Abstract: A conductive polymer PTC device includes upper, lower, and center electrodes, with a first PTC conductive polymer layer between the upper and center electrodes, and a second PTC conductive polymer layer between the center and lower electrodes. Each of the upper and lower electrodes is separated into an isolated portion and a main portion. The isolated portions of the upper and lower electrodes are electrically connected to each other and to the center electrode by an input terminal. Upper and lower output terminals are provided, respectively, on the main portions of the upper and lower electrodes and are electrically connected to each other. The resulting device is, effectively, two PTC devices connected in parallel, thereby providing an increased effective cross-sectional area for the current flow path, and thus a larger hold current, for a given footprint.

Abstract: An NTC thermistor element has a pair of outer electrodes formed on opposite outer end surfaces of a thermistor body made of an NTC thermistor material. A plurality of inner electrodes are formed inside this thermistor body in layers, each connected to either of this pair of outer electrodes. At least one of these layers contains a longer inner electrode and a shorter inner electrode disposed mutually opposite to each other, separated by a gap, and connected to different ones of this pair of outer electrodes. At least a portion of this longer electrode in this layer overlaps, in the perpendicular direction to the layers, another of the inner electrodes connected to the different outer electrode from the one to which this longer electrode is connected, with a thermistor layer in between.

Abstract: A temperature sensor which can be used at ordinary temperatures is provided. After a lamination plate of a phenol resin is carbonized at 640 to 750.degree. C., the powder of the carbonized material and the binder formed of a thermosetting resin, such as phenol or epoxy, are kneaded and formed into a paste, after which this paste is printed between terminals of a base film, such as polyimide, having a high resistance to heat and is calcined at a low temperature. Thus, a temperature sensor such that a resistance element is printed on the base film is obtained. The temperature sensor shows a large change of the resistance value with respect to an environment temperature change at ordinary temperatures.

Abstract: A positive temperature coefficient (PTC) resistor composition, comprising: (a) about 3% to about 75% by weight of a binder resin, (b) about 0.5% to about 70% by weight of a temperature activatable semicrystalline polymer, which is a thermoplastic elastomer (TPE) that melts at a relatively narrow temperature range to change from a crystalline state to an amorphous state, (c) about 10% to about 80% by weight of an electrically conductive material in finely particulated form selected from the group consisting of silver, graphite, graphite/carbon, nickel, copper, silver coated copper, and aluminum, (d) about 0.01% to about 80% by weight of solvent material for the composition.

Abstract: The current-limiting resistor has two connection electrodes (1, 2) which are arranged parallel to one another, a resistance body (3) which has PTC behavior and with which large-area contact is made by the connection electrodes (1, 2) and at least one varistor (4) which is in electrically conductive contact with the resistance body (3). The varistor (4) is of pillar-shaped design and has at least two first portions (4a) routed predominantly perpendicularly to the varistor axis and, arranged between said portions, a second portion (4b) having a reduced cross section compared with each of the first portions (4a). The material of the resistance body (3) fills an interspace (6), which is formed by the at least two first portions (4a) and the second portion (4b), and encloses the outwardly pointing edges (4c) of the at least two portions.This resistor can be operated at high voltages, for example 5 or 10 kV, and advantageously has a single resistance body 3 and a single varistor.

Abstract: A thermistor for surface mounting includes a first conductive terminal member, a case having a top opening, a planar thermistor element having electrodes on mutually opposite main surfaces thereof, and a second conductive terminal member having at one end thereof a planar cover part which is attached to the top part of the case. One end of the first terminal member is positioned inside the case and above its bottom member. The other ends of the first and second terminal members are positioned on the bottom surface of the case.

Abstract: An organic positive temperature coefficient thermistor contains polyethylene oxide where Mw>2,000,000 and conductive particles each having spiky protuberances. Preferably, the thermistor is prepared by blending the polyethylene oxide with the conductive particles interconnected in a chain form. The thermistor is operated at a temperature of 60 to 70.degree. C. little harmful to the human body, and has low initial resistance in its non-operating state (at room temperature), a large rate of resistance change upon transition from its non-operating state to operating state, a sharp resistance rise upon operation, and stable performance even upon repetitive operation.

Abstract: A thermistor comprising a semiconductor ceramic with an oxide spinel, which contains the elements maganese, nickel and indium. Thermistors of said composition are thermally stable and are characterized by a high resistivity and a high B-value.

Abstract: A polymer high voltage current limiter comprising, per phase, a fast circuit-breaker pole, a semi-fast protection circuit-breaker pole, and a set of polymer-based elements having very low resistivity, filled with carbon black, and connected in series and in parallel, wherein each element comprises a carbon-filled polymer matrix of elongate shape and including in its interior two parallel metal conductors.

Abstract: A current limiting device utilizes an electrically conductive composite material and an inhomogeneous distribution of resistance structure. The current limiting device has a conducting filler and at least two electrodes, where at least one of the electrodes comprises a grooved electrode structure. The grooved electrode structure maintains contact between the electrodes and the composite material, even with consumption of the composite material and production of residue during a high current condition.

Abstract: An electric resistance heating element preferably of cylindrical or prismatic shape to be inserted into a test tube, a cartridge or in another cavity has one or more conductors connected to the supply system by the use of one or more electrodes. The conductors are made of a conductive composite material of a polymeric matrix with resistive function which are formulated at such ratio and materials as to achieve an electric resistance with high positive temperature coefficient (PTC) at the operation temperatures. The electrodes may be made of metallic materials. At least a core is made of insulating material, onto which the conductors with resistive function (PTC) and the electrodes are applied.

Abstract: A surface mountable electronic device has a case with an opening, an electronic element contained inside the case such as a thermistor or a varistor that generates heats when in operation, a plurality of elongated spring terminals supporting this electronic element elastically together and each sandwiching a wall of the case both from inside and outside at a peripheral edge part of the wall at its opening, and a lid attached to the case so as to close up its opening except where the spring terminals pass through the opening. Grooves are preferably formed at peripheral edge parts of the wall where the spring terminals are fitted, contacting the wall such that heat generated by the electronic element during its operation and propagating through the spring terminals can be effectively conducted to the main body of the case and diverted from its soldered junctures with a circuit board.

Abstract: A positive thermistor device includes a positive thermistor element having a pair of opposed electrodes, each of which receives compressive force elastically applied from a corresponding one of spring contact members to hold the thermistor element at a predefined position in the device. When the thermistor device is destroyed, the element breaks into fragments, some of which remain in contact with the spring contact members. The remaining fragments deviate in position to ensure that they do not conduct electricity, resulting in an open state, wherein any current flow is inhibited through such fragments. More specifically, a positive thermistor disk is held within the device so that it is interposed between conductive spring contact pieces and insulative position-alignment projections, which are cross-diagonally situated with respect to each other.

Abstract: The present invention relates to compositions for use in forming resettable electronic circuit protection devices or fuses, methods of forming resettable fuses using the compositions, and resettable fuses formed from the compositions. Resettable fuse compositions according to the present invention include a mixture of the reaction product of polyethylene glycol and a diepoxide having a molecular weight of at least 18,000, solvent, conductive particles, and optional solvent volatility adjusters. In a preferred embodiment, resettable fuses according to the present invention are formed by screen printing the compositions directly onto printed electric circuits to form fuses. During current overload conditions, the temperature of the resettable fuse material rapidly increases due to resistive heating generated by excessive current flow through the conductive particle chains or pathways.

Abstract: A thermistor comprising a semiconductor ceramic of a mixed crystal oxide composed of rare-earth metals having the composition?Y.sub.a Gd.sub.b Sm.sub.c Tb.sub.d !.sub.2 O.sub.3,wherein0.ltoreq.a.ltoreq.0.9950.ltoreq.b.ltoreq.0.9950.ltoreq.c.ltoreq.0.9950.01.ltoreq.d.ltoreq.0.995, anda=0 if b=0, orb=0 if a=0,has a high-temperature stability and can be used at temperatures up to 1100.degree. C.

Abstract: Electrical devices having a PTC element of a polymer having conductive particles dispersed therein. The PTC element is coated with a conductive layer and has electrodes with a plurality of voids affixed to opposing surfaces. The devices are made by dispersing conductive particles into a polymer to form a polymer PTC composition. The polymer PTC composition is melt-shaped to form a laminar shaped PTC element. First and second opposing surfaces of the PTC element are coated with a conductive layer. The electrodes, characterized by a plurality of voids and made of foam, are brought into contact with the coated surfaces of the PTC element, and heated while applying pressure to form a laminate. The laminate is then further shaped into a plurality of PTC electrical circuit protection devices.

Abstract: A thermistor chip is made by first forming first metal layers with a three-layer structure at both end parts of a thermistor element and then forming second metal layers with a three-layer structure on the first metal layers so as to have edge parts that are formed directly in contact with a surface area of the thermistor element and will reduce its normal temperature resistance value. The first and second metal layers are each of a three-layer structure with a lower layer made of a metal with resistance against soldering heat, a middle layer made of a metal with both wettability to solder and resistance against soldering heat, and an upper layer made of a metal having wettability to solder.

Abstract: A thermal probe assembly has a unitary outer shell or housing forming an open end adapted to receive an electrical connector unit and having an inboard end defining a probe portion; the outer shell or housing has deformable wall portions forming a bore; a pair of terminals with electrical conductor portions connected to a thermistor have a plastics material mounting member premolded thereon; the plastics material mounting member is slidably fit in the bore to position the thermistor within the bore and to axially locate the thermistor in spaced relationship to the inboard end of the outer shell or housing; portions of the plastics material mounting member interlock with cooperating portions of the bore to operatively lock the thermistor in place within the outer shell or housing.

Abstract: A circuit protection device including a pair of terminals to be electrically connected into an electrical circuit, a pair of spaced current-carrying extensions of the terminals, and an initially low resistance current limiting device extending between the current-carrying extensions. The invention includes the feature that the current-limiting element including flexible conductive current-feeding arms having inner and outer end portions, the inner end portions thereof being electrically connected to the current-carrying extensions of the terminals. The outer end portions of the current-feeding arms are cantilevered and flexible relative to the inner end portions. The device further preferably includes a PTC current-limiting element sandwiched between the flexible outer end portions of the current-feeding arms.

Abstract: Electrical devices comprising a PTC element comprised of a polymer having conductive particles dispersed therein. The PTC element is coated with a conductive layer and has electrodes with a plurality of voids affixed to opposing surfaces. The devices are made by dispersing conductive particles into a polymer to form a polymer PTC composition. The polymer PTC composition is melt-shaped to form a laminar shaped PTC element. First and second opposing surfaces of the PTC element are coated with a conductive layer. The electrodes, characterized by a plurality of voids, are brought into contact with the coated surfaces of the PTC element, and heated while applying pressure to form a laminate. The laminate is then further shaped into a plurality of PTC electrical circuit protection devices.

Abstract: A thermistor element with positive temperature characteristic (PTC) has a planar ceramic member with a positive temperature characteristic of which the thickness is greater at its peripheral part than at the center part, decreasing either gradually or in a stepwise manner. Protrusions may be formed along its periphery. A PTC thermistor is formed with electrodes formed on both main surfaces of such a PTC thermistor, each electrode having a lower-layer electrode all over a main surface and an upper-layer electrode on the lower-layer electrode. The upper-layer electrode has a smaller surface area than the lower-layer electrode such that a portion of the lower-surface electrode is exposed at the periphery. The upper-layer electrodes may be formed at the center parts of the main surfaces, exclusive of the peripheral parts or where the protrusions are formed. The lower-layer electrodes may be mostly of Ni and the upper-layer electrodes mainly of Ag.

Abstract: An electrical apparatus comprising first and second PTC elements composed of a polymer composition with conductive particles dispersed therein, an insulating body, and first and second conductive terminals. Flexible conductive members having a first end that can be electrically connected to a source of electrical power and a second end that is adapted to receive and make electrical contact with the apparatus are provided. The PTC element and the insulating body are positioned between the first and second conductive terminals so that when the apparatus is inserted between the flexible conductive members, the members exert a pressure on the insulating body.

Abstract: An electronic device of a kind having an electronic element with a main body, terminal electrodes on the main body and lead terminals electrically connected individually to the terminal electrodes has at least a portion of the outer surfaces of the lead terminals covered with a coating resin composition containing as its resin component a saturated copolymerized polyester resin which can be dissolved in an organic solvent such that the mechanical strength of the lead terminals is improved and the insulation of the device is not compromised during its manufacture or mounting.

Abstract: A current limiting device has an electrically conductive composite material, an inhomogeneous distribution of resistance structure comprises a conducting filler, and at least two electrodes. At least one of the electrodes is a flexible electrode to maintain contact between the electrode and the composite material, regardless of the consumption of the composite material during a high current condition.

Abstract: A novel multi-layer current limiting PTC polymer device comprising at least two layers of a conductive polymer composition with electrodes attached thereto characterized by having a low contact resistance and a method of producing the same. The invention provides for the selective treatment of portions of the surface of each layer of the conductive polymer composition by at least one of plasma/corona etching and plasma sputtering/plasma spray to create a site for attachment of the electrodes resulting in a low contact resistance. The electrical devices of the invention are particularly useful in circuit protection applications.

Abstract: A thermistor with positive resistance-to-temperature characteristic used in a overcurrent protection circuit has electrodes on mutually opposite main surfaces and is mounted to a substrate having electrically conductive members such that deterioration of its voltage resistance due to heat emission can be controlled. A spacer with smaller thermal conductivity than the substrate and penetrated by a conductor piece with a small cross-sectional area is inserted between solder materials connecting to one of the thermistor electrodes. The other electrode is contacted by an elongated connecting member through its sectional surface transverse to its longitudinal direction such that the cross-sectional area of electrical conduction is reduced.

Abstract: Self-regulating heating element for heating a gaseous flowing medium with a strip conductor (1) and a control conductor (2) which are electrically connected to one another in series and are in thermal contact with one another over their length, but which are electrically insulated from one another. The Control conductor (2) is preferably formed of a jacketed conductor with a metallic jacket which is electrically connected to the strip conductor (1).

Abstract: The invention is directed to a positive temperature coefficient heater. A pair of electrical conductors are connected to a positive temperature coefficient body at respective locations. A dielectric material is attached to the body between the conductors and prevents electrical arcing around the body between the conductors.

Abstract: Low voltage current limiting fuses wherein the conventional fusible element is replaced. The fuses of the invention are resettable manually or automatically such that the fuse need not be physically replaced following a fault current or overload current occurrence in the external circuit in which the fuse is incorporated.

Abstract: A housing contains a PTC element which can be easily inserted and removed. Conductive metal retaining elements of the housing are secured to the base of the housing, and retain the PTC element with a generally planar portion parallel to the electrodes of the PTC component. The retaining elements also have slidable contact between the elements and the top of the housing so as to modify the elastic deformation of the element and allow for insertion and removal of the PTC element.

Abstract: A ceramic heating element has been conventionally driven by direct-current voltage, but the direct-current voltage causes a problem in the heating element. Therefore, in a method of the present invention, an alternating current is supplied to the heating element by changing a direct current, so that deformation of the heating element can be prevented and reliability can be improved.

Abstract: A positive characteristic thermistor device includes a device main body made of a semiconductor ceramic material which reliably and cleanly delaminates upon the application of excessive voltage thereto. The main body has outer layers having lower porosity formed on both sides of an inner layer having higher porosity. The inner layer having higher porosity can be obtained by burning a ceramic material for positive characteristic thermistors including resin beads mixed therein. After forming the main body, an electrode is formed on the outer surface of each of the outer layers. When an overvoltage is applied to this positive characteristic thermistor device, delamination occurs in the inner layer having higher porosity to create an open-circuit in a circuit in which the thermistor device is connected.

Abstract: Circuit protection device having a PTC element in series with a fusible element. The device includes a PTC element having first and second electrodes in electrical contact with the PTC element. An insulating layer is disposed on the first and second electrodes. Portions of the insulating layer are removed to form first and second contact points. A first conductive layer is in electrical contact with the first electrode and wraps around the PTC element. A portion of the first conductive layer forms a fusible element. A second conductive layer is in electrical contact with the second electrode. The wrap-around configuration of the device allows for an electrical connection to be made to both electrodes from the same side of the electrical device. The wrap-around configuration also permits current to flow in series through the PTC element and the fusible element for added protection from overcurrent conditions.

Abstract: An electrical device having a resistive element having a first electrode in electrical contact with the top surface of the resistive element and a second electrode in electrical contact with the bottom surface of the resistive element. An insulating layer is formed on the first and second electrodes. A portion of the insulating layer is removed from the first and second electrodes to form first and second contact points. A conductive layer is formed on the insulating layer and makes electrical contact with the first and second electrodes at the contact points. The conductive layer has portions removed to form first and second end terminations separated by electrically non-conductive gaps. The wrap-around configuration of the device allows for an electrical connection to be made to both electrodes from the same side of the electrical device.

Abstract: The present invention discloses a surface-mount resistance-temperature-detector (RTD) supported on a substrate. The surface-mount RTD includes a resistive strip disposed on a top surface of the substrate having a substantially linear temperature resistance coefficient (TCR) over a predetermined temperature range for measurement. The surface-mount RTD further includes two top terminals disposed on two opposite end on the top surface of the substrate wherein each of the top terminal connected to one end of the resistive strip. The surface-mount RTD further includes two bottom terminals disposed on a bottom surface of the substrate wherein each of the bottom terminals is disposed below one of the top terminals. The surface-mount RTD further includes two edge conductive plates each disposed on an edge surface of the substrate connected to one of the top terminals to a corresponding bottom terminal below.

Abstract: A current-limiting device comprises at least one polymer-based electrically conducting body with two contact surfaces and at least two electrodes. Close to a first one of the two contact surfaces of the polymer-based electrically conducting body, a surface layer is arranged. The resistivity of the surface layer is reduced relative to the resistivity of the bulk of the polymer body, and at the same time at least the second contact surface of the body is adapted to make free contact with at least one of the electrodes or other electrically conducting body.

Abstract: A temperature sensor, which is used particularly in the intake tube of internal combustion engines in conjunction with an air flow rate meter, includes a sensor element that is constructed as a temperature-dependent NTC resistor in the form of a pill, a cube or the like. A large number of identical temperature sensors are produced by applying a plurality of parallel conductor tracks, which include partial conductor tracks, to a glass plate or wafer, by providing the conductor tracks with outer solderable contact surfaces and inner solderable contact surfaces, by applying and electrically conductively connecting each sensor element to a first partial conductor track, by conductively connecting the sensor element to a second partial conductor track, by coating the sensor element with a resist layer, and by cutting apart the wafer with parallel cuts extending between the individual sensor elements.

Abstract: An electrical resistance temperature sensor (11) contained in a stainless steel, tubular jacket (12), which has a very small diameter of approximately 1 mm, a platinum resistance coil (18) running between two joining bolts (14, 19). The resistance coil with a positive temperature characteristic of the resistance is placed in an embedding medium (17), which comprises a mixture of magnesium oxide or aluminium oxide and cerium dioxide.For use as an integrating temperature sensor for a catalytic converter, said adequately flexible temperature sensor can be wound into a roll of smooth and corrugated metal sheets and fixed by soldering in vacuo.

Abstract: An electrical device comprising a resistive element having a first electrode in electrical contact with the top surface of the resistive element and a second electrode in electrical contact with the bottom surface of the resistive element. An insulating layer is formed on the first and second electrodes. A portion of the insulating layer is removed from the first and second electrodes to form first and second contact points. A conductive layer is formed on the insulating layer and makes electrical contact with the first and second electrodes at the contact points. The conductive layer has portions removed to form first and second end terminations separated by electrically non-conductive gaps. The wrap-around configuration of the device allows for an electrical connection to be made to both electrodes from the same side of the electrical device.

Abstract: A novel current limiting PTC polymer device and methods of making the same comprising a current limiting polymer composition with porous electrodes interfaced therewith such that a low contact resistance results using a combination of (1) extrusion attachment of the current limiting polymer composition to the porous electrodes, (2) careful selection of the electrode materials in view of the conductive filler and/or conductive metal particles in the current limiting polymer composition, and (3) plasma treatment of the attachment surfaces of the current limiting polymer composition preceding and/or during the extrusion attachment process. The invention provides for the selective treatment of portions of the surface of the current limiting polymer composition by at least one of plasma etching and metallizing to create attachment surfaces for extrusion attachment of porous electrodes resulting in a low contact resistance, mechanical stability and a reduced potential for arcing in the electrode/polymer interface.

Abstract: An improved temperature compensation method is disclosed in which a temperature sensing thermistor is formed on a substrate whose temperature is to be series of fractional thermistors which are selectively shorted out during a manufacturing process to provide a compensation for manufacturing variabilities of the temperature coefficient of resistance of the thermistor.

Abstract: Circuit protection devices comprising PTC elements and circuits containing such devices. The PTC element includes a crystalline conductive polymer composition comprising a conductive particulate filler grafted to a modified polyolefin. The modified polyolefin comprises a polyolefin having a carboxylic acid or a carboxylic acid derivative grafted thereto. The conductive particulate filler is grafted via an esterification reaction to the modified polyolefin.

Abstract: A resistor formed by a laminated structure having a resistance body interposed between two conductive plates, electrical connection members being connected to the conductive plates, and a method for manufacturing the resistor. The resistor includes a first connection portion formed on a first conductive plate by partially cutting off a laminate part of a second conductive plate and the resistance body, and a second connection portion formed on the second conductive plate by partially cutting off a laminate part of the first conductive plate and the resistance body. The method for manufacturing the resistor includes the steps of applying solder to one of the two conductive plates and the resistance body, thereafter passing the component through a high temperature oven and thereby melting the solder, and fixing the resistance body and the two conductive plates together in an electrically conductive state with the resistance body interposed between the two conductive plates, by solidifying the solder.

Abstract: A small-size high-performance electronic protective device (10) is provided for use in protecting communication equipment including an exchange servicing module against application of abnormal surge current due to accidental shorts between adjacent ones of power feed lines in a communications system. The protective device (10) includes positive thermistors (3a, 3b) connected between communication link input terminals (1a, 1b) and output terminals (1c, 1d) coupled to an associative equipment being protected. The protective device (10) also includes thick-film resistive elements (5a, 5b), which are connected in parallel with the thermistors (3a, 3b), respectively.

Abstract: A ceramic heater includes a body of aluminum nitride, and a heating element embedded in the body of aluminum nitride. The heating element has a resistance of (E.sup.2 /W).multidot.0.003.OMEGA. to (E.sup.2 /W).multidot.0.135.OMEGA. (E and W denote an input voltage (unit: V) and a weight (unit: g) of the body of aluminum nitride, respectively).

Abstract: Electrical devices, particularly circuit protection devices, contain conductive polymer elements whose edges are formed by breaking the conductive polymer element, along a desired path, without the introduction of any solid body into the element. The resulting cohesive failure of the conductive polymer produces a distinctive fractured surface. One method of preparing such devices involves etching fracture channels in the electrodes of a plaque containing a PTC conductive polymer element sandwiched between metal foil electrodes, and then snapping the plaque along the fracture channels to form individual devices.

Abstract: A high-temperature gas sensor for the detection of the heat tone of combustible gases includes a semiconducting ceramic layer with thermistor properties. The semiconducting ceramic layer is formed of an oxide ceramic semiconducting material having a defined crystalline structure and a thermistor characteristic of high sensitivity. A process for the manufacture of the high-temperature gas sensor includes sintering a loosely structured layer of powder particles of an oxide semiconductor with both a defined composition and high sinter activity for achieving a required high porosity of a semiconducting ceramic layer with thermistor properties.

Abstract: Circuit protection devices comprising PTC elements and circuits containing such devices. The PTC element includes a crystalline conductive polymer composition comprising a conductive particulate filler grafted to a modified polyolefin. The modified polyolefin comprises a polyolefin having a carboxylic acid or a carboxylic acid derivative grafted thereto. The conductive particulate filler is grafted via an esterification reaction to the modified polyolefin.

Abstract: The current-limiting resistor has two connection electrodes (1, 2) which are arranged parallel to one another as well as a resistance body (3) which has PTC behavior and with which large-area contact is made by the connection electrodes (1, 2). A varistor (40) is in electrically conductive contact with the resistance body (3). The resistance body (3) contains two contact areas (50, 51) as well as a response point (60) which is connected in parallel with the varistor (40) via the two contact areas (50, 51) and implements a PTC transition above a threshold value of a current flowing through the resistor.Since the resistance body effects the electrical contact with the varistor (40) in the case of this resistor, no metal connection electrodes are required for the varistor. At the same time, due to the outward displacement of the response point (60) away from the varistor (40), the operational reliability of the resistor is considerably improved.

Abstract: A varistor and a PTC resistor formed from a composite material containing a polymer matrix and a filler. The varistor experiences two nonlinear changes caused by the current due to applied voltage, the varistor comprising a composite material comprising a filler and a polymer matrix, the filler consisting of particles of grained microstructure. The PTC resistor experiences a first nonlinear dependency of resistivity at a first PTC temperature resulting from an interaction of the filler and the polymer matrix and a second nonlinear dependency of resistivity at a second, lower PTC temperature resulting from the filler.