Temperature regulator

Abstract: A temperature regulator is provided which includes a temperature sensor, a temperature regulating unit (1,2,3), a cold junction temperature measuring device (10) and a first thermal insulating member (8). Temperatures measured by the temperature sensor are compensated with the temperatures measured by the cold junction temperature measuring device (10). Since the insulating member (8) insulates the device (10) from the heat generated inside the temperature regulating unit (1,2,3), the cold junction measuring device (10) can correctly measure the temperature of the cold junction.

Description: This invention relates to a temperature regulating unit according to the pre-characterizing part of claim 1. A type of temperature regulator, which employs connecting pins inserted into a socket to which a thermocouple is connected, is widely used. In such a temperature regulator, the temperature of a cold junction to which the thermocouple is connected, is measured to compensate temperatures sensed by the thermocouple. A cold junction temperature measuring device is used to measure the temperature of the cold junction. In such conventional temperature regulators, the temperature compensating device is incorporated in a boss of a connecting pin. However, since the boss is not thermally coupled to the cold junction, the temperature measuring devices cannot correctly measure the temperature of the junction. Also, since the measuring device is not thermally insulated from the heat generated inside the regulator, the operation point of the regulator often fluctuates. Furthermore, the regulator requires a long time to begin to operate stably after its power supply is turned on. A temperature regulating unit as defined in the pre-characterizing part of claim 1 has been disclosed in US-A-4,221,923. With this unit the cold junction temperature measuring device is arranged in a relatively large space within a projection adapted to be inserted into the socket. In inward direction this space is closed by the printed circuit board which does not completely insulate the cold junction temperature measuring means from heat generated inside the temperature regulating unit. It is the object of this invention to provide a temperature regulating unit in which the temperature measuring device is thermally insulated from the heat generated inside the unit in an improved manner. This object is solved by a temperature regulating unit comprising the features of claim 1. Improvements of the temperature regulating unit of the invention are characterized in the dependent claims. The above object, advantages and features of this invention will be more fully understood when considered in conjunction with the following figures, in which like numerals designate like or corresponding components and of which: Fig. 1 is a perspective view of a disassembled temperature regulating unit of a temperature regulator according to a preferred embodiment of this invention; Fig. 2 is a side view of a temperature regulating unit and a socket according to the invention; Fig. 3 is a rear view of a terminal base according to the invention; and Fig. 4 is an input circuit configuration of the temperature regulating unit including a thermocouple and a cold junction temperature measuring device according to the invention. In Figs. 1 to 3, a temperature regulating unit according to a preferred embodiment of this invention includes a front case 1 and a rear case 2. A terminal base 3 is provided on the rear side of rear case 2. The terminal base 3 includes eight pin terminals 6a-6h which are oriented, e.g., in circular configuration and are inserted into a printed circuit board 5 and a socket 4 in the orientation as shown in Fig. 2. Pin terminals 6a-6h are insert-molded into the base 3. A boss 7 is disposed at the center of the base 3. Also, base 3 includes a thermal insulating flat plate 8 having a pair of recesses 8a, and a cut-away portion 9. Either or both side surfaces of plate 8 can be corrugated. Circuit board 5 is disposed close to the insulating plate 8 in parallel with the base 3. Circuit board 5 includes a pair of cut-away portions 5a and eight through-holes 5b. Two terminals of a cold junction temperature measuring device 10, which is a temperature-sensitive resistor made, e.g., of platinum and placed in the cut-away portion 9, are mounted on cut-away portions 5a and 8a. Device 10 changes its resistance as a function of temperature. Pin terminals 6a-6h are inserted into throughholes 5b. Thus, device 10 and terminals 6a-6h are connected to circuit patterns (not shown) provided on circuit board 5. As shown in Fig. 3, four throughholes 11a-11d are disposed on the base 3 through which atmospheric air is introduced in the cut-away portion 9 in which the device 10 is positioned. A thermocouple 22 (described below and which may be positioned remote from the temperature regulating unit) is exposed to the atmosphere and functions as a temperature sensor. Device 10 measures the temperature of the atmospheric air introduced into cut-away portion 9 of base 3 to compensate the temperature measured by thermocouple 22. The terminal base 3 is fixed to the rear end of rear case 2 to complete the temperature regulating unit. In Fig. 4, a thermocouple 22 is shown connected to input terminals 20a and 20b, which are provided as cold junctions, via lines 21. The lines 21 generate a thermoelectromotive force nearly equal to that produced by the thermocouple 22, i.e., there may be some resistance losses. Resistors R1-R3 and the device 10, which has a resistance which varies as a function of the temperature near terminals 20a and 20b, constitute a bridge circuit. An operational amplifier 23 amplifies the voltage differences between its two input terminals and outputs an electric signal, the level of which corresponds to the temperature measured by the thermocouple 22. This output signal is sent to a controller (not shown) to control a process so that its temperature can reach target values. In this embodiment, the device 10 is insulated from the heat generated inside the temperature regulating unit by circuit board 5 and a thermal insulating plate 8. Consequently, device 10 is not adversely affected by this heat and can correctly detect the temperature near the cold junction.

Claims: A temperature regulating unit adapted to be inserted into a socket, comprising: a temperature sensor (22); a housing (2) having one end surface closed by a terminal base (3) formed to be inserted into said socket (4) and provided with a space (9) for housing a cold junction temperature measuring means (10) circuit-connected to a printed circuit board (5) arranged between the interior of said housing (2) and said base (3) which includes at least one through-hole (11a-11d) through which atmospheric air is introduced into contact with said cold junction temperature measuring means (10); and a compensating means (R1-R3), responsive to an output of said temperature sensor (22) and an output of said cold junction temperature measuring means (10), for compensating the temperature measured by said temperature sensor (22) with the temperature measured by said cold junction temperature measuring means (10), characterized in that said space (9) is a cut-away portion of said terminal base member (3), that a thermal insulation plate (8) is arranged between the cut-away portion (9) and said printed circuit board (5), said plate (8) being provided with recesses (8a) for passing terminal connections therethrough from said cold junction temperature measuring means (10) to said printed circuit board (5). The temperature regulating unit of claim 1, characterized in that said plate (8) has at least one corrugated surface.

Inventors: NAGANAWA KAZUTONO, SHIMONURA TOORU, TANAMURA TOSHIYA, NAGANAWA, KAZUTONO, SHIMONURA, TOORU, TANAMURA, TOSHIYA
Applicants: OMRON TATEISI ELECTRONICS CO, OMRON CORPORATION
Application year: 1988
Main classification: G05D23
IPC codes: G01K7, G05D23