CN112042265B

CN112042265B - Resistive heater with temperature sensing power pin and auxiliary sensing tab

Info

Publication number: CN112042265B
Application number: CN201980029161.4A
Authority: CN
Inventors: 特里·科尔赫; 道格拉斯·舍弗尔; 杰里米·奥泽; 雅各布·伯尼亚; 埃里克·艾利斯; 路易斯·P·辛德豪尔
Original assignee: Watlow Electric Manufacturing Co
Current assignee: Watlow Electric Manufacturing Co
Priority date: 2018-04-11
Filing date: 2019-04-01
Publication date: 2023-06-20
Anticipated expiration: 2039-04-01
Also published as: KR20210007986A; JP7374922B2; CN112042265A; TW201946491A; TWI741278B; JP2021521589A; EP3777476A1; WO2019199506A1

Abstract

The present disclosure relates to a heater comprising a resistive heating element, a first power pin, and a second power pin. The first power pin forms a first junction with a first end of the resistive heating element and the second power pin forms a second junction with a second end of the resistive heating element. The second power pin comprises a first lead and a second lead. The first lead forms a second junction with the second end of the resistive heating element and defines a first conductive material. The second lead forms a primary sense joint with the first lead at the first reference region and defines a second conductive material different from the first conductive material to measure a temperature of the first reference region based on a voltage change generated by the primary sense joint.

Description

Resistive heater with temperature sensing power pin and auxiliary sensing tab

Technical Field

The present disclosure relates to resistive heaters and temperature sensing devices, such as thermocouples.

Background

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

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 is typically composed of a resistive wire heating element wrapped around a ceramic core. A typical ceramic mandrel defines two longitudinal bores in which power/terminal pins (terminals pins) are disposed. The first end of the resistive wire is electrically connected to one power pin and the other end of the resistive wire is electrically connected to the other power pin. The assembly is then inserted into a larger diameter tubular metal sheath having an open end and a closed end or both open ends, thereby forming an annular space between the sheath and the resistance wire/core assembly. An insulating material, such as magnesium oxide (MgO) or the like, is injected into the open end of the sheath to fill the annular space between the resistance wire and the inner surface of the sheath.

The open end of the sheath is sealed, for example, by using potting compound and/or a separate sealing member. The entire assembly is then compacted or compressed by swaging or other suitable process to reduce the diameter of the sheath, thereby compacting and compressing the MgO, and at least partially crushing the ceramic core to collapse the core around the pins, thereby ensuring good electrical contact and heat 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.

To determine the proper temperature at which the heater should operate, a discrete temperature sensor, such as a thermocouple, is placed on or near the heater. Adding a separate temperature sensor to the heater and its environment can be expensive and add complexity to the overall heating system.

Disclosure of Invention

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

In one form, the present disclosure is directed to a heater that includes a resistive heating element, a first power pin, and a second power pin. The first power pin forms a first junction with a first end of the resistive heating element. The second power pin comprises a first lead and a second lead. The first lead forms a second junction with the second end of the resistive heating element and defines a first conductive material. The second lead forms a main sensing joint with the first lead at the first reference area. The second lead defines a second conductive material different from the first conductive material to measure a temperature at the first reference region based on a voltage change generated by the primary sense joint.

In another form the first power pin, the first lead of the second power pin and the resistive heating element are made of the same material.

In yet another form the first and second leads are different nickel alloys.

In one form the first leads of the first and second power pins are made of the same material.

In another form, the heater further includes a controller in communication with the first power pin and the second power pin. The controller is configured to switch between a heating mode for directing power to the resistive heating element and a measurement mode for measuring a change in voltage produced by the primary sense joint to determine a temperature at the first reference zone.

In yet another form, the heater further includes a controller in communication with the first and second power pins and configured to measure a change in voltage at the first and second junctions without interrupting power to the resistive heating element.

In one form, the first power pin, the first lead of the second power pin, and the zebach coefficient (Seebeck coefficient) of the resistive heating element are substantially the same.

In another form, the primary sense connection is disposed along the resistive heating element between the first and second ends of the resistive heating element.

In yet another form, the primary sense connection is disposed external to the heater.

In one form the first power pin includes a third lead and a fourth lead. The third lead is connected to the first end of the resistive heating element to form a first joint and define a first conductive material. The fourth lead forms a second primary sense joint with the third lead at a second reference region adjacent and proximate to the first reference region. The fourth lead defines a third conductive material different from the first and second conductive materials to operate as a thermocouple and is used in conjunction with the primary sense joint to determine a temperature between the first and second reference areas.

In one form the first lead of the second power pin, the third lead of the first power pin, and the zebach coefficient of the resistive heating element are substantially the same.

In another form, the heater further comprises a heat spreader disposed about the primary sense joint.

In yet another form, the heater further includes a non-conductive portion, a jacket, and a sealing member. The non-conductive portion defines a proximal end and a distal end. The non-conductive portion has at least a first aperture and a second aperture extending through the proximal end. First and second power pins are disposed within the first and second apertures, and a resistive heating element is disposed about the non-conductive portion. The sheath surrounds the non-conductive portion, and a sealing member is disposed at a proximal portion of the non-conductive portion and extends at least partially into the sheath.

In one form, the present disclosure is directed to a heater that includes a resistive heating element, a first power pin, and a second power pin. The resistive heating element is operable in a heating mode and a measurement mode. In the measurement mode, the resistive heating element senses a temperature at a first reference zone along the resistive heating element. The first power pin forms a first junction with a first end of the resistive heating element. The second power pin comprises a first lead and a second lead. The first lead forms a second junction with the second end of the resistive heating element and defines a first conductive material. The second lead forms a main sensing joint with the first lead in the second reference area. The second lead defines a second conductive material different from the first conductive material to measure a temperature at the second reference region based on a voltage change generated by the primary sense joint.

In another form, the heater further includes a controller in communication with the first power pin and the second power pin. The controller is configured to switch between a heating mode for directing power to the resistive heating element and a measurement mode for measuring the resistance of the resistive heating element to determine a temperature at the first reference and for measuring a voltage change produced by the primary sense connection to determine a temperature at the second reference zone. The controller is configured to calculate a temperature at the third reference zone based on the temperature at the first reference zone, the second reference zone, the heater geometry, and the power delivered to the heater element.

In one form, the controller is configured to calibrate the heating element using the temperature measured by the primary sense joint.

In yet another form, the primary sense connection is formed along a different plane than the plane of the heating element.

In one form, the first power pin, the first lead of the second power pin, and the resistive heating element define one or more conductive materials having substantially the same seebeck coefficient.

In one form, the present disclosure is directed to a heater that includes a resistive heating element, a first power pin, and a second power pin. The first power pin forms a first junction with a first end of the resistive heating element. The second power pin comprises a first lead and a second lead. The first lead forms a second junction with the second end of the resistive heating element. The second lead forms a main sensing joint with the first lead at the reference area. The resistive heating element, the first power pin and the first lead are made of a first conductive material. The second lead is made of a second conductive material having a different zebach coefficient than the first conductive material to measure the temperature at the reference region based on the voltage change generated by the primary sense joint.

Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

Drawings

In order that the present disclosure may be well understood, various forms thereof will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a side cross-sectional view of a resistive heater with dual-purpose power pins constructed in accordance with the teachings of the present disclosure;

FIG. 2 is a perspective view of the resistive heater of FIG. 1 and a controller having leads constructed in accordance with the teachings of the present disclosure;

FIG. 3 is a circuit diagram illustrating a switching circuit and a measurement circuit constructed in accordance with one form of the present disclosure;

FIG. 4 is a side cross-sectional view of an alternative form of heater having multiple heating zones constructed in accordance with the teachings of the present disclosure;

FIG. 5 is a side elevational view of an alternative form of the present disclosure showing a plurality of heaters connected in sequence constructed in accordance with the teachings of the present disclosure;

FIG. 6 is a side cross-sectional view of another form of heater having a continuously variable pitch resistive element constructed in accordance with the teachings of the present disclosure;

FIG. 7 is a side cross-sectional view of another form of a heater constructed in accordance with the teachings of the present disclosure having resistive elements with different pitches in multiple heating zones;

FIG. 8 is a side cross-sectional view of a heat exchanger employing a heater constructed in accordance with the teachings of the present disclosure;

FIG. 9 is a side cross-sectional view illustrating a layered heater employing dual-purpose power pins constructed in accordance with the teachings of the present disclosure;

FIG. 10 is a flow chart illustrating a method according to the teachings of the present disclosure;

FIG. 11 is a perspective view of a heater for fluid immersion heating constructed in accordance with the teachings of the present disclosure;

FIG. 12 is a side cross-sectional view of a portion of the heater of FIG. 11 in accordance with the teachings of the present disclosure;

FIG. 13 is a graph illustrating exemplary temperature differences at various junctions of the heater of FIG. 10 in accordance with the teachings of the present disclosure;

FIG. 14 is a perspective view of another form of the present disclosure having a plurality of heater cores in a plurality of zones, constructed in accordance with the teachings of the present disclosure;

FIG. 15 illustrates a heater having a primary sense joint in accordance with the teachings of the present disclosure;

FIG. 16 illustrates a heater having two primary sense joints in accordance with the teachings of the present disclosure;

17A and 17B are perspective views of cartridge heaters with primary sense joints according to the teachings of the present disclosure;

FIG. 18 is a perspective view of a tubular heater having a primary sense connection and a dual wire heating element in accordance with the teachings of the present disclosure; and

FIG. 19 illustrates a primary sense joint with enhanced temperature measurement features in accordance with the teachings of the present disclosure.

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

Detailed Description

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

Referring to fig. 1, a heater in accordance with the teachings of the present disclosure is shown and generally indicated by reference numeral 20. This form of heater 20 is a cartridge heater, however, it should be understood that the teachings of the present disclosure may be applied to other types of heaters described in more detail below while remaining within the scope of the present disclosure. As shown, the heater 20 includes a resistive heating element 22 having two ends 24 and 26, and the resistive heating element 22 is in the form of a wire, such as a nichrome material. The resistive heating element 22 is wrapped or disposed around a non-conductive portion (or core in this form) 28. The core 28 defines a proximal end 30 and a distal end 32, and further defines a first aperture 34 and a second aperture 36 extending through at least the proximal end 30.

The heater 20 further includes a first power pin 40 made of a first conductive material and a second power pin 42 made of a second conductive material dissimilar to the first conductive material of the first power pin 40. Further, the resistive heating element 22 is made of a material that is different from the first and second electrically conductive materials of the first and second power pins 40, 42, and forms a first joint 50 with the first power pin 40 at the end 24 and a second joint 52 with the second power pin 42 at the other end 26 thereof. Because the resistive heating element 22 is a different material at the junction 50 than the first power pin 40 and a different material at the junction 52 than the second power pin 42, the thermocouple junction is effectively formed and thus the voltage changes at the first and

second junctions

50, 52 are detected (as set forth in more detail below) to determine the average temperature of the heater 20 without the use of a separate/discrete temperature sensor.

In one form, the resistive heating element 22 is a nichrome material and the first power pin 40 is

Nickel alloy, second power pin 42 is +.>

Nickel alloy. Alternatively, the first power pin 40 may be iron and the second power 42 may be constantan. It should be understood by those skilled in the art that any number and combination of different materials may be used for the resistive heating element 22, the first power pin 40, and the second power pin 42, provided that the three materials are different and that the thermocouple junctions are effectively formed at

junctions

50 and 52. The materials described herein are merely exemplary and, therefore, should not be construed as limiting the scope of the present disclosure.

In one application, the average temperature of the heater 20 may be used to detect the presence of moisture. If moisture is detected, a moisture management control algorithm may be executed by a controller (described in more detail below) to remove the moisture in a controlled manner, rather than continuing to operate the heater 20 and possibly premature failure.

As further shown, the heater 20 includes a sheath 60 surrounding the non-conductive portion 28 and a sealing member 62 disposed at the proximal end 30 of the non-conductive portion 28 and extending at least partially into the sheath 60 to complete the heater assembly. In addition, a dielectric filler material 64 is disposed between the resistive heating element 22 and the sheath 60. Various configurations and further structural and electrical details of cartridge heaters are described in more detail in U.S. patent nos. 2,831,951 and 3,970,822, commonly assigned with the present application, the contents of which are incorporated herein by reference in their entirety. Accordingly, it should be understood that the form shown herein is merely exemplary and should not be construed as limiting the scope of the present disclosure.

Referring now to fig. 2, the present disclosure also includes a controller 70 in communication with the power pins 40, 42 and configured to measure voltage changes at the first and

second junctions

50, 52. More specifically, the controller 70 measures millivolt (mV) changes at the

junctions

50, 52 and then uses these voltage changes to calculate the average temperature of the heater 20. In one form, the controller 70 measures the voltage change at the

junctions

50, 52 without interrupting power to the resistive heating element 22. This may be achieved by, for example, reading at zero crossings of the AC input power signal. In another form, power is interrupted and the controller 70 switches from the heating mode to the measurement mode to measure the change in voltage. Once the average temperature is determined, the controller 70 switches back to the heating mode, as will be described in more detail below. More specifically, in one form, a triac (triac) is used to switch power to the heater 20 and collect temperature information at or near the zero crossing of the power signal. Other forms of AC switching devices may be employed 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.

Alternatively, as shown in fig. 3, FET 72 is used as a switching device and a means of measuring voltage during the off period of the FET with DC power supply. In one form, three (3) relatively

large resistors

73, 74 and 75 are used to form a protection circuit for the measurement circuit 76. It should be understood that the switch and measurement circuit are merely exemplary and should not be construed as limiting the scope of the present disclosure.

Referring again to fig. 2, a pair of leads 80 are connected to the first power pin 40 and the second power pin 42. In one form, the leads 80 are of the same material, such as copper. Lead 80 is provided to reduce the length of power pins required to reach controller 70 while introducing another joint due to the different materials at

joints

82 and 84. In this form, in order for the controller 70 to determine which connector is measuring a voltage change,

signal lines

86 and 88 may be employed such that the controller 70 switches between

signal lines

86 and 88 to identify the connector being measured. Alternatively, the

signal lines

86 and 88 may be eliminated and the voltage changes across the

lead connections

82 and 84 may be ignored or compensated for by software in the controller 70.

Referring now to fig. 4, the teachings of the present disclosure are also applicable to a heater 20' having a plurality of

zones

90, 92, and 94. Each zone includes its own set of power pins 40', 42' and resistive heating elements 22' as described above (only one zone 90 is shown for clarity). In one form of such a multi-zone heater 20', the controller 70 (not shown) will communicate with the

ends

96, 98 and 100 of each zone to detect voltage changes and thus determine the average temperature for that particular zone. Alternatively, the controller 70 may communicate with only the end 96 to determine the average temperature of the heater 20' and whether moisture is present, as described above. Although three (3) regions are shown, it should be understood that any number of regions may be employed while remaining within the scope of the present disclosure.

Turning now to fig. 5, the teachings of the present disclosure may also be applied to a plurality of

individual heaters

100, 102, 104, 106, and 108, which may be cartridge heaters, and connected in sequence as shown. Each heater includes dissimilar power pins and first and second junctions of the resistive heating element, and thus the average temperature of each

heater

100, 102, 104, 106, and 108 may be determined by the controller 70, as described above. In another form, each of the

heaters

100, 102, 104, 106, and 108 has its own power supply pin, and a single power return pin is connected to all of the heaters to reduce the complexity of such a multiple heater embodiment. In this form of cartridge heater, each wick would include a channel that accommodates the power supply pins for each successive heater.

Referring now to fig. 6 and 7, according to another form of the present disclosure, the pitch of the resistive heating elements 110 may be varied to provide a tailored heat distribution along the heater 120. In one form (fig. 5), the resistive heating element 110 defines a continuously variable pitch along its length. More specifically, the resistive heating element 110 has a continuously variable pitch that can accommodate the pitch P on the immediately next 360 degree coil loop ₄ -P ₉ Is increased or decreased. The continuously variable pitch of the resistive heating elements 110 provides a gradual change in the flux density of the heater surface (e.g., the surface of the jacket 112). Although the principles of continuously variable spacing are shown as being applied to tubular heaters having a fill of insulating material 114, the principles may be applied to any type of heater including, but not limited to, cartridge heaters as described above. In addition, as described above, the first power pin 122 is made of a first conductive material, the second power pin 124 is made of a second conductive material that is dissimilar to the first conductive material of the first power pin 122, and the resistive heating element 110 is made of a material that is different from the first and second conductive materials of the first and second power pins 122, 124, such that voltage changes at the first and

second junctions

126, 128 are detected to determine an average temperature of the heater 120.

In another form (FIG. 7), resistive heating element 130 has a pitch P in zone A, zone B, and zone C, respectively ₁ 、P ₂ And P ₃ 。P ₃ Greater than P ₁ ，P ₁ Greater than P ₂ . The resistive heating elements 130 have a constant pitch along the length of each zone, as shown. Similarly, the first power pin 132 is made of a first conductive material, the second power pin 134 is made of a second conductive material that is dissimilar to the first conductive material of the first power pin 132, and the resistive heating element 130 is made of a material that is different from the first conductive material and the second conductive material of the first power pin 132 and the second power pin 134, such that voltage changes at the first joint 136 and the second joint 138 are detected to determine the addition Average temperature of the heater 120.

Referring to fig. 8, the heater and dual-purpose power pin described herein has a variety of applications, including, for example, a heat exchanger 140. The heat exchanger 140 may include one or more heating elements 142, and each of the heating elements 142 may also include an area or variable pitch resistive heating element as shown 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 used in any application in which heat is provided while also requiring temperature measurement, whether absolute or for another environmental condition such as the presence of moisture as described above.

As shown in fig. 9, the teachings of the present disclosure may also be applied to other types of heaters, such as layered heater 150. Generally, layered heater 150 comprises a dielectric layer 152 applied to a substrate 154, a resistive heating layer 156 applied to dielectric layer 152, and a protective layer 158 applied to resistive heating layer 156. A junction 160 is formed between one end of the trace of resistive layer 158 and a first lead 162 (only one end shown for clarity), and similarly a second junction is formed at the other end, and voltage changes at these junctions are detected to determine the average temperature of heater 150, following the principles of the present disclosure as described above. Such layered heaters are illustrated and described in more detail in U.S. patent 8,680,443, commonly assigned with the present application, the contents of which are incorporated herein by reference in their entirety.

Other types of heaters may be used in place of or in addition to the cartridge, tube, and layer heaters described above in accordance with the teachings of the present disclosure. These additional types of heaters may include, for example, polymeric heaters, flexible heaters, heat trace (heat trace), and ceramic heaters. 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. 10, a method of controlling at least one heater is shown in accordance with the teachings of the present disclosure. The method comprises the following steps:

(A) Activating a heating mode to provide power to a power supply pin made of a first conductive material and returning power through a power return pin made of a conductive material dissimilar to the first conductive material;

(B) Supplying power to the power supply pin, supplying power to a resistive heating element having two ends and made of a material different from the first and second conductive materials of the power supply pin and the power return pin, the resistive heating element forming a first joint with the power supply pin at one end and a second joint with the power return pin at the other end thereof, and further supplying power through the power return pin;

(C) Measuring the voltage change at the first and second junctions to determine an average temperature of the heater;

(D) Adjusting the power supplied to the heater as needed based on the average temperature determined in step (C); and

(E) Repeating steps (a) to (D).

In another form of the method, step (B) is interrupted when the controller switches to the measurement mode to measure the voltage change, as shown by the dotted line, and then the controller switches back to the heating mode.

Yet another form of the present disclosure is shown in fig. 11-13, wherein a heater for fluid immersion heating is shown and is generally indicated by reference numeral 200. The heater 200 includes a heating portion 202 configured to be immersed in a fluid, the heating portion 202 including a plurality of resistive heating elements 204, and at least two

non-heating portions

206, 208 adjacent the heating portion 202. Each

non-heating portion

206, 208 defines a length and includes a corresponding plurality of sets of power pins electrically connected to the plurality of heating elements 204. More specifically, each set of power pins includes a first power pin 212 made of a first conductive material and a second power pin 214 made of a second conductive material that is dissimilar to the first conductive material of the first power pin 212. The first power pin 212 is electrically connected to the second power pin 214 within the

unheated portions

206, 208 to form

joints

220, 230, and 240. As further shown, the second power pin 214 extends into the heating portion 202 and is electrically connected to a corresponding resistive heating element 204. Further, the second power pin 214 defines a cross-sectional area that is larger than the corresponding resistive heating element 204 such that no further joint or measurable heat is generated at the connection between the second power pin 214 and the resistive heating element 204.

As further shown, the terminating portion (termination portion) 250 is contiguous with the unheated portion 206, and the plurality of first power pins 212 exits the unheated portion 206 and extends into the terminating portion 250 for electrical connection to leads and a controller (not shown). Similar to the previous description, each of the resistive heating elements 204 is made of a material that is different from the first and second conductive materials of the first and second power pins 212, 214, and wherein each of the

joints

220, 230, and 240 of the first power pin 212 to the second power pin 214 are disposed at different locations along the length of the

non-heating portions

206, 208. More specifically, and by way of example, the joint 220 is at a distance L ₁ At a distance L, the joint 230 ₂ At a distance L, and the joint 240 ₃ Where it is located.

As shown in fig. 13, the temperature of

joints

220, 230, and 240 varies over time "t", joint 220 is submerged in fluid F, joint 230 is submerged in the fluid but not so deep, and joint 240 is not submerged. Thus, detecting a change in voltage at each of the

junctions

220, 230, and 240 may provide an indication of the fluid level relative to the heating portion 202. Especially when the fluid is oil in a cooking/fryer application, it is desirable that the heating portion 202 not be exposed to air during operation so as not to cause a fire. With the

fittings

220, 230, and 240 according to the teachings of the present disclosure, the controller can determine whether the liquid level is too close to the heating portion 202 and, thus, turn off the power to the heater 200.

Although three (3) joints 220, 230, and 240 are shown in this example, it should be understood that any number of joints may be employed while remaining within the scope of the present disclosure as long as the joints are not in the heating portion 202.

Referring now to fig. 14, yet another form of the present disclosure includes a plurality of heater cores 300 arranged in a zone of a heater system 270 as shown. The heater core 300 in this exemplary form is a cartridge heater as described above, however, it should be understood that other types of heaters as described herein may also be employed. Accordingly, this form of cartridge heater configuration of the present disclosure should not be construed to limit the scope of the present disclosure.

As shown, each heater core 300 includes a plurality of power pins 301, 302, 303, 304, and 305. Similar to the above-described form, the power pins are made of different conductive materials, and more specifically, the power pins 301, 304, and 305 are made of a first conductive material, and the power pins 302, 303, and 306 are made of a second conductive material that is dissimilar to the first conductive material. As further shown, at least one jumper 320 is connected between the different types of power pins, in this example, between power pin 301 and power pin 303, to obtain temperature readings near the location of jumper 320. Jumper 320 may be, for example, a lead or other conductive member sufficient to obtain a millivolt signal indicative of the temperature near the location of jumper 320, which is also in communication with controller 70, as shown and described above. Any number of jumpers 320 can be used between different types of power pins, and another location is shown at the jumper 322 between power pin 303 and power pin 305 between zone 3 and zone 4.

In this exemplary form, power pins 301, 303, and 305 are neutral legs (neutral legs) of the heater circuit between adjacent power pins 302, 304, and 306, respectively. More specifically, the heater circuit in zone 1 will have a resistive heating element (e.g., element 22 shown in fig. 1) between the power pins 301 and 302. The heater circuit in zone 2 would be located between power pins 303 and 304 with the resistive heating element located between the two power pins. Similarly, the heater circuit in zone 3 would be located between power pins 305 and 306, with a resistive heating element located between the two power pins. It should be appreciated that these heater circuits are merely exemplary and are constructed in accordance with the teachings of cartridge heaters described above and with reference to fig. 1.

Referring now to fig. 15, in one form, a heater 400 is configured to include a primary sense connection that may be disposed within the heater 400 or external to the heater 400 for measuring temperature. The heater 400 includes a resistive heating element 402, a first power pin 404, and a second power pin 406. The resistive heating element 402 has a first end and a second end. The first power pin 404 is connected to a first end of the resistive heating element 402 to form a first joint 408 and the second power pin 406 is connected to a second end of the resistive heating element 402 to form a second joint 410. The first power pin 404 and the second power pin 406 are operable to supply power to the heating element 402 via the controller.

The second power pin 406 includes a first lead 412 and a second lead 414. A first lead 412 is connected to a second end of the resistive heating element 402 to form a second joint 410, and a second lead 414 is connected to the first lead 412 to form a main sense joint 416 at a first reference zone. The second lead 414 is configured to connect the resistive heating element 402 to a controller through the first lead 412.

In one form, the first and

second leads

412, 414 are made of dissimilar conductive materials, or more specifically, materials having different zebach coefficients (Seebeck coefficient). For example, the number of the cells to be processed, can use nickel alloy iron, constantan,

Or various combinations of the like. The difference in material of the first and

second leads

412, 414 is represented in fig. 15 by different types of lines (e.g., a broken line of the second lead 414 and a dash-dot line of the first lead 412). Due to the different materials, the primary sense connection 416 is actually a thermocouple to produce a voltage change that is measured to determine the temperature of the first reference zone. Thus, in this form, the

connectors

408 and 410 for connection to the resistive heating element 402 are separate from the sensing locations. Thus, the heater 400 is not limited to detecting temperature at the ends of the heating element 402, and temperature measurements may be detected at various locations within the heater 400. Further, in one form, the first lead 412 and the second lead 414 are configured with a primary sense connection 416 external to the heater 400.

As discussed with respect to fig. 2, a controller (not shown in fig. 15) is in communication with the first power pin 404 and the second power pin 406 and is configured to supply power to the resistive heater element 402 via the power pins 404 and 406. The controller is further configured to calculate a temperature at the first reference region based on a voltage change produced by the sense joint 416 using the zebach coefficient of the material.

In one form, the resistive heating element 402, the first power pin 404, and the first lead 412 of the second power pin 406 are made of the same conductive material or materials having similar zebach characteristics (i.e., substantially the same zebach coefficient). Thus, the voltage change produced by the first and

second junctions

408, 410 is substantially zero, and the temperature measurement determined by the controller is based on the voltage change produced by the primary sense junction 416.

In another form, the resistive heating element 402, the first power pin 404, and/or the first lead 412 of the second power pin 406 are made of different conductive materials. In this configuration, the material of the second lead 414 is selected such that the zebach coefficient of the second lead 414 is least similar to the zebach coefficients of the resistive heating element 402, the first power pin 404, and the first lead 412 of the second power pin 406. Thus, the primary sense connection 416 is provided as the largest contributor to the overall temperature measurement, and any temperature measurements from the first and

second connections

408 and 410 are minimized.

As described above, the temperature may 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 measurement mode for measuring a change in voltage at the primary sense joint to determine the temperature at the reference zone.

Referring to fig. 16, in one form, the heater 420 includes two sense junctions in proximity to each other to detect a temperature at a virtual point between the two sense junctions. Here, the heater 420 includes a resistive heating element 422, a second power pin 424, and a first power pin 426. The resistive heating element 422 includes a first end and a second end. The first power pin 426 forms a first junction 428 with a first end of the heating element 422 and the second power pin 424 forms a second junction 430 with a second end of the heating element 422. The second power pin 424 is configured in a similar manner to the second power pin 406 of fig. 15, and thus includes a first lead 432 connected to the resistive heating element 422 to form a second joint 430, and a second lead 434 connected to the first lead 432 to form a first main sense joint 440 at a first reference region within the heater 420.

In this form, the first power pin 426 is configured in a similar manner as the second power pin 424 and includes two leads (i.e., a third lead 436 and a fourth lead 438) to form a sense joint. More particularly, the third wire 436 is connected to a first end of the resistive heating element 422 to form a first junction 428, and the fourth lead 438 and the third lead 436 form a second main sense junction 442 at a second reference area. The second main sense junction 442 is disposed at a second reference area of the heater 420 that is adjacent to and near the first reference area having the first main sense junction 440. Although the

sensing junctions

440 and 442 are disposed within the heater 420, the

sensing junctions

440 and 442 may also be disposed outside the heater 420.

Similar to the second power pin 424, the conductive material of the third lead 436 is different from the conductive material of the fourth lead 438 and from the conductive material of the second lead 434 of the second power pin 424. Thus, the second main sense junction 442 is actually a thermocouple used in conjunction with the first main sense junction to determine the temperature between the first and second reference zones. In addition, the resistive heating element 422, the first lead 432 of the second power pin 424, and the third lead 436 of the first power pin 426 are made of the same conductive material or a material having similar zebach characteristics such that the voltage change generated by the first junction 428 and the second junction 430 is substantially zero, and the temperature measurement determined by the controller is based on the voltage change at the

sense junctions

440 and 442.

A controller (not shown in fig. 16) is configured to supply power to the heating element 422 via the first power pin 426 and the second power pin 424, and to measure the temperature at a virtual point between the

junctions

440 and 442 based on the voltage changes produced by the two sensing

junctions

440 and 442. In one form, it is assumed that the temperatures at the first and second reference regions are substantially the same, and therefore, the temperature detected by the controller is associated with a virtual point between the first and second reference regions.

Referring to fig. 17A and 17B, in one form, a primary sense connection is provided in the cartridge heater for measuring temperature at a virtual point external to the heater or at a reference zone within the heater. Fig. 17A shows a cartridge heater 450 that includes a resistive heating element 452 in the form of a wire, a first power pin 454, and a second power pin 456. The cartridge heater 450 is configured to include two sense junctions disposed outside the heater 450 to measure the temperature at a virtual point between the two sense junctions.

More particularly, in one form, the resistive heating element 452 is wrapped or disposed about the non-conductive portion (or core of this form), as discussed with reference to fig. 1. The first power pin 454 includes a first lead 458 and a second lead 460. The first lead 458 is connected to a first end of the resistive heating element 452 to form a first joint 462, and the second lead 460 forms a first primary sense joint 464 with the first lead 458 at a first reference region external to the heater 450. The second power pin 456 includes a third lead 466 and a fourth lead 468. The third lead 466 is connected to the resistive heating element 452 to form a second junction 470. Fourth lead 468 is connected to third lead 466 to form a second main sense joint 472 at a second reference region external to heater 450. The first and second primary sense joints 464 and 472 are positioned adjacent and proximate to each other.

In one form, the resistive heating element 452, the first lead 458 of the first power pin 454, and the third lead 466 of the second power pin 456 are made of the same material or a material having similar zebach characteristics and are different from the materials of the second lead 460 of the first power pin 454 and the fourth lead 468 of the second power pin 456. In addition, the material of the second lead 460 of the first power pin 454 is different from the material of the fourth lead 468 of the second power pin 456. Thus, the first and second

main junctions

464 and 472 operate as thermocouples to detect the temperature at a virtual point between the two

junctions

464 and 472.

Fig. 17B shows cartridge heater 480 with a primary sense connection located within the heater. Cartridge heater 480 includes a resistive heating element 482 having two ends, a first power pin 484 and a second power pin 486. The first power pin 484 forms a first joint 488 with a first end of the heating element 482 and the second power pin 486 forms a second joint 490 with a second end of the heating element 482. Similar to the heater of fig. 15, the second power pin 486 includes a first lead 492 and a second lead 494 that are made of different materials (i.e., have different zebach coefficients). The first lead 492 is connected to a second end of the resistive heating element 482 to form a second joint 490, and the second lead 494 is connected to the first lead 492 to form a main sense joint 496 at a first reference region within the heater 480. Thus, the primary sensing junction 490 can operate as a thermocouple to measure the temperature of the first reference region.

In one form, the resistive heating element 482, the first power pin 484, and the first lead 492 of the second power pin 486 are made of the same conductive material or materials having similar zebach characteristics. Thus, the voltage change produced by the first joint 488 and the second joint 490 is substantially zero, and the temperature measurement determined by the controller is based on the voltage change produced by the primary sensing joint 490.

Referring to fig. 18, the primary sense joint of the present disclosure may also be used as part of a heat flux sensor to estimate the temperature between the inner surface of the heater and the outer surface of the heater. More specifically, in one form, the heater 500 is operable to heat a fluid (e.g., gas) flowing through a conduit and includes a resistive heating (i.e., thermal) element 502 (shown in phantom), a first power pin 504, and a second power pin 506. Although not fully shown in fig. 18, the resistive heating element 502 is configured to extend through the heater 500 and be protected by a cover. The first power pin 504 and the second power pin 506 extend into the cover of the heater 500 to form a first joint with a first end of the heating element 502 and a second joint with a second end of the heating element 502, respectively.

The resistive heating element 502 is a "two-wire" heating element such that it functions as a heater and a temperature sensor. Such a two-wire capability is disclosed, for example, in commonly assigned U.S. patent 7,196,295, the entire contents of which are incorporated herein by reference. Typically, for a two-wire system, the heating element 502 is made of a high Temperature Coefficient of Resistance (TCR) material. A controller (not shown in fig. 18) is in communication with the first and second power pins 504 and 506 and is configured to measure a voltage (i.e., mV) change across the power pins 504 and 506. Using the voltage variation, the controller calculates an average temperature (e.g., about R1) of the resistive heating element 502.

The first power pin 504 includes a first lead 508 and a second lead 510 that are made of different materials (i.e., have different zebeck coefficients). The first lead 508 forms a second junction with the heating element 502, and the second lead 510 forms a primary sense junction 512 with the first lead 508 at a second reference region along the outer surface (i.e., R2) of the heater 500 (i.e., along a plane different than the plane of the heating element 502). Accordingly, the primary sense connection 512 may operate as a thermocouple to measure the temperature at the second reference zone based on the voltage change produced by the sense connection 512. The resistive heating element 502, the second power pin 506, and the first lead 508 of the first power pin 504 are made of the same material or materials having similar zebach characteristics.

In one form, the controller is configured to estimate the temperature at a virtual point between the inner surface (i.e., the first reference zone) and the outer surface (the second reference zone) of the heater 500 based on the temperature measurement of the heating element 502, the temperature at the primary sense connection 512, and the power delivered from the controller to the heater 500. More particularly, the controller uses the voltage change across the power pins 506 and 504 to determine the average temperature of the heating element at the first reference zone, as described with respect to the two-wire system. The controller also determines the temperature of the second reference zone based on the voltage change produced by the primary sense connection 512 and the zebach coefficients of the first and

second leads

508, 510. Using these two measurements, the power provided, and the heater geometry, the controller may calculate the temperature at a third reference zone at a desired location in the heater 500 (e.g., any location within the heater). Additionally, if the geometry of the heater 500 is known, the controller may also be configured to determine the heat flux between the inner and outer surfaces of the heater 500. The heat flux may be used, for example, to detect an incoming zone of cold fluid, adjust a temperature set point, and/or other suitable system control. Although heater 500 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.

Further, in one form, prior to powering up the heater 500, the heater 500 is substantially at room temperature such that the primary sense connection 512 is at the same or substantially the same temperature as the high TCR element wire (i.e., the heating element 502). The controller is configured to measure temperature using the primary sense connection 512 and further measure the resistance of the heating element 502. The controller correlates the resistance of the heater 500 to the temperature measured by the primary sense connection 512 and uses the reference value to convert the other resistance to temperature to calibrate the heater element 502.

Referring to fig. 19, the primary sense connection may be configured in a variety of suitable ways to improve temperature measurement along a surface. For example, in one form, the primary sense tab 550 is formed from a first lead 552 and a second lead 554 that are made of different materials. The sense joint 550 has a planar shape (i.e., flat) and is surrounded by a heat spreader 556 of a thermally conductive material (e.g., copper) to improve thermal contact with the surface and spread heat from the heating element.

The main sensing junction of the present disclosure operates as a thermocouple to enable temperature measurements to be made at different locations within the heater, even outside the heater. Thus, the temperature measurement is not limited to the ends of the heating element. In addition, the heater no longer requires a separate temperature sensor, thereby reducing the complexity of the heater.

It should be noted that the present disclosure is not limited to the embodiments described and illustrated as examples. Various modifications have been described and many more are part of the knowledge of those skilled in the art. Any alterations of these and further modifications and technical equivalents may be added to the description and drawings without departing from the scope of this disclosure and this patent.

Claims

1. A heater, comprising:

a resistive heating element;

a first power pin forming a first joint with a first end of the resistive heating element; and

a second power pin, comprising:

a first lead forming a second joint with a second end of the resistive heating element and defining a first electrically conductive material; and

a second lead forming a primary sense joint with the first lead at a first reference region, wherein the second lead defines a second conductive material different from the first conductive material to measure a temperature at the first reference region based on a voltage change produced by the primary sense joint.

2. The heater of claim 1, wherein the first leads of the first and second power pins and the resistive heating element are made of the same material.

3. The heater of claim 1, wherein the first leads of the first and second power pins are made of the same material.

4. The heater of claim 1, further comprising a controller in communication with the first power pin and the second power pin, wherein the controller is configured to switch between a heating mode for directing power to the resistive heating element and a measurement mode for measuring a voltage change produced by the primary sense connection to determine a temperature at the first reference zone.

5. The heater of claim 4, wherein the controller is configured to calibrate the resistive heating element using a temperature measured by the primary sense joint.

6. The heater of claim 4, wherein the resistive heating element is operable to sense a temperature at a second reference zone along the resistive heating element, and the controller measures the resistance of the resistive heating element to determine the temperature at the second reference zone.

7. The heater of claim 6, wherein the controller is configured to calculate the temperature at a third reference zone based on the temperature at the first reference zone, the second reference zone, heater geometry, and power delivered to the heater element.

8. The heater of claim 1, further comprising a controller in communication with the first and second power pins and configured to measure a change in voltage at the first and second junctions without interrupting power to the resistive heating element.

9. The heater of claim 1, wherein the first leads of the first and second power pins and the resistive heating element have the same zebach coefficient.

10. The heater of claim 1, wherein the primary sense connection is disposed along the resistive heating element between the first and second ends of the resistive heating element.

11. The heater of claim 1, wherein the primary sense connection is disposed external to the heater.

12. The heater of claim 1, wherein the first power pin comprises:

a third lead connected to the first end of the resistive heating element to form the first joint, and defining the first conductive material, an

A fourth lead forming a second primary sense joint with the third lead at a second reference region adjacent to the first reference region, wherein the fourth lead defines a third conductive material different from the first and second conductive materials to operate as a thermocouple and is used in conjunction with the primary sense joint to determine a temperature between the first and second reference regions.

13. The heater of claim 12, wherein the first lead of the second power pin, the third lead of the first power pin, the zebach coefficient of the resistive heating element are the same.

14. The heater of claim 1, further comprising a heat spreader disposed about the primary sense joint.

15. The heater of claim 1, further comprising:

a non-conductive portion defining a proximal end and a distal end, the non-conductive portion having a first aperture and a second aperture extending through at least the proximal end, wherein the first power pin and the second power pin are disposed within the first aperture and the second aperture, and the resistive heating element is disposed about the non-conductive portion;

a sheath surrounding the non-conductive portion; and

a sealing member disposed at the proximal end of the non-conductive portion and extending at least partially into the sheath.