of the metal plate are provided with a plurality of notches extending inwardly in spaced apart relation to one another, with slots of one of the sides of the plate being staggered with respect to the slots of the other side of the plate. Each of the slots extend completely through the thickness of the plate and are formed by a laser beam cut which anneals the metal of the plate and imparts stability to the electrical characteristics of the metal plate. Once formed, the metal plate may be bent into different shapes to achieve the desired geometric configuration. Furthermore, the plate can be embedded in molded material so as to provide a protective covering for the plate.

Abstract: The electrical resistor of the present invention comprises a flat metal plate having a thickness from 8 mils to 50 mils. A pair of electrical leads are operatively attached to the ends of the metal plate, and the side edges of the metal plate are provided with a plurality of notches extending inwardly in spaced apart relation to one another, with slots of one of the sides of the plate being staggered with respect to the slots of the other side of the plate. Each of the slots extend completely through the thickness of the plate and are formed by a laser beam cut which anneals the metal of the plate and imparts stability to the electrical characteristics of the metal plate. Once formed, the metal plate may be bent into different shapes to achieve the desired geometric configuration. Furthermore, the plate can be imbedded in molded material so as to provide a protective covering for the plate.

Abstract: A gypsum wallboard with electrical heating wire disposed in grooves arranged to minimize tendencies for the board to crack when lifted by the two opposite board ends.

Abstract: Laminated heating elements are provided which are suitable for joining synthetic resinous thermoplastic bodies particularly thermoplastic foams. The heating elements are of laminar structure having at least two oppositely disposed heating elements which electrically may be fed in parallel. A significant improvement in rigidity and resistance to mechanical abuse is achieved.

Abstract: An RC composite component with a spark gap comprises a pair of discharge electrodes defining the predetermined spark gap and formed on a dielectric substrate. The discharge electrodes are coated with a film of varnish with a controlled thickness by the screen process.

Abstract: An electric resistance heating element is formed by a molybdenum disilicide wire loop formed by separate lengths of the wire having ends positioned together and butt welded to the end of a molybdenum disilicide connecting wire of larger diameter than that of the lengths. The lengths diverge from each other so they are electrically separated. Electrical connections with the free ends of the separate lengths of wire can provide for electrically powering the loop.

Abstract: An electric heating element for electric resistance furnace comprises a plurality of heater frames which consist of conductive strip material having a sectional shape selected from leg angle-section, channel-section, lip-section, T-section, U-section, V-section, I-section, H-section, Z-section, and W-section and having electric resistance. The heater frames have a configuration coinciding with a sectional shape of an inner wall of a heating chamber of the furnace, and are made and arranged to have an opening portion. Conductive connecting rods are adapted to connect both ends of each of said heater frames to alternatively adjacent ends of adjacent heater frames so as to constitute a single wire resistance body of said heater frames, and a conductive rod connected with one end of said wire resistance body is arranged to pass through said opening portion of said heater frames and facing a power source terminal together with the other end of said wire resistance body.

Abstract: A resistor with a heat sink, particularly adapted for use as a current limiter in an electrical system, such as a power transmission system. The resistor comprises a hollow tube formed of metal which offers resistance to the passage of electrical current, the tube being of a length sufficient to provide the electrical resistance for a given application. The heat sink comprises a material having a high specific heat, the material being contained within the tube and adapted to absorb heat generated by the resistance of the tube to passage of electrical current.

Abstract: An electric space heating apparatus consisting of a plurality of sections having box-like portions which by means of middle pieces are interconnected in such a way that the apparatus can extend along all the walls of the room and the zig-zag electric heating elements in the apparatus sections can be fed continuously through the complete apparatus, the apparatus being adapted to deliver the heat to the space by approximately 65-75 per cent radiation and approximately 25-35 per cent convection to circulating air, said apparatus can be easily mounted by persons without special education and authorization.

Abstract: The present device is a high reliability resistor comprising a sheet of metal foil secured to the flat side of a substrate and with the opposite side of the substrate formed to dissipate heat into the ambient thus enabling the present resistor to have an improved temperature coefficient of resistance (TCR) and further enabling the resistor to function satisfactorily in a high wattage mode.

Abstract: Heating elements comprising a ceramic article of a honeycomb structure having a positive temperature coefficient of electric resistance and composed of barium titanate are provided with channels, in which a pair of ohmic electrodes consisting mainly of silver as a metallic component and having a surface resistivity of the electrode per se of not more than 10 m.OMEGA./cm.sup.2 are provided on both end surfaces thereof and the ohmic electrodes are coated with an electrical insulating and thermostable material.