Patent Description:
Resistive heaters are used in a variety of applications to provide heat to a target and/or environment. One type of resistive heater known in the art is a cartridge heater, which generally consists of a resistive wire heating element wound around a ceramic core. A typical ceramic core defines two longitudinal bores with power/terminal pins disposed therein. A first end of the resistive wire is electrically connected to one power pin and the other end of the resistive wire electrically connected to the other power pin. This assembly is then inserted into a tubular metal sheath of a larger diameter having an open end and a closed end, or two open ends, thus creating an annular space between the sheath and the resistive wire/core assembly. An insulative material, such as magnesium oxide (MgO) or the like, is poured into the open end of the sheath to fill the annular space between the resistive wire and the inner surface of the sheath.

The open end of the sheath is sealed, for example by using a potting compound and/or discrete sealing members. The entire assembly is then compacted or compressed, as by swaging or by other suitable process, to reduce the diameter of the sheath and to thus compact and compress the MgO and to at least partially crush the ceramic core so as to collapse the core about the pins to ensure good electrical contact and thermal transfer. The compacted MgO provides a relatively good heat transfer path between the heating element and the sheath and it also electrically insulates the sheath from the heating element.

In order to determine the proper temperature at which the heaters should be operating, discrete temperature sensors, for example thermocouples, are placed on or near the heater. Adding discrete temperature sensors to the heater and its environment can be costly and add complexity to the overall heating system.

<CIT> discloses a system according to the preamble of claim <NUM>.

In one form, a heater system is provided, which includes a plurality of heaters, a controller for supplying power to the plurality of heaters, a plurality sets of auxiliary wires extending from the plurality of heaters, a plurality of connector parts connected to the sets of auxiliary wires, each connector part being configured to be connected to another connector part directly or via connecting wires, and a wire harness for connecting the plurality sets of auxiliary wires to the controller. Each set of auxiliary wires includes a temperature sensing wire, an auxiliary power supply wire, and an auxiliary power return wire, wherein in each set of auxiliary wires, the temperature sensing wire is joined to one of the auxiliary power supply wire and the auxiliary power return wire to form a thermocouple junction, and the material of the temperature sensing wire is different from the one of the auxiliary power supply wire and the auxiliary power return wire such that each of the plurality of heaters is operable to function as both a heater and a temperature sensor.

In other features, the temperature sensing wire is made of a first conductive material, and the auxiliary power supply wire and the auxiliary power return wire are made of a second conductive material. The first conductive material is a copper-nickel alloy and the second conductive material is a nickel-chromium alloy. The thermocouple junction is joined to an end of a resistive heating element of each heater. The wire harness further includes a main power supply wire and a main power return wire directly connected to the controller, wherein one of the main power supply wire and the main power return wire is made of a same material of the temperature sensing wires.

In still other features, the wire harness further includes a main power supply wire and a main power return wire, wherein the main power supply wire and the main power return wire are selectively connected to a same connector to route one of heaters as a stand-alone heater or selectively connected to different connectors such that at least some of the heaters are connected in series.

In other features, the temperature sensing wire is made of a first conductive material, and the auxiliary power supply wire and the auxiliary power return wire are made of a second conductive material different from the first conductive material. The first conductive material is a copper-nickel alloy, and the second conductive material is a nickel-chromium alloy. The one heater of the plurality of heaters includes a resistive heating element, and the thermocouple junction is joined to an end of the resistive heating element.

The embodiments of <FIG> are not embodiments of the invention but are useful for understanding the invention.

Referring to <FIG>, a heater according to the teachings of the present disclosure is illustrated and generally indicated by reference numeral <NUM>. The heater <NUM> in this form is a cartridge heater, however, it should be understood that the teachings of the present disclosure may be applied to other types of heaters as set forth in greater detail below while remaining within the scope of the present disclosure. As shown, the heater <NUM> comprises a resistive heating element <NUM> having two end portions <NUM> and <NUM>, and the resistive heating element <NUM> is in the form of a metal wire, such as a nichrome material by way of example. The resistive heating element <NUM> is wound or disposed around a non-conductive portion (or core in this form) <NUM>. The core <NUM> defines a proximal end <NUM> and a distal end <NUM> and further defines first and second apertures <NUM> and <NUM> extending through at least the proximal end <NUM>.

The heater <NUM> further comprises a first power pin <NUM> that is made of a first conductive material and a second power pin <NUM> that is made of a second conductive material that is dissimilar from the first conductive material of the first power pin <NUM>. Further, the resistive heating element <NUM> is made of a material that is different from the first and second conductive materials of the first and second power pins <NUM>, <NUM> and forms a first junction <NUM> at end <NUM> with the first power pin <NUM> and a second junction <NUM> at its other end <NUM> with the second power pin <NUM>. Because the resistive heating element <NUM> is a different material than the first power pin <NUM> at junction <NUM> and is a different material than the second power pin <NUM> at junction <NUM>, a thermocouple junction is effectively formed and thus changes in voltage at the first and second junctions <NUM>, <NUM> are detected (as set forth in greater detail below) to determine an average temperature of the heater <NUM> without the use of a separate/discrete temperature sensor.

In one form, the resistive heating element <NUM> is a nichrome material, the first power pin <NUM> is a Chromel® nickel alloy, and the second power pin <NUM> is an Alumel® nickel alloy. Alternately, the first power pin <NUM> could be iron, and the second power <NUM> could be constantan. It should be appreciated by those skilled in the art that any number of different materials and their combinations can be used for the resistive heating element <NUM>, the first power pin <NUM>, and the second power pin <NUM>, as long as the three materials are different and a thermocouple junction is effectively formed at junctions <NUM> and <NUM>. The materials described herein are merely exemplary and thus should not be construed as limiting the scope of the present disclosure.

In one application, the average temperature of the heater <NUM> may be used to detect the presence of moisture. If moisture is detected, moisture management control algorithms can then be implemented via a controller (described in greater detail below) in order to remove the moisture in a controlled manner rather than continuing to operate the heater <NUM> and a possible premature failure.

As further shown, the heater <NUM> includes a sheath <NUM> surrounding the non-conductive portion <NUM> and a sealing member <NUM> disposed at the proximal end <NUM> of the non-conductive portion <NUM> and extending at least partially into the sheath <NUM> to complete the heater assembly. Additionally, a dielectric fill material <NUM> is disposed between the resistive heating element <NUM> and the sheath <NUM>. Various constructions and further structural and electrical details of cartridge heaters are set forth in greater detail in <CIT> and <CIT>, which are commonly assigned with the present application. Therefore, it should be understood that the form illustrated herein is merely exemplary and should not be construed as limiting the scope of the present disclosure.

Referring now to <FIG>, the present disclosure further includes a controller <NUM> in communication with the power pins <NUM>, <NUM> and configured to measure changes in voltage at the first and second junctions <NUM>, <NUM>. More specifically, the controller <NUM> measures millivolt (mV) changes at the junctions <NUM>, <NUM> and then uses these changes in voltage to calculate an average temperature of the heater <NUM>. In one form, the controller <NUM> measures changes in voltage at the junctions <NUM>, <NUM> without interrupting power to the resistive heating element <NUM>. This may be accomplished, for example, by taking a reading at the zero crossing of an AC input power signal. In another form, power is interrupted and the controller <NUM> switches from a heating mode to a measuring mode to measure the changes in voltage. Once the average temperature is determined, the controller <NUM> switches back to the heating mode, which is described in greater detail below. More specifically, in one form, a triac is used to switch AC power to the heater <NUM>, and temperature information is gathered at or near the zero-cross of the power signal. Other forms of AC switching devices may be employed while remaining within the scope of the present disclosure, and thus the use of a triac is merely exemplary and should not be construed as limiting the scope of the present disclosure.

Alternately, as shown in <FIG>, a FET <NUM> is used as a switching device and means of measuring voltage during an off-period of the FET with a DC power supply. In one form, three (<NUM>) relatively large resistors <NUM>, <NUM>, and <NUM> are used to form a protective circuit for the measurement circuit <NUM>. It should be understood that this switching and measurement circuit is merely exemplary and should not be construed as limiting the scope of the present disclosure.

Referring back to <FIG>, a pair of lead wires <NUM> are connected to the first power pin <NUM> and the second power pin <NUM>. In one form, the lead wires <NUM> are both the same material such as, by way of example, copper. The lead wires <NUM> are provided to reduce the length of power pins needed to reach the controller <NUM>, while introducing another junction by virtue of the different materials at junctions <NUM> and <NUM>. In this form, in order for the controller <NUM> to determine which junction is being measured for changes in voltage, signal wires <NUM> and <NUM> may be employed such that the controller <NUM> switches between the signal wires <NUM> and <NUM> to identify the junction being measured. Alternately, the signal wires <NUM> and <NUM> may be eliminated and the change in voltage across the lead wire junctions <NUM> and <NUM> can be negligible or compensated through software in the controller <NUM>.

Referring now to <FIG>, the teachings of the present disclosure may also be applied to a heater <NUM>' having a plurality of zones <NUM>, <NUM> and <NUM>. Each of the zones includes its own set of power pins <NUM>', <NUM>' and resistive heating element <NUM>' as described above (only one zone <NUM> is illustrated for purposes of clarity). In one form of this multi-zone heater <NUM>', the controller <NUM> (not shown) would be in communication with the end portions <NUM>, <NUM>, and <NUM> of each of the zones in order to detect voltage changes and thus determine an average temperature for that specific zone. Alternately, the controller <NUM> could be in communication with only the end portion <NUM> to determine the average temperature of the heater <NUM>' and whether or not moisture may be present as set forth above. Although three (<NUM>) zones are shown, it should be understood that any number of zones may be employed while remaining within the scope of the present disclosure.

Turning now to <FIG>, the teachings of the present disclosure may also be applied to a plurality of separate heaters <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, which may be cartridge heaters, and which are connected in sequence as shown. Each heater comprises first and second junctions of the dissimilar power pins to the resistive heating element as shown and thus the average temperature of each heater <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> can be determined by a controller <NUM> as set forth above. In another form, each of the heaters <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> has its own power supply pin and a single power return pin is connected to all of the heaters in order to reduce the complexity of this multiple heater form. In this form with cartridge heaters, each core would include passageways to accommodate power supply pins for each successive heater.

Referring now to <FIG> and <FIG>, a pitch of the resistive heating element <NUM> may be varied in accordance with another form of the present disclosure in order to provide a tailored heat profile along the heater <NUM>. In one form (<FIG>), the resistive heating element <NUM> defines a continuously variable pitch along its length. More specifically, the resistive heating element <NUM> has a continuously variable pitch with the ability to accommodate an increasing or decreasing pitch P<NUM>-P<NUM> on the immediately adjacent next <NUM> degree coil loop. The continuously variable pitch of resistive heating element <NUM> provides gradual changes in the flux density of a heater surface (e.g., the surface of a sheath <NUM>). Although the principle of this continuously variable pitch is shown as applied to a tubular heater having filled insulation <NUM>, the principles may also be applied to any type of heater, including without limitation, the cartridge heater as set forth above. Additionally, as set forth above, the first power pin <NUM> is made of a first conductive material, the second power pin <NUM> is made of a second conductive material that is dissimilar from the first conductive material of the first power pin <NUM>, while the resistive heating element <NUM> is made of a material that is different from the first and second conductive materials of the first and second power pins <NUM>, <NUM> so that changes in voltage at the first and second junctions <NUM>, <NUM> are detected to determine an average temperature of the heater <NUM>.

In another form (<FIG>), the resistive heating element <NUM> has pitches P<NUM>, P<NUM>, and P<NUM> in zones A, B, and C, respectively. P3 is greater than P1, and P1 is greater than P2. The resistive heating element <NUM> has a constant pitch along the length of each zone as shown. Similarly, the first power pin <NUM> is made of a first conductive material, the second power pin <NUM> is made of a second conductive material that is dissimilar from the first conductive material of the first power pin <NUM>, while the resistive heating element <NUM> is made of a material that is different from the first and second conductive materials of the first and second power pins <NUM>, <NUM> so that changes in voltage at the first and second junctions <NUM>, <NUM> are detected to determine an average temperature of the heater <NUM>.

Referring to <FIG>, the heater and dual purpose power pins as described herein have numerous applications, including by way of example a heat exchanger <NUM>. The heat exchanger <NUM> may include one or a plurality of heating elements <NUM>, and each of the heating elements <NUM> may further include zones or variable pitch resistive heating elements as illustrated and described above while remaining within the scope of the present disclosure. It should be understood that the application of a heat exchanger is merely exemplary and that the teachings of the present disclosure may be employed in any application in which heat is being provided while also requiring a temperature measurement, whether that temperature be absolute or for another environmental condition such as the presence of moisture as set forth above.

As shown in <FIG>, the teachings of the present disclosure may also be applied to other types of heaters such as a layered heater <NUM>. Generally, the layered heater <NUM> includes a dielectric layer <NUM> that is applied to a substrate <NUM>, a resistive heating layer <NUM> applied to the dielectric layer <NUM>, and a protective layer <NUM> applied over the resistive heating layer <NUM>. A junction <NUM> is formed between one end of a trace the resistive layer <NUM> and a first lead wire <NUM> (only one end is shown for purposes of clarity), and similarly a second junction is formed at another end, and following the principles of the present disclosure as set forth above, voltage changes at these junctions are detected in order to determine the average temperature of the heater <NUM>. Such layered heaters are illustrated and described in greater detail in <CIT>, which is commonly assigned with the present application and the contents of which are incorporated herein by reference in their entirety.

Other types of heaters rather than, or in addition to the cartridge, tubular, and layered heaters as set forth above may also be employed according to the teachings of the present disclosure. These additional types of heaters may include, by way of example, a polymer heater, a flexible heater, heat trace, and a ceramic heater. It should be understood that these types of heaters are merely exemplary and should not be construed as limiting the scope of the present disclosure.

Referring now to <FIG>, a method of controlling at least one heater in accordance with the teachings of the present disclosure is shown. The method comprises the steps of:.

In another form of this method, as shown by the dashed lines, step (B) is interrupted while the controller switches to a measuring mode to measure the change in voltage, and then the controller is switched back to the heating mode.

Yet another form of the present disclosure is shown in <FIG>, wherein a heater for use in fluid immersion heating is illustrated and generally indicated by reference numeral <NUM>. The heater <NUM> comprises a heating portion <NUM> configured for immersion into a fluid, the heating portion <NUM> comprising a plurality of resistive heating elements <NUM>, and at least two non-heating portions <NUM>, <NUM> contiguous with the heating portion <NUM> (only one non-heating portion <NUM> is shown in <FIG>). Each non-heating portion <NUM>, <NUM> defines a length and comprises a corresponding plurality of sets of power pins electrically connected to the plurality of heating elements <NUM>. More specifically, each set of power pins comprises a first power pin <NUM> made of a first conductive material and a second power pin <NUM> made of a second conductive material that is dissimilar from the first conductive material of the first power pin <NUM>. The first power pins <NUM> are electrically connected to the second power pins <NUM> within the non-heating portions <NUM>, <NUM> to form junctions <NUM>, <NUM>, and <NUM>. As further shown, the second power pins <NUM> extend into the heating portion <NUM> and are electrically connected to the corresponding resistive heating elements <NUM>. Further, the second power pins <NUM> define a cross-sectional area that is larger than the corresponding resistive heating element <NUM> so as to not create another junction or measurable amount of heat at the connection between the second power pins <NUM> and the resistive heating elements <NUM>.

As further shown, a termination portion <NUM> is contiguous with the non-heating portion <NUM>, and the plurality of first power pins <NUM> exit the non-heating portion <NUM> and extend into the termination portions <NUM> for electrical connection to lead wires and a controller (not shown). Similar to the previous description, each of the resistive heating elements <NUM> are made of a material that is different from the first and second conductive materials of the first and second power pins <NUM>, <NUM>, and wherein each of the junctions <NUM>, <NUM>, and <NUM> of the first power pin <NUM> to the second power pin <NUM> is disposed at a different location along the lengths of the non-heating portions <NUM>, <NUM>. More specifically, and by way of example, junction <NUM> is at a distance L<NUM>, junction <NUM> is at a distance L<NUM>, and junction <NUM> is at a distance L<NUM>.

As shown in <FIG>, with temperature of the junctions <NUM>, <NUM>, and <NUM> over time "t," the junction <NUM> is submerged in the fluid F, the junction <NUM> is submerged but not as deep in the fluid, and the junction <NUM> is not submerged. Accordingly, detecting changes in voltage at each of the junctions <NUM>, <NUM>, and <NUM> can provide an indication of the fluid level relative to the heating portion <NUM>. It is desirable, especially when the fluid is oil in a cooking/fryer application, that the heating portion <NUM> not be exposed to air during operation so as to not cause a fire. With the junctions <NUM>, <NUM>, and <NUM> according to the teachings of the present disclosure, a controller can determine if the fluid level is too close to the heating portion <NUM> and thus disconnect power from the heater <NUM>.

Although three (<NUM>) junctions <NUM>, <NUM>, and <NUM> are illustrated in this example, it should be understood that any number of junctions may be employed while remaining within the scope of the present disclosure, provided that the junctions are not in the heating portion <NUM>.

Referring now to <FIG>, yet another form of the present disclosure includes a plurality of heater cores <NUM> arranged in zones of a heater system <NUM> as shown. The heater cores <NUM> in this exemplary form are cartridge heaters as described above, however, it should be understood that other types of heaters as set forth herein may also be employed. Accordingly, the cartridge heater construction in this form of the present disclosure should not be construed as limiting the scope of the present disclosure.

Each heater core <NUM> includes a plurality of power pins <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> as shown. Similar to the forms described above, the power pins are made of different conductive materials, and more specifically, power pins <NUM>, <NUM>, and <NUM> are made of a first conductive material, power pins <NUM>, <NUM>, and <NUM> are made of a second conductive material that is dissimilar from the first conductive material. As further shown, at least one jumper <NUM> is connected between dissimilar power pins, and in this example, power pin <NUM> and power pin <NUM>, in order to obtain a temperature reading proximate the location of the jumper <NUM>. The jumper <NUM> may be, for example, a lead wire or other conductive member sufficient to obtain the millivolt signal indicative of temperature proximate the location of the jumper <NUM>, which is also in communication with the controller <NUM> as illustrated and described above. Any number of jumpers <NUM> may be used across dissimilar power pins, and another location is illustrated at jumper <NUM> between power pin <NUM> and power pin <NUM>, between ZONE <NUM> and ZONE <NUM>.

In this exemplary form, power pins <NUM>, <NUM>, and <NUM> are neutral legs of heater circuits between adjacent power pins <NUM>, <NUM>, and <NUM>, respectively. More specifically, a heater circuit in ZONE <NUM> would be between power pins <NUM> and <NUM>, with the resistive heating element (e.g., element <NUM> shown in <FIG>) between these power pins. A heater circuit in ZONE <NUM> would be between power pins <NUM> and <NUM>, with the resistive heating element between these two power pins. Similarly, a heater circuit in ZONE <NUM> would be between power pins <NUM> and <NUM>, with the resistive heating element between these two power pins. It should be understood that these heater circuits are merely exemplary and are constructed according to the teachings of a cartridge heater described above and with reference to <FIG>. Any number and configurations of heater circuits with multiple heater cores <NUM> and zones may be employed while remaining within the scope of the present disclosure. The illustration of four (<NUM>) zones and a cartridge heater construction is merely exemplary and it should be understood that the dissimilar power pins and jumpers may be employed with other types of heaters and in a different number and/or configuration of zones while remaining within the scope of the present disclosure.

Referring now to <FIG>, in one form, a heater <NUM> is configured to include a primary sensing junction that can be arranged within the heater <NUM> or outside the heater <NUM> for measuring temperature. The heater <NUM> includes a resistive heating element <NUM>, a first power pin <NUM>, and a second power pin <NUM>. The resistive heating element <NUM> has a first end and a second end. The first power pin <NUM> is connected to the first end of the resistive heating element <NUM> to form a first junction <NUM>, and the second power pin <NUM> is connected to the second end of the resistive heating element <NUM> to form a second junction <NUM>. The first power pin <NUM> and the second power pin <NUM> are operable to supply power to the heating element <NUM> by way of the controller.

The second power pin <NUM> includes a first lead wire <NUM> and a second lead wire <NUM>. The first lead wire <NUM> is connected to the second end of the resistive heating element <NUM> to form the second junction <NUM>, and the second lead wire <NUM> is connected to the first lead wire <NUM> to form a primary sensing junction <NUM> at a first reference area. The second lead wire <NUM> is configured to connect the resistive heating element <NUM> to the controller by way of the first lead wire <NUM>.

In one form, the first lead wire <NUM> and the second lead wire <NUM> are made of dissimilar conductive materials or more particularly, materials having different Seebeck coefficients. For example, various combinations of nickel alloys, iron, constantan, Alumel® or the like may be used. The difference in material of the first lead wire <NUM> and the second lead wires <NUM> is represented by the different style lines in <FIG> (e.g., dash line for the second lead wire <NUM> and dashed-dotted line for first lead wire <NUM>). Since the materials are different, the primary sensing junction <NUM> is effectively a thermocouple to generate a voltage change that is measured to determine a temperature at the first reference area. Accordingly, in this form, the junctions <NUM> and <NUM> for connecting to the resistive heating element <NUM> is separated from a sensing location. Thus, the heater <NUM> is not restricted to detecting temperature at the ends of the heating element <NUM>, and a temperature measurement may be detected at various locations within the heater <NUM>. Furthermore, in one form, the first lead wire <NUM> and the second lead wire <NUM> are configured to have the primary sensing junction <NUM> outside of the heater <NUM>.

As discussed with respect to <FIG>, the controller (not shown in <FIG>) is in communication with the first power pin <NUM> and the second power pin <NUM> and is configured to supply power to the resistive heater element <NUM> via the power pins <NUM> and <NUM>. The controller is also configured to calculate the temperature at the first reference area based on the voltage change created by the sensing junction <NUM> using the Seebeck coefficients of the materials.

In one form, the resistive heating element <NUM>, the first power pin <NUM>, and the first lead wire <NUM> of the second power pin <NUM> are made of the same conductive material or of materials with similar Seebeck properties (i.e., substantially the same Seebeck coefficients). Accordingly, a voltage change created by the first junction <NUM> and the second junction <NUM> is substantially zero, and the temperature measurement determined by the controller is based on the voltage change created by the primary sensing junction <NUM>.

In another form, the resistive heating element <NUM>, the first power pin <NUM>, and/or the first lead wire <NUM> of the second power pin <NUM> are made of different conductive materials. With such configurations, the material of the second lead wire <NUM> is selected such that the Seebeck coefficient of the second lead wire <NUM> is the most dissimilar from that of the resistive heating element <NUM>, the first power pin <NUM>, and the first lead wire <NUM> of the second power pin <NUM>. Accordingly, the primary sensing junction <NUM> is provided as the largest contributor to overall temperature measurement, and any temperature measurement from the first and second junctions <NUM> and <NUM> are minimized.

As discussed above, the temperature can be detected at the zero-crossing of the power signal. Alternatively, the controller is configured to switch between a heating mode for directing power to the resistive heating element and a measuring mode for measuring changes in voltage at the primary sensing junction <NUM> to determine the temperature at the reference area.

Referring to <FIG>, in one form, a heater <NUM> includes two sensing junctions in proximity to each other to detect a temperature at a virtual point between the two sensing junctions. Here, the heater <NUM> comprises a resistive heating element <NUM>, a second power pin <NUM>, and a first power pin <NUM>. The resistive heating element <NUM> comprises a first end and a second end. The first power pin <NUM> forms a first junction <NUM> with the first end of the heating element <NUM>, and the second power pin <NUM> forms a second junction <NUM> with the second end of the heating element <NUM>. The second power pin <NUM> is configured in a similar manner as the second power pin <NUM> of <FIG>, and thus, includes a first lead wire <NUM> that is connected to the resistive heating element <NUM> to form the second junction <NUM>, and a second lead wire <NUM> that is connected to the first lead wire <NUM> to form a first primary sensing junction <NUM> at a first reference area within the heater <NUM>.

In this form, the first power pin <NUM> is configured in a similar manner as the second power pin <NUM>, and comprises two lead wires (i.e., a third lead wire <NUM> and a fourth lead wire <NUM>) to form a sensing junction. More particularly, the third lead wire <NUM> is connected to the first end of the resistive heating element <NUM> to form the first junction <NUM>, and the fourth lead wire <NUM> forms a second primary sensing junction <NUM> with the third lead wire <NUM> at a second reference area. The second primary sensing junction <NUM> is provided at a second reference area of the heater <NUM> that is adjacent and proximate to the first reference area having the first primary sensing junction <NUM>. While the sensing junctions <NUM> and <NUM> are provided as within the heater <NUM>, the sensing junctions <NUM> and <NUM> can also be provided outside the heater <NUM>.

Similar to the second power pin <NUM>, the third lead wire <NUM> is made of a different conductive material than that of the fourth lead wire <NUM>, and is of different conductive material as that of the second lead wire <NUM> of the second power pin <NUM>. Accordingly, the second primary sensing junction <NUM> is effectively a thermocouple used in conjunction with the first primary sensing junction to determine a temperature between the first and second reference areas. Furthermore, the resistive heating element <NUM>, the first lead wire <NUM> of the second power pin <NUM>, and the third lead wire <NUM> of the first power pin <NUM> are made of the same conductive material or of materials with similar Seebeck properties, such that a voltage change created by the first junction <NUM> and the second junction <NUM> is substantially zero, and the temperature measurement determined by the controller is based on the voltage changes at the sensing junctions <NUM> and <NUM>.

The controller (not shown in <FIG>) is configured to supply power to the heating element <NUM> via the first power pin <NUM> and the second power pin <NUM>, and to measure a temperature at a virtual point between the two sensing junctions <NUM> and <NUM> based on the voltage changes created by the junctions <NUM> and <NUM>. In one form, the temperature at the first and second reference areas are presumed to be substantially the same, and thus, the temperature detected by the controller is associated with a virtual point between the first and second reference areas.

Referring to <FIG>, in one form, the primary sensing junction is provided in a cartridge heater for measuring a temperature at a virtual point outside of the heater or at a reference area within the heater. <FIG> illustrates a cartridge heater <NUM> that includes a resistive heating element <NUM> in the form of a metal wire, a first power pin <NUM>, and a second power pin <NUM>. The cartridge heater <NUM> is configured to include two sensing junctions provided outside of the heater <NUM> to measure a temperature at a virtual point between the two sensing junctions.

More particularly, in one form, the resistive heating element <NUM> is wound or disposed around a non-conductive portion (or a core in this form) as discussed with respect to <FIG>. The first power pin <NUM> comprises a first lead wire <NUM> and a second lead wire <NUM>. The first lead wire <NUM> is connected to the first end of the resistive heating element <NUM> to form a first junction <NUM>, and the second lead wire <NUM> forms a first primary sensing junction <NUM> with the first lead wire <NUM> at a first reference area outside the heater <NUM>. The second power pin <NUM> comprises a third lead wire <NUM> and a fourth lead wire <NUM>. The third lead wire <NUM> is connected to the resistive heating element <NUM> to form a second junction <NUM>. The fourth lead wire <NUM> is connected to the third lead wire <NUM> to form a second primary sensing junction <NUM> at a second reference area outside the heater <NUM>. The first and second primary sensing junctions <NUM> and <NUM> are positioned adjacent and in proximity to one another.

In one form, the resistive heating element <NUM>, the first lead wire <NUM> of the first power pin <NUM>, and the third lead wire <NUM> of the second power pin <NUM> are made of the same material or of materials having similar Seebeck properties, and are different from the material of the second lead wire <NUM> of the first power pin <NUM> and the fourth lead wire <NUM> of the second power pin <NUM>. In addition, the material of the second lead wire <NUM> of the first power pin <NUM> is different from the material of the fourth lead wire <NUM> of the second power pin <NUM>. Accordingly, the first and second primary junctions <NUM> and <NUM> operate as thermocouples to detect a temperature at a virtual point between the two junctions <NUM> and <NUM>.

<FIG> illustrates a cartridge heater <NUM> having one primary sensing junction located within the heater. The cartridge heater <NUM> includes a resistive heating element <NUM> having two ends, a first power pin <NUM>, and a second power pin <NUM>. The first power pin <NUM> forms a first junction <NUM> with a first end of the heating element <NUM> and the second power pin <NUM> forms a second junction <NUM> with a second end of the heating element <NUM>. Similar to the heater of <FIG>, the second power pin <NUM> includes a first lead wire <NUM> and a second lead wire <NUM>, which are made of different material (i.e., have different Seebeck coefficients). The first lead wire <NUM> is connected to the second end of the resistive heating element <NUM> to form the second junction <NUM>, and the second lead wire <NUM> is connected to the first lead wire <NUM> to form a primary sensing junction <NUM> at a first reference area within the heater <NUM>. Accordingly, the primary sensing junction <NUM> is operable as a thermocouple to measure a temperature at the first reference area.

In one form, the resistive heating element <NUM>, the first power pin <NUM>, and the first lead wire <NUM> of the second power pin <NUM> are made of the same conductive material or of materials having similar Seebeck properties. Accordingly, a voltage change created by the first junction <NUM> and the second junction <NUM> is substantially zero, and the temperature measurement determined by the controller is based on the voltage change created by the primary sensing junction <NUM>.

Referring to <FIG>, the primary sensing junction of the present disclosure may also be used as part of a heat flux sensor to estimate a temperature between inner surface of a heater and an outer surface of the heater. More particularly, in one form, a heater <NUM> is operable to heat a fluid (e.g., a gas) following through a tube, and comprises a resistive heating (i.e., thermal) element <NUM> (shown with phantom lines), a first power pin <NUM>, and a second power pin <NUM>. While not fully illustrated in <FIG>, the resistive heating element <NUM> is configured to extend through the heater <NUM>, and is protected by a cover. The first power pin <NUM> and the second power pin <NUM> extend into the cover of the heater <NUM> to form a first junction with a first end of the heating element <NUM> and a second junction with a second end of the heating element <NUM>, respectively.

The resistive heating element <NUM> is a "two-wire" heating element such that it functions as a heater and as a temperature sensor. Such two-wire capability is disclosed in, for example, <CIT>, which is commonly assigned with the present application and incorporated herein by reference in its entirety. Generally, for a two-wire system, the heating element <NUM> is made of a high temperature coefficient of resistance (TCR) material. A controller (not shown in <FIG>) is in communication with the first and second power pins <NUM> and <NUM>, and configured to measure voltage (i.e., mV) changes across the power pins <NUM> and <NUM>. Using the voltage change, the controller calculates an average temperature of the resistive heating element <NUM> (e.g., about R1).

The first power pin <NUM> includes a first lead wire <NUM> and a second lead wire <NUM>, which are made of different materials (i.e., have different Seebeck coefficients). The first lead wire <NUM> forms the second junction with the heating element <NUM>, and the second lead wire <NUM> forms a primary sensing junction <NUM> with the first lead wire <NUM> at a second reference area that is along an outer surface (i.e., R2) of the heater <NUM> (i.e., along a plane that is different than that of the heating element <NUM>). Accordingly, the primary sensing junction <NUM> is operable as a thermocouple to measure a temperature at the second reference area based on a voltage change created by the sensing junction <NUM>. The resistive heating element <NUM>, the second power pin <NUM>, and the first lead wire <NUM> of the first power pin <NUM> are made of the same material or made of materials having similar Seebeck properties.

In one form, the controller is configured to estimate a temperature at a virtual point between an inner surface (i.e., first reference area) and an outer surface (a second reference area) of the heater <NUM> based on the temperature measurement of the heating element <NUM>, the temperature at the primary sensing junction <NUM>, and power delivered to the heater <NUM> from the controller. More particularly, the controller determines the average temperature of the heating element at the first reference area using the voltage change across the power pins <NUM> and <NUM>, as described with respect to the two-wire system. The controller further determines the temperature at the second reference area based on the voltage change created by the primary sensing junction <NUM> and the Seebeck coefficient of the first and second lead wire <NUM> and <NUM>. Using the two measurements, the power being provided, and the heater geometry, the controller may calculate a temperature at a third reference area at a desired location in the heater <NUM> (e.g., any location within the heater). In addition, if the geometry of the heater <NUM> is known, the controller can also be configured to determine a heat flux between the inner surface and the outer surface of the heater <NUM>. The heat flux can be used to, for example, detect entry areas of cold fluid, adjust temperature set-points, and/or other suitable system controls. While the heater <NUM> is illustrated as a tube, the heater may be configured in other suitable shapes (e.g., a flat plate) and still be within the scope of the present disclosure.

Furthermore, in one form, before the heater <NUM> is energized, the heater <NUM> is substantially at room temperature, such that the primary sensing junction <NUM> is at the same or substantially the same temperature as the high TCR element wire (i.e., the heating element <NUM>). The controller is configured to measure the temperature using the primary sensing junction <NUM>, and further measure the resistance of the heating element <NUM>. The controller associates the resistance of the heater <NUM> with the temperature measured by the primary sensing junction <NUM>, and uses this baseline value to covert other resistances to a temperature, thereby calibrating the heater element <NUM>.

Referring to <FIG>, a primary sensing junction can be configured in various suitable ways to improve temperature measurement along a surface. For example, in one form, a primary sensing junction <NUM> is formed by a first lead wire <NUM> and a second lead wire <NUM> that are made of different materials. The sensing junction <NUM> has a planar shape (i.e., flat) and is surrounded by a heat diffuser <NUM> that is a thermally conductive material (e.g., copper) to improve thermal contact with the surface and to diffuse heat coming from the heating element.

The primary sensing junction of the present disclosure operates as a thermocouple to enables temperature measurements at different locations within and even, outside of the heater. Accordingly, temperature measurement is not restricted to the ends of the heating element. In addition, the heater no longer requires a discrete temperature sensor, thereby reducing the complexity of the heater.

Referring to <FIG>, a heater system <NUM> including a power control system <NUM> and a plurality of heaters <NUM>, <NUM>, <NUM>, <NUM> connected and controlled by the power control system <NUM> is shown. The power control system <NUM> includes a controller <NUM>, a wire harness <NUM>, and a plurality sets of auxiliary wires <NUM>, <NUM>, <NUM> connected to and extending from the plurality of heaters. The wire harness <NUM> and the plurality sets of auxiliary wires <NUM>, <NUM>, <NUM> connect the controller <NUM> to the plurality of heaters <NUM>, <NUM>, <NUM>, <NUM>. The plurality of heaters include a first heater <NUM>, a second heater <NUM>, a third heater <NUM>, and a fourth heater <NUM>. The wire harness <NUM> may be used to connect some or all of the plurality of heaters <NUM>, <NUM>, <NUM>, and <NUM> in series to form different modular heater assemblies or as stand-alone heaters, or a combination thereof, which will be described in more detail below. Any number of heaters may be connected by the wire harness <NUM>, and the heaters may be any type of heaters without departing from the scope of the present disclosure. The controller <NUM> is configured to supply power to the plurality of heaters <NUM>, <NUM>, <NUM>, <NUM>, determine temperatures of the plurality of heaters <NUM>, <NUM>, <NUM>, <NUM> based on temperature signals transmitted from the heaters, and control the temperatures of the plurality of heaters <NUM>, <NUM>, <NUM>, <NUM> based on the measured temperatures and target temperatures.

The wire harness <NUM> includes a plurality of connectors <NUM>, <NUM>, <NUM>, <NUM> and a plurality of electrical wires for connecting the controller <NUM> to the plurality of heaters <NUM>, <NUM>, <NUM>, <NUM>. In one form, the plurality of connectors <NUM>, <NUM>, <NUM>, <NUM> may be circular plastic connectors (CPC), which include built-in pins and sockets to allow for a wide range of power and signal transmission options, and which are structurally designed to allow for easy and quick connect/disconnect between the connectors and the electrical wires. In the illustrative example of <FIG>, the number of the plurality of connectors <NUM>, <NUM>, <NUM>, <NUM> is equal to the number of the plurality of heaters <NUM>, <NUM>, <NUM>, <NUM> such that each of the heaters is connected to another heater(s) or the controller <NUM> via a corresponding connector.

In the illustrative example of <FIG>, the plurality of electrical wires include a main power supply wire <NUM>, a main power return wire <NUM>, and a plurality of connecting wires <NUM>, <NUM>, <NUM>. The main power supply wire <NUM> and the main power return wire <NUM> are directly connected to the controller <NUM> for routing electric current to and out of the plurality of heaters <NUM>, <NUM>, <NUM>, <NUM>, respectively. The plurality of connecting wires include a first connecting wire <NUM>, a second connecting wire <NUM>, and a third connecting wire <NUM> for connecting one of the connectors <NUM>, <NUM>, <NUM>, <NUM> to another one of the connectors <NUM>, <NUM>, <NUM>, <NUM>. The plurality sets of auxiliary wires are disposed between the connectors <NUM>, <NUM>, <NUM>, <NUM> and the plurality of heaters <NUM>, <NUM>, <NUM>, <NUM>. It should be understood that three (<NUM>) connecting wires and four (<NUM>) heaters are merely exemplary and the illustrations and descriptions herein should not be construed as limiting the scope of the present disclosure. It is also understood that the plurality sets of auxiliary wires may be alternatively configured to be in the form of conductive pins without departing from the scope of the present disclosure.

Referring to <FIG>, each set of auxiliary wires for a corresponding heater includes three wires, wherein two of the three wires are made of different materials and are joined to form a thermocouple junction <NUM>, which is also joined to an end of a resistive heating element <NUM> of the heater <NUM>. More specifically, each set of auxiliary wires includes a temperature sensing wire <NUM>, an auxiliary power supply wire <NUM>, and an auxiliary power return wire <NUM>. The temperature sensing wire <NUM> is made of a first conductive material (as shown in dashed line), whereas the auxiliary power supply wire <NUM> and the auxiliary power return wire <NUM> are made of a second conductive material (as shown in solid lines) different from the first conductive material.

The temperature sensing wire <NUM> (made of the first conductive material) is joined to one of the auxiliary power supply wire <NUM> and the auxiliary power return wire <NUM> (made of the second conductive material) to form a thermocouple junction <NUM> therebetween. As shown in <FIG>, the temperature sensing wire <NUM> of each set of auxiliary wires is joined to the auxiliary power supply wire <NUM> and joined to one of a pair of terminal areas of a resistive heating element <NUM> to form a thermocouple junction <NUM> therebetween. The auxiliary power return wire <NUM> is connected to the other one of the terminal areas of the resistive heating element <NUM>. As such, electric current flows from the temperature sensing wire <NUM>, through the resistive heating element <NUM>, to the auxiliary power return wire <NUM>. The three wires may be fixed to the terminal areas of a resistive heating element <NUM> of a heater to become a part of the heater.

While three wires extend from each heater and are connected to the corresponding connector, only two of the three wires are used to carry electric current and the remaining one of the three wires is bypassed during each mode of heater operation. Which one of the three wires is bypassed depends on how the heaters are connected by the wire harness, particularly by the connectors <NUM>, <NUM>, <NUM>, <NUM> each including a first connector part and a second connector part. For example, as shown in <FIG>, the connector <NUM> includes a first connector part 614a and a second connector part 614b. All three wires are connected to a first connector part of a specific connector, but the second connector part of the specific connector connects only two of the three wires to a second connector part of another connector or the controller <NUM> via connecting wire(s), the main power supply wire, or the main power return wire. As shown in <FIG> in conjunction with <FIG>, the temperature sensing wire <NUM> and the auxiliary power return wire <NUM> for the first heater <NUM> are used to carry electric current and the auxiliary power supply wire <NUM> is bypassed. As clearly shown in <FIG>, the auxiliary power supply wires <NUM> and the auxiliary power return wires <NUM> for the other heaters <NUM>, <NUM>, <NUM> are used to carry electric current and the temperature sensing wires <NUM> are bypassed. The thermocouple junction <NUM> on the first heater <NUM> measures the temperature of the first heater, and the temperature sensing wire <NUM> and the auxiliary power return wire <NUM> for the first heater <NUM> transmit a signal relating to the temperature of the heater to the controller <NUM>.

As an example, the first conductive material may be a copper-nickel alloy such as Constantan, and the second conductive material may be a nickel-chromium alloy such as Chromel®. Any combination of first and second conductive materials suitable for forming a thermocouple junction for temperature sensing purposes may be used without departing from the scope of the present disclosure.

Referring to <FIG>, each of the connectors <NUM>, <NUM>, <NUM>, <NUM> may include a first connector part and a mating second connector part (which may be a socket and plug assembly, for example). For example, the connector <NUM> may include a first connector part 614a and a second connector part 614b. The heater <NUM> and the corresponding set of auxiliary wires (i.e., the temperature sensing wire <NUM>, the auxiliary power supply wire <NUM>, and the auxiliary power return wire <NUM>) are attached to the first connector part 614a to form a modular heater unit <NUM>. The modular heater unit <NUM> can be easily connected to other electrical components, such as another modular heater unit or the controller <NUM>, by using mating connector parts and proper connecting wires to achieve various wiring connections, all variations of which should be construed as falling within the scope of the present disclosure.

The set of auxiliary wires extending from the corresponding heater constitutes a three-wire mechanism to allow the heater to be used as both a heater and a temperature sensor. In the first modular heater assembly of <FIG>, the second, third and fourth heaters <NUM>, <NUM>, <NUM> are connected by the wire harness <NUM> in a way such that the second, third and fourth heaters <NUM>,<NUM>,<NUM> are used as heaters only to generate a desired heat output. In the second, third and fourth heaters <NUM>, <NUM>, <NUM>, the auxiliary power supply wires <NUM> and the auxiliary power return wires <NUM> are selectively used to form a part of the electric circuit, whereas the temperature sensing wires <NUM> are bypassed. The first heater <NUM> is used as both a heater and a temperature sensor by selectively using the temperature sensing wire <NUM> and the auxiliary power supply wire <NUM> to form a part of the electric circuit, and by bypassing the auxiliary power supply wire <NUM>. During the temperature sensing mode, the thermocouple junction <NUM> on the first heater <NUM> is used to measure a temperature of the heater, and the temperature sensing wire <NUM> and the auxiliary power return wire <NUM> for the first heater <NUM> and other wires in the electric circuit are used to transmit a temperature signal to the controller <NUM>.

Referring to <FIG>, an electric diagram illustrating the electric circuit of the heater system <NUM> including the power control system <NUM> and the plurality of heaters of <FIG> is shown. The plurality of heaters <NUM>, <NUM>, <NUM>, and <NUM> are connected in series in this order to form a first modular heater assembly. The main power supply wire <NUM> is made of the same first conductive material of the temperature sensing wires <NUM> as shown in dashed line. The main power return wire <NUM> and the connecting wires <NUM>, <NUM>, <NUM> are made of the same second conductive material of the auxiliary power supply wire <NUM> and the auxiliary power return wire <NUM> as shown in solid lines. As an example, the first conductive material may be Constantan, and the second conductive material may be Chromel®.

When the control system <NUM> is in the power mode, the power is supplied from CH2+ of the controller <NUM> through the main power supply wire <NUM>, the temperature sensing wire <NUM> and the auxiliary power return wire <NUM> of the first heater <NUM>, the connecting wire <NUM>, the auxiliary power supply wire <NUM> and the auxiliary power return wire <NUM> of the second heater <NUM>, the connecting wire <NUM>, the auxiliary power supply wire <NUM> and the auxiliary power return wire <NUM> of the third heater <NUM>, the connecting wire <NUM>, the auxiliary power supply wire <NUM> and the auxiliary power return wire <NUM> of the fourth heater <NUM>. The electric current returns to CH2- of the controller <NUM> through the main power return wire <NUM>.

When the control system <NUM> is in the temperature sensing mode, the electric current path is the same as that in the power supply mode. The thermocouple junction <NUM> of the first heater <NUM> is used to measure a temperature of the first heater <NUM>. The temperature of the first heater <NUM> is also the temperature of the first modular heater assembly because the first, second, third and fourth heater <NUM>,<NUM>,<NUM>,<NUM> are connected in series. The signal relating to the temperature measurement is transmitted to the controller <NUM> via the temperature sensing wire <NUM> and the auxiliary power return wire <NUM> of the first heater <NUM> and the other wires forming the circuit.

Only one of the thermocouple junctions <NUM> in the first modular heater assembly is used for temperature sensing. In the first modular heater assembly, the thermocouple junction <NUM> in the first heater <NUM> that is directly connected to the controller <NUM> by the main power supply wire <NUM> is used for temperature sensing. The main power supply wire <NUM> is made of the same first conductive material of the temperature sensing wire <NUM> and may be considered an extension of the temperature sensing wire in the first modular heater assembly.

Referring to <FIG>, a heater system <NUM> including a power control system <NUM> and a plurality of heaters <NUM>, <NUM>, <NUM>, <NUM> connected and controlled by the power control system <NUM> is shown. The power control system <NUM> includes a wire harness <NUM>', which routes the plurality of heaters <NUM>, <NUM>, <NUM>, <NUM> in a second series connection. In the following, like elements will be designated by like reference numerals and the description thereof will be omitted for clarify.

In this wiring connection, the second heater <NUM>, the first heater <NUM>, the third heater <NUM>, and the fourth heater <NUM> are connected in series in this order to form a second modular heater assembly and the power is supplied to the second heater <NUM> first. In this wiring connection, only the second heater <NUM> is used as both a heater and a temperature sensor by selectively using the temperature sensing wire <NUM> and the auxiliary power return wire <NUM> for the second heater to form a part of the electric circuit. The other heaters <NUM>, <NUM>, <NUM> are used to perform only the function of heaters by selectively using the auxiliary power supply wires <NUM> and the auxiliary power return wires <NUM> to form a part of the circuit and by bypassing the temperature sensing wires. Only the thermocouple junction <NUM> of the second heater <NUM> is used for temperature sensing of the second modular heater assembly. Like the first modular heater assembly of <FIG>, the main power supply wire <NUM> and the temperature sensing wires <NUM> are made of the first conductive material (such as Constantan), and the remaining wires are made of the second conductive material (such as Chromel®). The main power supply wire <NUM> may be considered an extension of the temperature sensing wire <NUM> for the second heater <NUM> for temperature sensing purposes.

Referring to <FIG>, a heater system <NUM> including a power control system <NUM> and a plurality of a heaters <NUM>, <NUM>, <NUM>, <NUM> connected and controlled by the power control system <NUM> is shown. The power control system <NUM> includes a wire harness <NUM>", which routes the plurality of heaters <NUM>, <NUM>, <NUM> and <NUM> in a third series connection. In this wiring connection, the third heater <NUM>, the second heater <NUM>, the first heater <NUM>, and the fourth heater <NUM> are connected in series in this order to form a third modular heater assembly and the power is supplied to the third heater <NUM> first. In this wiring connection, only the third heater <NUM> is used to perform the function of both a heater and a temperature sensor and the thermocouple junction <NUM> of the third heater <NUM> is used for temperature sensing. The other heaters <NUM>, <NUM>, <NUM> are used as heaters only by bypassing the temperature sensing wires <NUM> associated with these heaters. Similarly, the main power supply wire <NUM> and the temperature sensing wires <NUM> are made of the first conductive material (such as Constantan), and the remaining wires are made of the second conductive material (such as Chromel®). The main power supply wire <NUM> may be considered an extension of the temperature sensing wire <NUM> for the third heater <NUM> for temperature sensing purposes.

Referring to <FIG> and <FIG>, a heater system <NUM> including a power control system <NUM>' and a plurality of heaters <NUM>, <NUM>, <NUM>, <NUM> connected and controlled by the power control system <NUM> is shown. The power control system <NUM>' includes a wire harness <NUM>, which includes two sets of main power supply wires <NUM> and main power return wires <NUM> for routing one of the heaters (i.e., the fourth heater <NUM>) as a stand-alone heater, and the remaining ones of the heaters (i.e., the first, second and third heaters <NUM>, <NUM>, <NUM>) in a series connection.

The first set of main power supply and return wires connect the first heater <NUM>, the second heater <NUM>, the third heater <NUM> in series in this order to form a fourth modular heater assembly and the power is supplied from the controller <NUM> to the first heater <NUM> first. The second set of main power supply and return wires directly connect the fourth heater <NUM> to the controller <NUM> such that the fourth heater <NUM> becomes a stand-alone heater. The fourth heater <NUM> is controlled independently from the fourth modular heater assembly.

In this fourth modular heater assembly, only the first heater <NUM> is used as both a heater and a temperature sensor and the thermocouple junction <NUM> of the first heater <NUM> is used for temperature sensing. The fourth heater, which is a stand-alone heater, also functions as both a heater and a temperature sensor and the thermocouple junction <NUM> of the fourth heater is also used for measuring temperature of the fourth heater <NUM>.

Similarly, the two main power supply wires <NUM> and the temperature sensing wires <NUM> are made of the first conductive material (such as Constantan), and the remaining wires are made of the second conductive material (such as Chromel®).

Referring to <FIG>, a heater system <NUM> including a power control system <NUM>" and a plurality of heaters <NUM>, <NUM>, <NUM>, <NUM> connected and controlled by the power control system <NUM>" is shown. The power control system <NUM>" includes a plurality sets of auxiliary wires <NUM>', <NUM>', <NUM>', <NUM>, <NUM> attached to the plurality of heaters <NUM>, <NUM>, <NUM>, <NUM>, and a wire harness <NUM> for connecting the plurality sets of auxiliary wires to the controller <NUM>. The wire harness <NUM> includes two sets of main power supply wires <NUM> and main power return wires <NUM> for routing one of the heaters (e.g., the fourth heater <NUM>) as a stand-alone heater, and the remaining ones of the heaters (i.e., the first, second and third heaters <NUM>, <NUM>, <NUM>) in a series connection. The first heater <NUM>, the second heater <NUM>, and the third heater <NUM> are connected in series in this order to form a fifth modular heater assembly.

Each set of the auxiliary wires is attached to a corresponding heater and includes five wires, including a temperature sensing wire <NUM>', an auxiliary power supply wire <NUM>', an auxiliary power return wire <NUM>', a first routing wire <NUM>, and a second routing wire <NUM>. The structure and function of the temperature sensing wire <NUM>', the auxiliary power supply wire <NUM>' and the auxiliary power return wire <NUM>' are the same as that of the temperature sensing wire <NUM>, the auxiliary power supply wire <NUM>, and the auxiliary power return wire <NUM> and thus the detailed description thereof is omitted herein for clarity. The first routing wire <NUM> and the second routing wire <NUM> in each set are connected to each other and are used to help connect the first, second and third heater in a desired order. In each set of five wires, only four of the five wires in each set of auxiliary wires are used in each mode of heater operation and one of the five wires in each set is bypassed.

The first set of main power supply wire <NUM> and main power return wire <NUM> are connected to the fifth modular heater assembly. In the fifth modular heater assembly, the third heater <NUM> is the master control heater whose thermocouple junction <NUM> and temperature sensing wire <NUM> are used for temperature sensing. The third heater <NUM> functions as both a heater and a temperature sensor by selectively using the temperature sensing wire <NUM>' for the third heater <NUM> to form a part of the electric circuit. The temperature sensing wires <NUM> of the first and second heaters <NUM>, <NUM> are bypassed and the first and second heaters <NUM>,<NUM> perform the function of a heater only. The second set of main power supply wire <NUM> and the main power return wire <NUM> connect only one heater, i.e., the fourth heater <NUM>, to the controller <NUM>. The thermocouple junction <NUM> and the temperature sensing wire <NUM> of the fourth heater <NUM> are also used for measuring temperature of the fourth heater <NUM>.

Unlike the wire harness <NUM>, <NUM>', <NUM>", <NUM> in the first to fourth modular heater assembly, the wire harness <NUM> of the present form includes a plurality pairs of connectors <NUM>, <NUM>', <NUM>, <NUM>', <NUM>, <NUM>', <NUM>, <NUM>' corresponding to the plurality of heaters <NUM>, <NUM>, <NUM>, <NUM>. Each heater is connected to a pair of connectors. Moreover, the temperature sensing wire is attached to the auxiliary power return wire, not the auxiliary power supply wire, in each set of the auxiliary wires extending from the heater. Therefore, the thermocouple junction is formed between the auxiliary power return wire <NUM>' and a temperature sensing wire <NUM>' in each of the sets of auxiliary wires. The temperature sensing wires <NUM>' and the main power return wires <NUM>' are made of the first conductive material (e.g., Constantan), and the remaining wires are made of the second conductive material (e.g., Chromel®). The main power return wires <NUM>' are considered extensions of the temperature sensing wires <NUM>' for temperature sensing purposes.

Referring to <FIG>, a heater system <NUM> including a power control system <NUM>‴ and a plurality of heaters <NUM>, <NUM>, <NUM>, <NUM> connected and controlled by the power control system <NUM>‴ is shown. The power control system <NUM>'" includes a wire harness <NUM>, which includes two sets of main power supply wires <NUM> and main power return wires <NUM> for routing one of the heaters (i.e., the fourth heater <NUM>) as a stand-alone heater, and the remaining ones of the heaters (i.e., the first, second and third heaters <NUM>, <NUM>, <NUM>) in a series connection. The first, second and third heaters <NUM>, <NUM>, <NUM> are connected in series in this order to form a sixth modular heater assembly. In the sixth modular heater assembly, the second heater <NUM> is the master control heater whose thermocouple junction <NUM> and temperature sensing wire <NUM>' are used for temperature measurement and temperature signal transmission. The master control heater is disposed in the center of the sixth modular heater assembly. The first set of main power supply wire <NUM> and main power return wire <NUM> are connected to the sixth modular heater assembly. The second set of main power supply wire <NUM> and the main power return wire <NUM> connect only the fourth heater <NUM> to the controller <NUM> such that the fourth heater becomes a stand-alone heater.

Three connectors and six auxiliary wires are used for connecting the second heater <NUM> to the controller <NUM>, to the first heater <NUM>, and the third heater <NUM>. Two connectors and five auxiliary wires are used for connecting each of the first heater <NUM> and the third heater <NUM> to another heater. Two connectors and five auxiliary wires are used for connecting the fourth heater <NUM> to the controller <NUM>. Each set of the auxiliary wires for the first heater <NUM>, the third heater <NUM> and the fourth heater <NUM> includes five wires, including a temperature sensing wire <NUM>', an auxiliary power supply wire <NUM>', an auxiliary power return wire <NUM>', a first routing wire <NUM>, and a second routing wire <NUM>, similar to that of <FIG>. However, the set of auxiliary wires for the second heater <NUM>, which is used as the main control heater, includes six wires. The six wires include a temperature sensing wire <NUM>', an auxiliary power supply wire <NUM>', and four routing wires <NUM>. All of the six wires are used in each mode of heater operation.

In the present form, the thermocouple junction <NUM> for the second heater <NUM> is formed between the temperature sensing wire <NUM>' and the resistive heating element <NUM>. The thermocouple junctions <NUM> for the first and third heaters <NUM>, <NUM> are formed between the temperature sensing wires <NUM>', the auxiliary power supply wires <NUM>', and the resistive heating elements <NUM>. The thermocouple junction <NUM> for the fourth heater <NUM> is formed between the temperature sensing wire <NUM>', the auxiliary power return wire <NUM>', and the resistive heating element <NUM>. All of the temperature sensing wires <NUM>' and the two main power return wires <NUM> are made of the first conductive material (Material A, such as Constantan), whereas the remaining wires (including the two main power supply wires <NUM>, the connecting wires <NUM> connecting to the same or adjacent connectors, the auxiliary power supply wires <NUM>', the auxiliary power return wires <NUM>' and the routing wires <NUM>, <NUM>) are made of a second conductive material (Material B, such as Chromel®).

In summary, the power control system <NUM>, <NUM>', <NUM>", or <NUM>‴ constructed in accordance with the teachings of the present disclosure include a wire harness <NUM>, <NUM>', <NUM>", <NUM>, <NUM>, or <NUM> that allows the various wires to be routed via connectors to achieve various wiring connections. Some or all of a plurality of heaters may be connected in series in different orders, while the other heaters may be routed as stand-alone heaters and controlled independently from other heaters. While not shown in any of the forms, it is understood that the wire harness may include a plurality sets of main power supply wires and main power return wires corresponding to the plurality of heaters. Each set of main power supply wire and main power return wire connects only one heater to the controller such that each heater becomes a stand-alone heater and is controlled independently.

Moreover, the power control system includes a plurality sets of auxiliary wires disposed between the plurality of connectors and the heaters. The auxiliary wires may be always attached to the heaters and adjacent connector part (whether a male part or a female part) of the connectors to form a plurality of modular heater units. The plurality of modular heater units may be easily connected in series in any order or as stand-alone heaters by connecting the connector parts to another connector parts via proper wiring. Therefore, the wire harness improves modularity of the plurality of heaters.

Further, in some forms, each of the plurality sets of auxiliary wires includes three wires including a temperature sensing wire, an auxiliary power supply wire, and an auxiliary power return wire. Two of the three wires are joined to form a thermocouple junction. One of the two wires that are joined is selected to form a part of the electric circuit depending on whether the associate heater is used as a heater only or as both a heater and a temperature sensor in the electric circuit. The three-wire mechanism extending from each heater allows each heater to selectively function as both a heater and a temperature sensor, thereby eliminating the use of additional temperature sensors in the heater system and providing a heater system with a simpler design.

In other forms, the sets of auxiliary wires may include five wires or six wires. In addition to the temperature sensing wire, the auxiliary power supply wire, and the auxiliary power return wire, additional routing wires may be included in each set of auxiliary wires to increase the routing options in order to connect these heaters in different orders and to use any one of the heaters as the master control heater, which is used as both a heater and a temperature sensor.

In the figures, the direction of an arrow, as indicated by the arrowhead, generally demonstrates the flow of information (such as data or instructions) that is of interest to the illustration. For example, when element A and element B exchange a variety of information, but information transmitted from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This unidirectional arrow does not imply that no other information is transmitted from element B to element A. Further, for information sent from element A to element B, element B may send requests for, or receipt acknowledgements of, the information to element A.

In this application, the term "module" and/or "controller" may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.

The term memory is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory, tangible computer-readable medium are nonvolatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc).

The apparatuses and methods described in this application may be partially or fully implemented by a special purpose computer created by configuring a general-purpose computer to execute one or more particular functions embodied in computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications, which can be translated into the computer programs by the routine work of a skilled technician or programmer.

Unless otherwise expressly indicated herein, all numerical values indicating mechanical/thermal properties, compositional percentages, dimensions and/or tolerances, or other characteristics are to be understood as modified by the word "about" or "approximately" in describing the scope of the present disclosure. This modification is desired for various reasons including industrial practice; material, manufacturing, and assembly tolerances; and testing capability.

As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean "at least one of A, at least one of B, and at least one of C.

Claim 1:
A heater system (<NUM>) comprising:
a plurality of heaters (<NUM>, <NUM>, <NUM>, <NUM>);
a controller (<NUM>) for supplying power to the plurality of heaters
a plurality of
sets of auxiliary wires extending from the plurality of heaters;
and a wire harness (<NUM>) for connecting the plurality of sets of auxiliary wires to the controller; characterised in that the heater system further comprises
a plurality of connector parts connected to the sets of auxiliary wires, each connector part being configured to be connected to another connector part directly or via connecting wires;
wherein each set of auxiliary wires includes a temperature sensing wire (<NUM>),
an auxiliary power supply wire (<NUM>), and an auxiliary power return wire (<NUM>), wherein in each set of auxiliary wires, the temperature sensing wire is joined to one of the auxiliary power supply wire and the auxiliary power return wire to form a thermocouple junction (<NUM>), and
the material of the temperature sensing wire is different from the one of the auxiliary power supply wire and the auxiliary power return wire such that each of the plurality of heaters is operable to function as both a heater and a temperature sensor.