JP2736344B2 - Measuring system to monitor fluid condition - Google Patents

Description

The present invention relates to a measurement and monitoring system incorporating a differential temperature sensing device, and more particularly to an improved type for detecting the presence of water in a pressure vessel such as a steam extraction tube of a steam turbine system. Such a system incorporates a split-well differential temperature sensor.

As is known, differential temperature sensors utilize thermodynamic and fluid principles to selectively sense the presence and / or onset or cessation of a liquid or gaseous material stream. U.S. Patent No. 3,366,
No. 942 (Deane) discloses an example of a known differential temperature sensor used as a flow stop detector. This sensor or probe has one heater probe connected thermally.
Consisting of a pair of thermal sensing probes, the sensing probe and the heater probe are introduced into a conduit through which material flows. The heater probe is in close proximity to one of the pair of sensing probes, and when there is no flow, the sensing probe, which is closer to the heater probe, is hotter than the other sensing probe and the fluid material is reduced. As it flows past the probe, heat is removed from the heater probe and the temperature difference between the sensing probes decreases or disappears.

U.S. Pat. No. 3,898,638 (Deane et al.) Is a differential temperature sensor whose basic structure is the same as that of the older Deane Patent 3,366,942, but with an improved internal structure of the temperature sensing probe to increase measurement accuracy. Is disclosed. As described in that patent, the selective heating of both temperature sensing probes by the heater probe is, for example, the heat distribution between the heater probe and the temperature sensing probe of the two temperature sensing probes which is located closer to the heater probe. Although achieved by a channel, convection and / or conduction in a stationary medium and conduction in a shunt also contribute to selectively transferring heat to both probes.

Another embodiment of a differential temperature sensor comprising a pair of temperature sensors and a heater element disposed in close proximity to one of them, similar to the above differential temperature sensing probe, is disclosed in US Pat. No. 4,449,403 (McQ).
ueen). The MCQueen device, due to its special use, requires the use of a large number of such sensors in the form of vertically stacked arrays in the reactor vessel guide tubes, and the output from these multiple sensors is particularly in the fuel rod area. Indicates the wet / dry state of the coolant at In such a reactor vessel, particular attention must be paid to the presence of voids, for example, voids due to steam, which cause the reactor coolant to be pushed away from the fuel rods, resulting in insufficient cooling, which tends to cause overheating. A composite device for use in sensing the properties of a coolant under three states, namely, subcooled (normal operation); saturated liquid (boiling); and saturated vapor (void), is disclosed in detail. As described in that patent, improper conditions result in a "water hammer" effect that generates pressure pulses, which can destroy important equipment such as pipes, pipe support structures, tanks and valves. is there.

U.S. Pat. No. 4,440,717 (Bevilacqua et al.) Also discloses a measurement system in which a plurality of sensors are disposed in a reactor vessel at vertically spaced intervals, each sensor providing one of a pair of thermocouple wires. It includes a heater for heating and detects the coolant level in the container by measuring not only the absolute temperature of each but also the temperature difference between them, again, the heat transfer to the liquid and the heat to the gas or vapor. The difference in heat transfer characteristics between transfer and transfer is used to sense the liquid level. Similar sensors and related systems for use in nuclear vessels or other pressurized water systems are disclosed in US Pat. No. 4,418,035 (Smith
No. 4,439,396 (Rolstad). Smith Patent No. 4,418,035 also discloses a block diagram of a multifunctional monitoring system utilizing such a sensor.

The differential temperature sensor and measurement system of the present invention has a wide range of applications, such as use in the measurement and monitoring of pressure vessels in nuclear reactor systems, as in some of the patents mentioned above, but particularly in the operation of turbine generators. And in connection with preventive maintenance. In such generators, the problems arising from the inflow of water or cold steam into the steam turbine are exacerbated as the equipment ages, especially as it is often operated periodically and / or in alternation. If the equipment malfunctions during the heat cycle, steam can flow into various places such as the main steam inlet pipe, hot reheat steam inlet pipe, low temperature reheat steam pipe, shaft outlet pipe, packing pressurized steam sealing system, turbine drain, etc. There is. Apart from structural destruction and mechanical malfunctions caused by the inflow of water or cold steam, unexpected equipment shutdowns are also serious problems.

In addition to identifying where inflows occur, the type of inflow that occurs, ie, the type of water inflow event, must be identified. For example, inflow into the turbine side pipe in the form of a water film flow can occur, often due to condensate or overspray conditions on the cold side of the pipe. They may also appear in the form of droplets or "granular" streams, and appear in the form of a continuous jet of water, varying in size, mixed with steam. A so-called slug flow may occur. That is, it is a phenomenon that a water mass clogging a part of the pipe flows down in the pipe, probably due to the discharge of water. Two-phase flow has also been observed, commonly referred to by the ambiguous definition of a "water-steam" mixture, which includes a central flow of condensed water due to the discharge of high-energy water. Finally, there is a broad category of rise in water in pipes due to condensate, spray or flow, feedwater heater tube leaks, and / or poor drainage system design. However, the majority of water inflow events are of the slow ascending type, belonging to the last-mentioned category, and are likely to appear as a precursor to other types of water inflow events. Accordingly, the measurement system of the present invention mainly relates to the last-mentioned broad category and is intended to monitor the condition in the pipe, in particular to detect the relatively slow rise of water in the pipe associated with the turbine system. And As mentioned earlier, this water source could be boiler and feedwater heaters, condensate accumulation, faulty spray equipment and ruptured pipes, accumulation due to condensate inside the turbine itself when operating in wet areas, etc. It is.

In addition to the sensors disclosed in the several patents listed above, commercially available systems have been developed which incorporate a differential temperature sensor to monitor and detect the presence of water. In other words, Solartron Tr, a company owned by Schlumberger
Solartron Protective Systems, a division of ansducers, says “Self-Validating Water Induction Monitoring Syst.
em (self-confirmed water inflow monitor system) is sold under the trademark HYDRATECT-2455D. Resistance measurements are performed in the manifold with electrodes that function to discriminate between water and steam (or air) resistance. As described in the sales document, the power supply end of the electrode is connected to the manifold body to serve as a reference electrode, which is insulated from the manifold body by a high-purity insulator. Attached to a two-port manifold of a conduit, such as a drain, for example, where each electrode detects the presence of water or steam and its output is sent to a discriminating circuit via an independent circuit. The discriminator circuit checks for component failure and indicates if there is a failure in each electrode channel, and checks the validity between the two electrode channels under the same operating conditions. The operation is based on an indication of whether a fault exists, but Solartron's HYD
The RATECT-2455D system is problematic in many respects and, in essence, cannot be expected to be reliable enough. For example,
The sensor is generally cylindrical and can be inserted and secured through the pressure vessel side wall, similar to conventional systems of this type. One segment that forms the cylindrical structure consists of an annular band of insulating material that insulates the electrode tip of the sensor from the rest of the structure. The interface between the insulating strip and the electrode and the rest of the cylindrical side wall of the sensor must be pressure-resistant sealed, for example by porcelain / metal welding. Dissimilar materials, i.e., the interface between porcelain and metal, can leak or result from the sensor structure, especially considering that the sensor structure is used in harsh environments (e.g., periodic changes in temperature or vibration). It should be very easy to break. According to experience, the useful life of such sensors is at most one to three years. Not only does this type of sensor have the durability required for an effective monitoring system, but it is also very dangerous for workers to be leaky and fragile. Also, due to its structure, the sensor cannot be repaired or replaced while the monitored system remains online.

Another example of a commercial system is Fluid Components, In
c. There is a product of the above-mentioned Patent No. 3,366,942; 3,898,638
Puff fret "Liquid Level &Inte" referring to the protection for the system disclosed in U.S. Pat. No. 4,449,403.
rface Controllers ", that is, using a sensor incorporating the probe disclosed in the above patent to measure the temperature difference. The value of the output signal depends on the medium in contact with the probe. It states that not only liquid / gas and liquid / liquid interfaces, but also wet / dry conditions can be detected, for example, a monitor circuit and a calibration circuit are shown as liquid level and interface control means that move with the sensor. Sensors and associated control means are unsuitable for use in the harsh environment of a steam turbine system, especially for providing the necessary sensing to predict water inflow. Cannot withstand the high-pressure, high-temperature conditions that appear in steam turbine systems,
The sensors are asymmetric and inherently lack the dual functions that the present invention has demonstrated to be essential for effective and reliable monitoring and control of a steam turbine system. For example, fouling tests performed by the sensor and related systems of the present invention cannot be performed by asymmetric sensors and systems incorporating the same. In addition, since it is not a double structure, it is not possible to automatically switch a failed element, for example, a heater element, while being in an online state. Also, due to the structure of the sensor, a failed heater and / or thermocouple element cannot be physically replaced while online. Also, such sensors, and thus the associated systems, will sink heat faster than water, even at low steam velocities, or cannot be used under steam flow conditions unless there is a shield surrounding the heater and thermocouple elements.

Despite incorporating technological advances, commercially available sensors and monitor / alarm systems utilizing them, as reported in the above references, have not met the pressing needs of the industry. For example, despite much attention and research since the early 1970s, the problem of water inflow in steam turbines has not yet been fully solved.

As the water inflow phenomenon becomes a serious problem, ASME (American
Society of Mechanical Engineers
The Committee on Turbine Water-Damage Prevention was established, and ANSI / ASME Standard No. TDP-1-1985 describes plant design recommendations to prevent water damage.
Recently, EPRI reported in a report CS-
Final Report “Detection of
Water Induction in Steam Turbines. Phase III: Fie
ld Demonstration. "This study shows that the demand for reliable and reliable sensors and monitoring systems that can be used in the environment of steam turbines to detect the serious problem of water inflow is becoming increasingly acute. Stressed.

Reliable detection of serious water inflow problems likely to occur in steam turbine installations, as well as detection of liquid / gas (steam) conditions and / or any changes in the high pressure and high temperature environment of the feet, such as those present in a reactor vessel The urgent need for an improved differential temperature sensor and associated monitor / alarm system to implement is still unmet. The most important consideration for a water flow monitoring system for a steam turbine is that the sensors and associated control systems are often years old until the system responds to indicate that a water flow has occurred. The fact that it remains inactive. By the way, during such a long period, it is expected that the electric elements, that is, both the heater element and the thermocouple element, periodically fail due to vibration or temperature change acting on them. Therefore, the sensor device itself must have a robust structure and sufficient mechanical strength so that it can withstand high-temperature and high-pressure conditions, its cyclic change and vibration for almost indefinite time, and provide a highly accurate and reliable output. In such a sensor, both the heater element and the temperature sensing element may fail, so that the sensor and associated monitoring / control circuit can not only be online tested, but also the heater and thermocouple elements that make up the sensor. Is also required to be able to be exchanged online.
In addition, each sensor includes a redundant or redundant component, and similarly, a cooperative control / monitor circuit automatically generates an alarm upon detecting a failure and automatically switches to a redundant or redundant element upon detecting a failure. It must be done.

A closely related problem is that the number of through holes for mounting the sensor on the side wall of the container whose condition is to be monitored must be minimized from the viewpoint of structural soundness and installation efficiency. In addition, in order to realize a necessary duplex configuration and to ensure the accuracy of the sensor output, it is a precondition that the states monitored by the respective duplex elements constituting each sensor are almost the same.

The corresponding US application filed on Jun. 5, 1987, and assigned to the assignee of the present application is U.S. Application No. 058,956 (Title of Invention:
A differential temperature sensor, which is a continuation-in-part application of the "Differential Temperature Sensor", is disclosed in U.S. Application No. 058,956, and is incorporated in the measurement and monitoring system of the present invention. Alternatively, it overcomes the other problems and disadvantages and satisfies the above object.

The sensors or detectors of the different embodiments have a uniformly robust construction and can reliably and safely penetrate the pressure vessel wall. Such penetrations to provide a given level of accuracy and verified monitoring capability to the associated metrology system can be minimized. In various embodiments, the required heater and thermocouple elements perform the desired temperature differential sensing or sensing operations, and are capable of on-line testing and on-line replacement of those elements, and are further preferred in certain preferred duplex sensor implementations. An example is that the faulty element is automatically replaced by the associated measuring system in operation. These are all basic such that a substantially cylindrical thermowell body is divided by a small gap along the bilateral plane and effectively two identical semi-cylindrical probes are sterically coupled and extend from a common cylindrical shank section. Or general structural features. In another embodiment, the body is divided into a first bilateral plane and a second bilateral plane transversely intersecting therewith to form four identical quarter-cylindrical probes. Therefore, the expression “partially cylindrical” including both of these is used as necessary. The shank is threaded on a part of its outer peripheral surface and fitted and fixed in a boss welded to the line or another pressure vessel. Alternatively, the socket can be welded and used. Partially cylindrical probes project into the interior of the line or are mounted in recesses in the boss to provide communication / sensing in connection with fluid in the line or container in either mounting method. Therefore,
Generally, a detector or sensor is attached to the pressure vessel such that its probe is in communication with the monitoring fluid in the pressure vessel. The shank is drilled from its upper free end to define a substantially cylindrical access chamber therein, which terminates in a wall at the junction of the shank and the semi-cylindrical probe.

According to a first preferred embodiment of the sensor, a central hole and a pair of holes symmetrically offset from the central hole extend in an axially parallel relationship from its bottom wall into each of the semi-cylindrical probes. Inside each semi-cylindrical probe, a heater element is inserted into a central hole and a pair of thermocouple sensor elements are inserted into a pair of symmetrically arranged holes. Thus, the sensor has a dual structure and function, each probe being heated /
The probe is selectable as a thermocouple, the heater element is powered, and the probe with the other inactive heater element constitutes an unheated thermocouple element to serve as a differential temperature sensor. As described in more detail below, the complementary elements of the two probes are alternately selected. This dual configuration offers a number of advantages, among which verification and contamination tests are performed by automatically switching the complementary set of heater elements, and complementary elements are detected when a failure is detected. There is an advantage that the monitor is automatically replaced and the monitoring can be continued irrespective of the failure of each element.

Since the shank is connected to the pipe or vessel wall, it acts as a heat sink that insulates between the heated semi-cylindrical probe and the unheated semi-cylindrical probe, increasing the accuracy of the thermocouple output. Attaching a connector box to the upper free end of the shank connects the heater and thermocouple wires to external monitoring, control and power circuits via cables. The sensor structure of the present invention allows the element to be locked in the insertion position while allowing easy access to the heater and thermocouple for replacement without having to remove the thermowell housing. .

The measurement / monitoring system of the present invention continuously checks the continuity of the heater of each sensor probe and a pair of thermocouple elements associated therewith, and appropriately determines if any of these elements is defective. Instruct. When a failed element is detected, the system automatically switches to a complementary element set to compensate for and eliminate the failed element. This ensures that the sensor can operate continuously and prevents false alarms resulting from device failure. That is, the sensor functions as the above-described differential temperature sensor.
When the two semi-cylindrical probes are represented by A and B, it is sufficient to first supply power to the heater A. Symmetrically arranged thermocouples A1, A2
One of, for example, A1 is one of the thermocouples B1, B2 of the probe B,
For example, it is used in combination with the thermocouple B1. If either thermocouple A1 or B2 fails, the system automatically switches to the respective complementary thermocouple A2, B2. Similarly, if heater A fails, the system automatically switches to heater B. Of course, the temperature difference readings (ΔT) must have the same value and opposite signs. The switching capability provided by the dual configuration of the sensors allows for automatic compensation of faulty elements without compromising continuous monitoring and without generating false alarms. Further, the heater A and the heater B are switched during the online test, and the respective outputs appearing as a result are compared, and the same value and the opposite sign Δ
By confirming that a T-indication has been formed, the system can increase the effectiveness of the test by ensuring that the sensor is not clogged with foreign matter between itself or the probes and that the calibration is still valid. Can be

The second integrated detector or sensor embodiment also uses a substantially cylindrical thermowell body with a single hole formed in each of two or four identical partial cylindrical probes. A single heater / thermometer element that can simultaneously heat the probe and measure its temperature is inserted into each hole.
The heater / thermometer element is made of nickel, iron or other similar pure metal, the electrical resistance of which varies in a substantially linear relationship with changes in temperature. For each probe involved, one heater / thermometer element is supplied with sufficient current to heat its corresponding probe and the other is supplied with a much lower current. The former serves as a heated element or probe, and the latter as a reference element or probe. The two heater / thermometer elements are connected to form corresponding branches of the bridge, and a current having a predetermined proportional relationship is sent to them to supply the heater / thermometer of the reference probe.
The same proportionality factor is multiplied by the voltage drop of the thermometer element,
The product is compared with the opposite sign to the voltage drop of the element heated by the differential amplifier. The resulting difference voltage (Δ
V) represents the value of the temperature difference (ΔT) between the selected pair of probes. (Ie, ΔT = k (ΔV) k = known constant). As in the first embodiment, a high level of differential voltage is maintained when the sensor probe is exposed to steam, and the differential voltage is substantially reduced when the probe is surrounded by water. This embodiment has the feature of a dual configuration and the switchability as described above increases the monitoring / testing capability.

According to another embodiment of the integrated sensor or detector,
Two holes are provided symmetrically in each of the two semi-cylindrical probes, and four such heater / thermometer elements are inserted into each hole. Therefore, two pairs of heaters and a reference element are provided,
Each pair constitutes one element with each of the two semi-cylindrical probes. Preferably, the holes are arranged symmetrically in each probe, and two sets of substantially diagonal elements are each associated as two pairs. Therefore, this embodiment also has the feature of the double structure, and the switching capability described above increases the effectiveness of the monitor / test operation, and enables automatic repair or replacement when a device fails.

According to yet another embodiment of the integrated sensor and detector, a cylindrical thermowell body is divided into four small gaps along two mutually perpendicular left and right symmetry planes, preferably intersecting along its axis. The same semi-cylindrical probe is formed. This embodiment has the same duplex configuration,
With the same switching capability and parallel independent operation capability as described above, two monitor states of ΔT output can be selected. By associating the four elements as before, ie as two corresponding pairs, the redundant high temperature differential output from both pairs improves the ability to reliably detect and indicate the absence of steam, ie, water. Similarly, the redundant low temperature difference output increases the reliability of detecting the presence of water.
On the other hand, if each pair indicates opposing high temperature difference and low temperature difference outputs, this may indicate sensor failure or sensor contamination.

Integral sensors or detectors not only allow for enhanced and diversified sensing capabilities in increasingly complex configurations, but also have the additional advantages of reduced size and reduced manufacturing and installation costs, and more importantly. This means that thermal performance and mechanical strength are also improved.

The measurement and monitoring system incorporating the integrated sensor functions in the same manner as the first system embodiment described above, but has a simple internal configuration, simplifies and reduces wiring for interconnection, and is manufactured and manufactured. Installation and maintenance costs are further reduced.

The sensor and associated monitoring system of the present invention will be described in further detail with reference to the accompanying drawings.

FIG. 1 is an elevational view showing a casing 10 of the split tubular thermowell sensor of the present invention, which will be described with reference to the bottom view and the top view shown in FIGS. Sensor housing 10
Is preferably formed by machining a cylindrical rod made of metal such as stainless steel having excellent mechanical strength but low thermal conductivity as shown in the figure. One end of the bar is machined to form two identical substantially semi-cylindrical sensor probes 12A, 12B, and the two sensor probes 12A, 12B are separated by cutting the boundary 13 thereof. Probe 12
The ends or tips 14A, 14B of A, 12B are further machined to form chamfers 15A, 15B. Therefore, probe 12
The opposite ends or bases of A and 12B are integrally protruded from the shank portion 20 of the sensor housing 10, and a collar 18 having a diameter slightly larger than the outer circumference of the probes 12A and 12B is substantially displaced from the shank 20 and the sensor 12A for the purpose described later. , 12B. Pipe threads are formed in the portion 22 of the shank 20 so that the housing 10 can be mounted in a known manner on a corresponding threaded boss that is welded to the steam pipe. An annular mounting projection 24 is formed on the outer surface of the upper free end of the shank 20, and threaded holes 26, 27 are formed in the annular end surface 28 of the shank 20 for purposes described below.

By drilling from the upper free end of the shank 20, it passes coaxially through most of the entire length of the shank 20, and the probes 12A, 1
A substantially cylindrical chamber 30 is formed that reaches the bottom wall 32 near the proximal joint of 2B. Center holes 34A, 34B are formed in the probes 12A, 12B, respectively, from the bottom wall 32 in an axially parallel relationship to the positions near the tips 14A, 14B. The holes 34A and 34B are for accommodating an elongated cylindrical heater element (not shown in FIGS. 1 to 3) as described later. Holes 36A1, 36A2 and 36 symmetrically arranged with holes 34A and 34B interposed therebetween, respectively.
B1 and 36B2 each have a length that is approximately two-thirds of the axial length of probes 12A and 12B, and accommodate corresponding thermocouple elements (not shown in FIGS. 1-3).

The sensor housing 10 has a total axial length of about 15 cm, a maximum diameter of about 5 cm, and the threaded portion 22 corresponds to a standard 3.8 cm pipe tap formed on the boss for mounting the housing 10 as described above. . Slot 13 separating sensor probe 12A, 12B
The width of the probe may be about 3 mm, and the outer diameter of the probes 12A and 12B is about 6 mm.
mm is fine. Holes 34A and 34B of the heater element have a diameter of 6.6 mm,
The depth measured from the bottom wall 32 is set to 7 cm, and the holes 36A1, 36A2 and 36B1, 36B2 of the thermocouple element have a diameter of 3.5 mm and a depth of 5 cm.
Should be set to. Each of these holes is further cut to form countersinks of slightly larger diameter and about 0.7 cm deep. These countersinks are given the same reference numerals 34A ', 34B', 34A1 '... 34B'2 as the corresponding holes, but with a dash.

FIG. 4 is a cross-sectional view of the sensor housing 10 in a cutaway plane along line 4-4 of FIG. 5, showing a complete assembly of sensors. A protective shield 40 having a hole 42 in the cylindrical side wall 43 and often also having a hole in the bottom 44 is attached to the sensor probe 12A, 1A.
2B, the upper free end of which is secured to the collar 18 of the shank 20 of the sensor housing 10 by a weld bead 46.
The primary function of the shield 40 is to reduce the vapor flow rate around the sensor barrel or probe and still allow water to flow. The high vapor flow rate cools the heated sensor probe as effectively as water. Thus, by providing holes 42 symmetrically in shield 40, a minimum or limited flow can be in direct contact with the sensor probe when the sensor is positioned in the flow path, i.e., defined inside shield 40. Contact within the sensor chamber. Hole
Although 42 is symmetric with respect to the probes 12A and 12B, it is not necessarily arranged evenly around the cylindrical side wall 43 of the shield 40, but is arranged so as to coincide with the flow direction. Must be correctly oriented. The holes may be provided at the base of the shield.

Extension assembly 50 connects electrical connector box 60 to housing 10
Removably attached to the upper free end of the. The lower end of the assembly 50 is telescopically fitted to the annular projection 24 of the housing 10 and is welded to the upper end of the bottom wall 61 of the box 60 as shown by a weld bead 52. In FIG. 4, for easy understanding, 4-4 in FIG.
A notched plane along the line is shown. The extension assembly 50 includes two elongated tubes 53A, 53B which, as can be seen in FIG. The lower end fits into 34B ',
Each upper end reaches the same height as the upper surface of the bottom wall 61 of the connector box 60. Similar to the tubes 53A, 53B,
However, smaller diameter tubes 53A1, 53A2 and 53B1, 53
B2 has its lower end corresponding to countersunk holes 36A1 ', 36A2' and 36B
1 'and 36B2', and extend to the upper surface of the bottom wall 61 of the connector box 60 in the same manner as the tubes 53A and 53B. The bottom wall 61 includes a central hole 62 for receiving the various tubes described above.

In the connector box 60, a plate 63 is arranged so as to overlap with and close the hole 62. A threaded rod 64 is screwed into the screw hole 26 of the sensor housing 10, while projecting upward from the hole 65 of the plate 63, a nut 66 is screwed into the screw 63, and the plate 63 is further screwed through the plate 63. .Box 60 and extension assembly 50
Is fixed to the sensor housing 10. Holes 66A and 66B are formed in the plate 63 (not shown) for conducting wires to the heater element, and holes 67A1, 67A2 and 67B1 and 67B2 corresponding to the four thermocouples accommodated in the sensor housing 10 are formed. Formed on the plate 63. FIG. 4 shows the thermocouple 70 inserted through the plate 63 with its upper end cut away. A true arc ring 72 is fitted around the upper end of the thermocouple 70 and engages with the lower surface of the plate 63 to fix the thermocouple 70. Spring-type snap rings 74A, 74B are fitted into slots formed in the side walls of the corresponding tubes 53A, 53B (not shown in FIGS. 4 and 5) to secure the heater element in the corresponding holes 53A, 53B. doing. The terminal plate 80 is attached to the bottom plate 61 by screws and nuts 82A and 82B.
A, 80B fixed, 6 probes for each probe half
A sufficient number of terminal screws 84A, 84B to connect to the lead wires from the respective thermocouples and heaters 12A, 12B are attached to each terminal plate 80.
A, 80B.

As shown in FIGS. 4, 5 and 6, the cover plate 85 has four hanging surfaces 87, covers the upwardly bent end 61a of the bottom plate 61, and is fixed by a self-tapping screw 88. Engagement holes 89, 66b are provided for inserting cables (not shown) used for connecting the terminal plates 80A, 80B to the connection screws 84A, 84B.

FIG. 7 shows a heater element 90 used in the sensor of the present invention, which comprises a substantially cylindrical heater element portion 91 having a lead wire 93 extending from a grooved tip 92. As shown in FIGS. 4 and 5, a clip 74 for fixing the heater element 90 is fitted to the grooved portion 92. Preferred commercially available heater elements include Watlow Com, St. Louis, Mo.
There is a FIREROD CARTRIDGE HEATER (codename EIA51) for the manufacture of pany, diameter 6mm, length 7.5cm, 120 volts, 80
Watts.

FIG. 8 is a plan view of a thermocouple 95 that can be used in the present invention, which comprises an elongated, generally cylindrical body and a conductor 96. Preferred commercial thermocouples that can be used include those manufactured by the Marlin Manufacturing Company, Cleveland, Ohio
Model CAIN-18U-10RP is available.
It has a length of about 25 cm suitable for accommodation in the sensor housing 10 and the extension assembly 50 shown in the figure.

The sensor 10 has a dual and rugged configuration, which has the advantages of low manufacturing and installation costs, as well as easy replacement and maintenance of problematic or failed components online. The system and related circuits of the present invention using these dual sensors are described with reference to FIGS. 9, 10, 11A-11C.

FIG. 9 is a block diagram of a measurement and monitoring system for a plurality of sensors as shown in FIGS. 1 through 8 of the present invention. FIG. 9 shows two sensors, namely
Although only sensor I and sensor II are shown, the system typically includes a greater number of sensors. Since the configuration of each sensor is the same, the dual internal elements of the probe are only schematically illustrated for sensor I. As shown by the same reference numerals as in FIGS. 1 to 8, each of the sensors I is a heater (HTR).
A, a dual probe A, B consisting of a heater (HTR) B, thermocouples (TC) A1, A2, and thermocouples (TC) B1, B2. Similarly, processor I corresponding to sensor I includes a heater control circuit 100 and a thermocouple control circuit 102, each of which connects to system controller 104 via bidirectional buses I (HC) and I (TC). Device 104 also includes a plurality of bidirectional buses II.
Multiple processors via (HC),… and II (TC),…
And the corresponding control circuit (HC
And TC), and also to a central display and an operator control panel 108 via a bidirectional bus 106. As will be described in detail later, under control of the system controller 104, the heater control circuit 100 performs calibration, on-line test (for example, electrical conduction check and ground short-circuit), alarm instruction processing, and switching of the heaters A and B of the sensor I. . Similarly,
Under the control of the system controller 104, the thermocouple control circuit 102 performs similar functions for each of the thermocouples A1, A2 and B1, B2, such as an on-line test and automatic switching at the time of element failure.

FIG. 10 is a block diagram partially illustrating details of the measurement and monitoring system of the present invention for a single processor I (ie, the processor shown in FIG. 9) including a heater control circuit 100 and a TC control circuit 102. As shown, the respective interface circuits in the control circuits 100 and 102
Reference numerals 118 and 129 connect the internal components of these control circuits to the system controller 104. The heater elements HTR A and HTR B are each independently checked for continuity, current, and calibration (“CCCFC
C ") is connected to an adjustable power supply 116 via a device 110 and a switching selection circuit (SELECTOR) 112. The display device 114 is connected to a heater element HT.
It includes alarm lamps 116 and 118 respectively corresponding to RA and HTR B, and each of which is independently turned on by a corresponding output from the device 110 when a failure occurs in the corresponding heater element. The cooperating devices 110 and 114, the device 112 and the adjustable DC power supply 116 are connected to the system controller 104 via the interface circuit 118 and the corresponding bus as shown.

The system controller 104 automatically adjusts the output of the DC power supply 116 according to the state detected by the CCCFCC device 110 and the selection of the heater element HTR A or HTR B performed by operating the selector 112 by the system controller 104. By doing so, the heat outputs from the heaters A and B are made equal. The device 104 also displays a heater fault on the central display panel 108, as described below.

The sensor in Fig. 10 has four thermocouples (TC) A1, A2, B1, B2
Including, as in the conventional configuration of the differential temperature sensor,
One thermocouple of probe A is associated with the corresponding thermocouple of probe B and connected in series in a bucking or reverse relationship. That is, as shown, thermocouple elements TC A1 and TC B1 are connected as a cooperating pair, thermocouple elements TC A2 and TC B2 are connected as a second or complementary pair, and the two pairs are connected. Are represented by TCP-1 and TCP-2, respectively. Continuity check device 1
21 intermittently checks the continuity of each pair of thermocouples. If the continuity is abnormal and an element failure is detected, an output is sent to the TC failure alarm device 120 to output the faulty thermocouple TCP-1.
Alternatively, the alarm lamp 120-1 or 120-2 corresponding to TCP-2 is turned on, and the output is sent to the system controller 104 to display a failure on the central display panel 108 as described later.

The selector device 122 supplies two TC TEMP CIRs to supply one of the outputs ΔT1 and ΔT2 to the interface circuit 129.
CUIT 124-1 and 124-2 are controlled to select either output. TC TEMP CIRCUIT 124-1, 124-
One of the two outputs a voltage signal STEMP proportional to the temperature difference (ΔT) sensed by the selected thermocouple. The interface circuit 129 connects the devices 121, 122, 124-1 and 124-2 to the system controller 104 via corresponding buses as shown. The device 104 also selectively displays ΔT on the central display 108 during normal monitor operation, displays a failed sensor and a failed heater / thermometer pair, and automatically displays the alarm status of each sensor on the central display 108. And after verification.

11A, 11B and 11C show the arrangement of various displays and control modules of the display and operator control panel 108 of FIGS. The 11A readout and control module 130 includes a digital display 132 that indicates the value and sign of the temperature difference ΔT (ΔF) measured by a given sensor and selected to display as described below.

Under the control of switch 140 by the operator, the system can be set to an automatic test mode, indicated by the lighting of lamp 138, or to a selective test mode, indicated by the lighting of lamp 139, in which the operator can As described in detail below, any one of the plurality of sensors can be tested. The instantaneous actuation of switch 142 provides a "test all sensors" or "test single sensor" operating mode, as described below. The digital display unit 132 can be operated only by the operator, and displays ΔT of an arbitrary sensor. The "failure sensor" lamp 135 and the "failure heater or TC (thermocouple) lamp" 136 indicate corresponding alarms, described in more detail below. By pressing switch 137, all indicator lights of the system can be tested.

FIG. 11B shows the extraction monitor 150. Since a number of such monitors are used in a typical turbine system, a plate 152 is provided to identify the particular function being monitored, and thus the location of the associated sensor. The sensors are located at corresponding alarm lamps 155, 156, 157 and 160 on the extraction tube associated with the turbine, as shown schematically on the monitor panel 150. Specifically, the alarm lamp 15
5 corresponds to a sensor located on the turbine side of the separation valve 158,
Alarm lamp 156 corresponds to the sensor located between isolation valve 158 and check valve 159, alarm lamp 157 corresponds to the sensor located in the lower part of the extraction pipe, and alarm lamp 160 corresponds to the high level at the heater. Corresponds to a sensor located in the heater to detect the water level condition. When water is detected by a given sensor, the corresponding alarm lamp on monitor panel 150 is automatically turned on.

Since many different types of monitors can be incorporated into the system, a corresponding monitor display and control panel incorporating alarm lamps similar to the monitor panel 150 would be provided. One example is the water monitor panel 170 shown in FIG. 11C, which includes alarms 1001 to 1004. Thus, although the present invention includes different types of monitors each having a corresponding monitor display and control panel, the same number of monitors required for each type, the extraction monitor panel 150 shown in FIG. Is considered below as a representative example.

The sensor of the present invention simplifies the operation of the system, making monitoring and verification capabilities more meaningful. In connection with the sensor I schematically shown in FIG.
Suppose A is selected and selector 122 selects a pair of thermocouples TCP-1 consisting of thermocouples TC A1 and TC B1. Under normal operating conditions (hence, in the absence of water surrounding the dual probes A and B of sensor I) TC A1 is HTR A
To generate a positive ΔT output STEMP with respect to a reference polarity or direction with each output as a pair. Conversely, if complementary heater B is selected, powered, and substituted for heater A, then under this same analysis condition, the STEMP output will be negative ΔT, ie, while the numerical or absolute temperature difference values will be the same. The signs are reversed. As already mentioned,
The calibration circuit of the device 110 is operated under the instruction of the system controller 104,
In addition, the same heater output is generated in HTR A and HTR B by controlling the power level supplied to the heaters A and B through the adjustment of the adjustable DC power supply 116. If the sensors are not clogged, the absolute value is the same ΔT To occur.

The system of the present invention uses heater B in place of heater A in the event of heater A failure (or vice versa) to ensure continuous monitoring and avoid false alarms that would otherwise result from heater failure. Therefore, by switching between the heater A and the heater B, the advantage of the dual sensor is exhibited.

In conjunction with the TC control circuit 102 shown in FIG. 10, the dual configuration of the sensors also significantly enhances the capabilities of systems that include thermocouples. That is, if the continuity check circuit 121 detects that one or both of the thermocouple elements of the TCP-1 has a failure, the selector 1 is controlled by the system controller 104.
22 automatically switches to the second pair of TCP-2 and TC TEMP circuit 12
The output is supplied to 4-2, and the value STEMP (ΔT) is obtained from the circuit. As shown in FIG. 10, the pair RCP-2 is a thermocouple TC A1 and
It is connected in the same direction as the complementary first pair TCP-1 consisting of TC B1. Therefore, the complementary pair of heater elements HTR A and HTR B
When TCP-2 is selected, the same ΔT is formed. Not surprisingly, TC A2 and TC B2, ie, against RCP-2
If the direction of TCP is reversed with respect to TCP-1, a more complicated configuration having a greater failure indication capability can be obtained. Thus, for example, when using a given heater, such as an HTR A, the first
Pair TCP-1 has failed and the system automatically
If it switches to CP-2 and the sensor operates otherwise, a negative ΔT, ie a temperature difference output of the same value but of opposite sign, is generated. This simplifies maintenance because it indicates which thermocouple has failed.

Physical replacement (as distinguished from automatic switching) of the heater and thermocouple elements that make up the sensor can be performed online after the faulty element is identified by the processor I, which can be located remotely from the control panel 108. . In the drawing, the HTR and TC failure alarm display units 114 and 120 are incorporated in the heater control circuit 100 and the TC control circuit 102, respectively, but the display units 114 and 120 may be arranged in a place where maintenance personnel can easily see. When a failed element is detected, an alarm lamp 116 or 11 corresponding to heater A or heater B is used.
8, or the alarm lamp 120-1 or 120-2 corresponding to the thermocouple TCP-1 or TCP-2, respectively, is turned on.

Both heaters A and B and / or both thermocouples TC
If P-1 and TCP-2 fail, this sensor channel becomes inoperable, preventing false alarms. Also, the flashing of the lamp 136 (FIG. 11A) and the alarm lamp corresponding to the failed channel indicate to the user that this channel has failed and is inoperable. Automatic switching is performed to verify the sensed alarm. Specifically, as the water level rises and probes A and B are immersed, the normal ΔT value drops significantly below the alarm threshold, but to a value that is not normally zero. Therefore, by switching the heaters and comparing the corresponding ΔT values of STEMP, the alarm condition can be automatically verified. If the signs are the same, but the numbers are different, it can be concluded that a fouling of sensor I and a decrease in the ΔT value is a false alarm. On the other hand, if the sensor does not pass this verification test, the operator has been warned that system maintenance is required.

The system operation displayed and controlled on the control display / operator control panel 108 will be described based on the above background.

First, consider a normal operating state. In “automatic” or “select” test mode, the operator
By pressing the corresponding alarm lamp / switch on 150, eg, alarm lamp / switch 155, the ΔT of each sensor in the system can be determined. alarm·
A delay circuit triggered by actuation of a lamp / switch, eg, 155, maintains the ΔT display on display 132 of module 130 for a predetermined time, eg, two minutes. Monitor panel 15
0 or any other alarm on the monitor panel
The activation of the lamp / switch, eg 156, resets the delay circuit.

As already mentioned, these same alarm lamps / switches are illuminated when the corresponding sensor senses an alarm condition. As also mentioned above, the system performs an automatic verification test on the sensor channel indicating the alarm condition by switching the heater prior to the alarm indication in the automatic test mode selected by switch 140. However, switching for verification is not performed for a sensor in which one of the heaters has failed. The switching function is performed in one of three different forms: one "automatic test" mode and one of two manual or operator controlled modes, as described below.

Specifically, when switch 140 is set to the automatic test mode position to light lamp 138, system controller 104 responds to an alarm condition detected by a given sensor to perform a verification test on that sensor. Perform the switching function (however, as already mentioned, this sensor
This is the case if the switching test is not blocked by a heater failure in the channel, in which case an alarm is triggered based only on the single heater that is functioning of the sensor). An alarm is triggered if a ΔT occurs with the same numerical value but opposite sign (thus both absolute values are below the alarm threshold). If the difference between the two ΔT values is larger than a predetermined value, for example, 3 ° F., the erroneous sensor
An alarm is issued. This alarm is cleared by switching switch 140 to the center neutral position or Selective Test Mode (139). In a preferred embodiment of the system of the present invention, in "automatic test mode":
The switching test is performed according to predetermined criteria only for the sensor channel indicating the alarm. In the automatic test mode, the switching test is performed only for one cycle in response to the alarm instruction. Furthermore, when the switch 140 returns from the neutral or "selective test mode" position to the "automatic test mode" position, any channels indicating an alarm are switch tested before another alarm is generated.

A second type of switching test switches switch 140 to the "selective test mode" position (thus igniting lamp 139) and at the same time switches 142 to a single sensor.
The operator can select by instantly pressing the test position (143) and instantly pressing the alarm lamp / switch corresponding to the desired channel, for example, the alarm lamp / switch 155 on the monitor panel 150. Next, ΔT of the switched sensor is displayed on the display unit 132 of the monitor 130. As already mentioned, the delay circuit changes this indication to 2
Hold for minutes or until another switch prompting the display is pressed.

A third type of switching test is performed on all channels simultaneously by switching switch 140 to position 139 and momentarily pressing switch 142 to the "all sensor test" position (lighting lamp 144). This causes all sensors to switch from heater A to heater B (or from B to A if the initial direction is reversed). Two minutes later, the operator manually turns on the alarm lamps / switches one by one (for example, 155, 156, 157, ... for the monitor panel 150).
By manually pressing, the corresponding ΔT is sequentially displayed on the display unit 132 of the module 130. The ΔT readings of the series of sensor channels are compared to the previously recorded ΔT of the same channel before all heaters were switched.

In either of these two manual test modes, the operator is asked if an actual alarm condition exists.
That is, whether the ΔT display is the same absolute value ΔT below the predetermined threshold value (although the sign is reversed), or whether the sensor is clogged, that is, the numerical value varies depending on the switching position.
Can be verified.

Other checks can be made in the manual switching test. For example, as already mentioned, if one heater of a given sensor (eg, sensor I) fails,
The switching test is blocked and no ΔT change is observed in any of the manual test modes. This identifies the sensor in which one heater has failed. Display 114
And 120 lamps identify the particular failed heater and failed thermocouple, respectively.

The fault sensor is identified by the flashing of the fault sensor lamp 135 and the alarm lamp / switch corresponding to the sensor channel, for example, the alarm lamp / switch 155 of the control panel 150. The failed sensors are: (1) Both thermocouples TCP-1 and TCP of a given sensor detected by device 121;
(2) failure of both heater elements A, B of a given sensor detected by device 110; and (3) confirmation of sensor failure by switching test in "automatic test mode" described above. Either result is indicated by device 104.

By pressing button 137 on module 130,
All lamps on the control display / operator control panel 108 (FIG. 10), ie, individual modules, eg, 130, 152, 170
All lamps can be tested, including the specific indicators (FIGS. 11A-11C) and alarm lamps.

FIG. 12A is a perspective view of a divided cylindrical housing 210 showing the external configuration of the second and third embodiments of the sensor. The internal configuration of the second and third embodiments is different as described later. The external configuration of the sensor 210 is substantially the same as that of the housing 10 of FIG. Due to the small number of elements, reduction in material costs, simplification of electronic circuits, and reduction in manufacturing and mounting costs are attempted. For example, the sensor housing 10 of FIG. 1 can be configured to fit the size of a 1.5 inch nipple pipe screw, but the sensor housing 210 can be configured to fit an element having a 1 inch nipple pipe screw. You may comprise.

The housing 10 of FIG. 1 and the public, housing 210 of FIG. 12A have a single substantially anti-cylindrical probe 212A, 212B that
Separated by gaps 213 defined by bilateral symmetry planes about the axis of 210. The housing 210 has a shank 220 similar to that of FIG. 1 and on its outer periphery formed a pipe thread 222 or other means for attaching the housing to a pipe or other pressure vessel via a suitable boss. Have been. The shank 220 is further perforated to define a substantially cylindrical chamber (not shown in FIG. 12A) that substantially corresponds to the chamber 30 having the bottom wall 32 of the housing 10 of FIG.

FIG.12B shows a probe 212A in a plane perpendicular to the axis of the housing 210,
FIG. 2B is a cross-sectional view taken along line 212B of FIG.
And holes 224A and 224B that are located substantially symmetrically in the center of and extend in an axially parallel relationship to positions near the free ends 214A and 214B of the respective probes. According to this embodiment of the invention, an integrated heater / thermometer element having substantially the same external shape and dimensions as heater element 95 of FIG.
Inserted into 4B. These holes have a diameter of 6.5 mm (0.2 inch) and a depth of 6 mm for sensor 10 of FIG.
3.5 mm (2.5 inches). Such a heater element is 12B
Although not shown in the figure, their locations are indicated by respective holes 224A, 22
H / TA and H / TB in parentheses adjacent to 4B.

Elements H / TA and H / TB are heater elements made of nickel, iron or other similar pure metals, and exhibit a substantially linear or conventional relationship of electrical resistance to temperature. 14th through
As described below with reference to FIG. 16, one element, for example, H /
TA not only as a heater but also as a thermometer at the same time
Thus, a sufficient level of current is provided to act as a heated element. The other element H / TB is supplied with a much lower current, which is virtually negligible as a heater element but acts as a thermometer and thus as a reference element. In this example,
Probe 212A is the probe to be heated, and probe 21A
2B is a reference probe. As will be understood from the description of the first embodiment of the present invention, if steam and water are present alternatively, a high temperature difference signal and a low temperature difference signal are generated as outputs of a specific sensor element pair, respectively, as described later. I do.

FIG. 12C is a cross-sectional view of the probe 212A, 212B cut along a plane transverse to the axis of the housing 210. Third of the present invention
In the embodiment, the internal configuration of the housing 210 has the same four holes,
That is, the holes 224A1 and 224A2 of the probe 212A 'and the probe 212B'
Holes 224B1 and 224B2, and each hole has the same dimensions as in the above-described example and each probe 212
A 'and 212B' are symmetrically arranged at equal distances from the side walls. Four heaters / thermometer H / T in these holes
(Elements A1, A2, B1, B2) are inserted. In the example of FIG. 12C, a complete duplex configuration is obtained like the sensor 10 of the first embodiment of the present invention shown in FIGS. H instead of system
Necessary design changes can be made according to the configuration of the integrated heater / thermometer of the / T element. Systems specifically designed to utilize the integrated sensor of FIG. 12 and the integrated sensor of the fourth embodiment described below are described in FIGS.
Shown in the figure.

FIG. 13A is a perspective view of a sensor housing 310 of a fourth embodiment substantially corresponding to the housing 210 of FIG. 12A, in this case having four partial cylindrical gauges (ie, four symmetrical cylinders). The substantially quarter-cylindrical probes 312A1 to 312B2 are separated by gaps 313-1 and 313-2 defined by intersecting bilateral symmetry planes in a mutually perpendicular relationship symmetrically to the axis of the housing 310.
As shown in the cross-sectional view of FIG. 13B, using the same notation as in FIG. 12C, holes 323A1 and 324A2 have respective probes 312A1 and 312A.
A2 is formed in each probe 312B1,3
Formed at 12B2, these corresponding heater-thermometer elements are inserted into respective holes. With a sensor having an enclosure 310, the associated diagonal heater / thermometer element pairs (ie, H / T A1 and H / T B1, and B1 pairs and H / T A2 and H
/ T B2 pair) can operate as two completely independent differential temperature sensors.

The sensor of FIGS. 12A to 13B further includes an electrical connector box and associated circuitry as described in the first embodiment but which has a simplified configuration due to the reduced number of electrical components and the associated circuit connections required thereby. A structure may be provided.

FIG. 14 is a circuit for energizing a selected one of the associated heater / thermometer (H / T) elements A and B, as well as extracting a difference voltage representing the sensed temperature difference from their respective voltage outputs. Is schematically shown. This figure is 12B
The example of a single pair of related elements H / TA, H / TB as used in the housing 210 having the internal configuration as shown in the figure is shown, but the diagonal relation is shown for each configuration in FIGS. 12C and 13B. It can be understood that each pair of H / T elements can be similarly connected. Further, a single such related H, typically of the configuration of FIG.
Although the / T pair is selected at a time for such circuit connection and operation, it is also possible to connect both such pairs of the configuration of FIG. 13B to such a circuit so as to perform sensing simultaneously.

The operation of the circuit of FIG. 14 will be described with reference to FIGS. In FIG. 14, constant current sources 97 'and 94' for supplying currents I0 and I0 ÷ 50, respectively, are connected in series with elements H / TA and H / TB corresponding to the first and second branches of the bridge circuit. Connected, the two branches are interconnected in parallel with a first set of opposite connection points in the vertical direction in the drawing. The external circuit connected between these nodes will therefore have a current of 51 / 50I0
carry. Voltage output at a second set of nodes in the horizontal direction
V _a and V _b is' supplied to the input of the voltage V _b is engaged over the proportional coefficient (x50) by the circuit 94 ". Proportionality factor current source 97 'differential amplifier 98 two minutes and by 94' since the inverse of the difference current supplied through the branch, the voltage output V _a and V _b
It is possible to compare, circuit 94 'is thus generates an output 50 V _b to be sent to the second input of the differential amplifier 98'.
Thus, the difference between the temperature difference between the voltage output of the differential amplifier 98 ', V = Va-50V b, is sensed by the element H / TA and H / TB,
That is, it represents T = k (ΔV). Δ from differential amplifier 98 '
The V output is applied to a trigger / alarm circuit 99, which generates an output indicative of a vapor (normal) or water (alarm) sensing condition, which may be the actual ΔT value, respectively.

The complementary function of the circuits 94 'and 94 "allows the heater element H /
The temperature sensing function of TB is equivalent to element H / TA. However, although H / TA also functions as a heated element, H / T
H / TB serves as a reference element because B of B is not substantially heated, ie, its heating is insignificant.

The thermal function of the pair of H / T elements of the integrated sensors 210, 310 will be described using the following definitions of temperature and temperature difference.

T (H ₂ O) - the temperature T of the steam or water pipes or vessel (IWDEI / vapor) - the temperature difference between the probe 212A, the surface of the 212B and steam, which is usually 60 ° F.

T (IWTI / water)-the temperature difference between the surface of the probes 212A, 212B and water, which is 0 ° F.

T (metal)-the temperature difference across the metal (e.g., 224A) of the probe (212A) to be heated, which is assumed to be small and zero.

T (IWDI-H / T)-the temperature difference across the (air) gap between the inner surface of the hole 224A of the probe 212A and the heated element, H / TA, which is typically 20 ° F.

The changes in the sensed temperatures (T _a and T _b ) of H / TA and H / TB in steam and water, respectively, are shown in FIG. The differential amplifier 98 'in FIG. 13 subtracts out T (H ₂ O) common to H / TA and H / TB by subtraction. T (IWDI-H / T) depends only on the power dissipated in H / TA when the hole H / T gap is less than or equal to 10 mils. The power level supplied to the H / TA (ie,
Current I0) and the power supplied to the H / TB (ie, the current I0
(50) is kept substantially constant by the current sources 97 'and 94', so that T (IWDI-H / T) is substantially constant.

The temperature of H / TA in the steam is therefore T _a = T (H ₂ O) + T (IWDI−steam) + T (IWDI−H /
T) For water, _Ta is:

_{T A = T (H 2 O} ) + T (IWDI-H / T) T Temperature of H / TB in among steam and water _b = T (H ₂ O) Therefore, the temperature difference in the vapor T = T _a - _{T b = k (V a -50V} b) = T (IWDI-sTEAM) + T (IWDI-H / T) in the water T = T (IWDI-H / T) which changes T, then typically in the steam T = 80 ゜ F
To T = 20 ° F. in water.

FIG. 16 shows the above-mentioned typical temperature difference ΔT, 80 ° F. in the case of steam and the temperature difference 20 in the case where water is present and detected.
5 is a temperature diagram showing a temperature change of ゜ F and a typical 60 ゜ F between these temperature differences. FIG. 16 shows that ΔT
= Trigger level of 35 ° F, which is the range of temperature difference between the temperature difference in the presence of steam and water and a value set slightly lower to determine the alarm condition of the presence of water It is. In the configuration of FIG.
The alarm circuit 99 automatically discriminates between a steam (normal) state and a water (alarm) state and uses a voltage threshold value corresponding to ΔT = 35 ° F. as a trigger level for generating an output representing any of the states. I can do it.

The sensor 310 of FIGS. 13A and 13B is shown in FIG.
Since it has the same function as the configuration of FIGS.
It can act as a fully duplex sensor as described in connection with the figures. In fact, the sensor 310 also functions as two independent and separate differential temperature sensors, so that the state detected by logically combining the respective temperature difference indications from two separate H / T element pairs. It provides a selection function and thus can have a self-verification function. Four
If only the indications A1, A2, B1, and B2 are used for simplicity of description as H / T elements, A1-B1 vs. A2-B2 vs. detection status indication High ΔT High ΔT Normal High ΔT Low ΔT Failure Low ΔT High ΔT Fault Low ΔT Low ΔT Alarm 12C and 13 when each relevant H / T pair is selected
The operation of the embodiment of FIG. B is likewise fully described by equations (1) through (5) above, with the typical temperature difference specified in the definition being particularly pronounced in the configuration of FIG. 13B. Assuming that the probe here is formed in a housing 310 corresponding to the housing 210 except for the size and material, there is a slight difference that the weight and wall thickness of each probe are slightly different due to small weight.

FIGS. 17 and 18 show a control system such as a display and operator control panel using the integral dual-partitioned cylindrical sensor of the second to fourth embodiments and its related components. As previously mentioned, the embodiment of FIG. 12B has dual switching capability, while the embodiment of FIG. 12C allows for automatic switching of elements with dual configuration and redundancy, and the first to eighth embodiments. It is functionally the same as the first embodiment of the figure. On the other hand, 13A and 1
The embodiment of FIG. 3B has yet another capability as long as it can essentially function as two independent differential temperature sensors or detectors. Referring first to FIG. 17, a plurality of integrated sensors, 1,
,... 48 are respectively connected to channels 410 with corresponding reference numbers of the sensor control device 400, and each channel 410 is controlled by the system control device 400 and the display / operator control panel 404. Each channel device of the sensor controller 400 has alarm lamp switches 401 and 403, which are the failed H / T A1-B1 pair and the failed H / T
The status of each A2-B2 pair is displayed to facilitate identification of the failed pair, thereby simplifying maintenance. H / T for a given sensor
If both pairs fail, the channel is deactivated accordingly, and an indication to that effect is made on the panel 404 described above.

The display / operator control panel 404 has a number of modules that correspond substantially to the modules 130, 152 and 170 of FIGS. 11A-11c, with the major exception that the readout control module 130 of FIG.
The difference is that there is a display of the failed H / T element instead of the display of the failed heater or TC related to 136. In this regard, since the integrated sensors of the third and fourth embodiments have the same function as the differential temperature sensing function of the first embodiment, all of the latter operating functions are essentially as described above. It can be seen that it can be realized with the same manual and / or automatic control device. The system control device 402 shown in FIG.
Interfacing with 04, 9th, 10th and 11A-1
As explained earlier for the monitor system in Figure 1C,
The H / T pairs of the individual channels of the sensor controller 400 are selected automatically or in response to control inputs manually selected by the operator on the display / operator control panel 404.

FIG. 18 shows a single sensor control channel 410, for example, FIG.
4 shows a control circuit of channel No. 1 of the sensor control device 400 shown in FIG. Because the integrated sensor has a duplicated configuration, a single such channel controller 410 has two identical sub-channels, "H / T vs. A1-B1 sub-channel 410, as shown in FIG.
-1 "and" H / T vs. A2-B2 subchannel 410-2 ". Since subchannels 410-1 and 410-2 are identical, only the A1-B1 subchannel is shown in detail. Controller 410 has two associated subchannels 4
Either 10-1 or 410-2 is selected to control these operations, and directly interfaces with the system controller 402 in FIG. 18 in a manner to be described later.

The current select switch 412 controls the I0 current source 414 and I0 ÷ 50 under control of the channel controller 410 via leads 418 and 420.
The current source 416 is selectively connected to the H / T elements H1 and B1. H /
T temperature select switch 422 is connected to H / via lines 424 and 426.
Receives voltage level signals from T A1 and H / T B1 and
Under the control of the sensor channel controller 410 via 8 and 420, these signals are processed in the manner described below.

More specifically, when the control signal on line 418 is high (418 'is low), H / T element pair A1-B1 is selected and activated, while H / T element pair A2-B2 is in standby. It is in. Conversely, when the line 418 'is high and the line 418 is low, the H / T element pair A
2-B2, that is, the sub-channel 410-2 is selected and activated. When the signal on the line 420 goes high, the switch 412 sends the current I0 from the current source 414 to the H / T element A1 and I0 ÷ 50.
A current is supplied from the current source 416K to the H / T element B1. Line 420
When the signal is low, the reverse connection is made. Therefore, the channel controller 410 will set H / T when 418 is high.
The element pair H-B1 can be selectively switched between the element to be heated and the reference element. The signal on line 420 'plays the same role for H / T A2-B2 of subchannel 410-2.
Typically, the sensor channel controller 410 will normally select a given pair of elements, eg, H / T A1-B1 (ie, line 418 is high) and element A1 (when line 420 is high). H / T B1 or H in the active state that carries I0 and carries the opposite selection in response to input sent from system controller 402 (FIG. 18) via input lines 471 and 474. Switches to / TA2-B2. Lines 418 'and 4
When the signal at 20 'is high (when it is high) (418 and 420 are low), switch 410 has current source 41
6 'supplies I0 ÷ 50 current to H / T elements A2 and B2.

Is H / T element pair A1-B1 by the high level signal on line 418 is selected and the element A1 is assumed to be carrying a I ₀ (line 420 also high level), the line 42 is the temperature selection switch 420
The high and low voltage outputs of H / T element pair A1-B1 received via 4 and 426 are provided on output lines 428 and 430, respectively. These outputs are each multiplied by x1 (ie 1x)
And x50 (ie, 50 times) are processed by multiplier circuits 432 and 434, which are operational amplifiers. The outputs on lines 436 and 438, respectively, are sized for comparison by differential amplifier 440, except when a temperature difference is detected by H / T elements A1-B1. These circuit operations correspond to the circuit operations described with reference to Fig. 14, and the multiplication circuit 434 and the differential amplifier 440 correspond to the elements 94 "and 98 'in Fig. 14. The temperature selection switch 422 is of course H. / T A1-B1
Are provided according to their selection as reference and heating element. For example, if line 420 is low, the output voltage of H / T B1 on line 426 is greater than that on line 424, so switch 422 switches the former output to output line 428 and the latter to output line 430. To. Thus, the amplifier 434 always has I ₀ ÷ 50 to the reference probe H / T element.
It receives the output voltage of the element of the reference probe determined by the supply of current.

The output of the differential amplifier 440 is therefore a signal representing the temperature difference ΔT (ΔT = kV) sensed by the H / T element pair A1-B1. The output ΔT is further supplied to a switch 442 via a line 440, and the switch 442 is connected to a control line.
The output of the corresponding sub-channel 410-1 or 410-2, which is activated by the sensor channel controller 410 via the 444 and is currently selected and activated, is selected by the input line 474 to the controller 410 to the channel output line 446. And provides the .DELTA.T signal on that line to the system controller 402 and display-operator control panel 404 in accordance with FIG.

The sensor channel controller 410 simultaneously performs error checking and verification on the operating channel and the resulting ΔT output state, and the operation of all four H / T elements of the associated integrated sensor and their supporting circuits. Monitor and verify status.

The error checking and channel capability verification operations take into account the normal range of voltage levels in both the active and standby states of the H / T element pairs of both subchannels. First of all, it is essentially open circuited, taking into account the most typical source of error, namely the disconnection of the leads or the burnout and failure of the heater element as expected from the schematic diagram of FIG. . The characteristics of the low current source 97 'and 94', corresponding bridge output voltage V _a or V _b corresponding to each of the H / T element and / or the support circuitry in open state, A _a or A _b
Approaches the so-called "rail voltage" of the current sources 97 'and 94', i.e. the highest voltage reached by the current sources in an attempt to maintain a constant current state. 14 with reference to FIG, rail voltage, for example molecules of the bridge receiving the I ₀ V _a output 150 volts I ₀
The _Vb output of the molecule undergoing ÷ 50 is 12 volts. On the other hand, V _a
Has a typical operating voltage range of 50 to 125 volts and _Vb of 1 to 2.5 volts. Conversely, one or the output voltage V _a and V _b both are short-circuited in the H / T element becomes zero volts or a value close thereto. Therefore, the operation range of the output voltage V _a can be defined as a range over the upper limit threshold voltage of 125 volts from the lower limit threshold voltage of 25 volts. Similarly, for the output voltage _Vb , its operating range can be defined as a range from a lower threshold voltage of approximately 0.5 volts to an upper threshold voltage of 2.5 volts. However, as described above, the output voltage V _b of the lower level are normalized with respect to the voltage V _a by FIG. 18 (x50) circuits 434 and 462. Therefore, comparators 450 and 4 in FIG.
The reference voltages V _REF1 and V _REF2 sent to 52 are both H / T elements A1
And the operating range of the output voltage of B1 are 25
And the lower and upper limits of 125 volts.

H / T element pair A1-B1 is active, and line 4
The signal on 20 is at high level and element A1 is at high level current I ₀
Temperature switch 420
Provides not only the output voltage of element A1 on line 428 but also the same output voltage on line 464 to comparator 450. The low level output of element B1, supplied with I ₀ I50 current, is applied as before to multiplier 434 via line 430, and the multiplied output is sent to comparator 452 via line 439. .
Thus, the voltages on lines 464 and 434 are both V _REF1 and V _REF
It should be within the range determined by _REF2 (ie, _25-125 volts). If neither is the case, the corresponding comparator 450 or 452 generates an error signal on the respective outputs 451 and 453. OR gate 454 sends such an error signal output to controller 410 via line 458. Element A1 and
When B1 is switched, each output flows through the opposite circuit with the same result.

If the signal on line 418 is low, the element pair A1-B1 is not selected and is thus in a standby state. Element A1
And B1 are both switched from the current source 416 by the switch 412 to I ₀ ÷ 50.
Because the current is supplied, each voltage output should be at the same low level. In this situation, switch 42
2 connects the output voltage on line 424 to line 428 and line 4
Send the output on 26 onto line 430. Input 460 is selected for temperature select switch 422 in this example, the signal on line 436 is received via line 437 and x50 multiplier 462, and the resulting multiplied signal on line 464 is referenced to reference V _REF1. Sent to comparator 450 for comparison with. The output voltage on line 430 from switch 422, at a value in its normal range, is H / T A1−
When B1 is selected, it matches the output voltage of the unheated element of the reference probe. Thus, as before, its output voltage is multiplied by X50 multiplier 434 and applied to comparator 452 via line 435. The same lower and upper threshold voltages and their ranges sent by V _REF1 and V _{REF2 remain} applicable to determining the operability of the H / T elements A1 and B1 in the standby state.

Thus, the operating and supporting circuit of the H / T elements A1 and B1, for example, whether the element pair A1-B1 is in the operating state or in the standby state, and irrespective of the state of the element A2-B2 It can be seen that an error signal is generated on line 458 if the current sources 414 and 416, switches 412, 422, etc. fail. The sensor channel controller 410 sends a corresponding error signal via the output line 470 to the system controller 402 (FIG. 18).
To indicate the failure of a given sub-channel H / T pair (eg, sub-channel 410-1 element pair H / T A1-B1 and sub-channel 410-2 element pair H / T A2-B2). . Similarly, if both sub-channels of a given channel are faulty, an error signal is sent via output line 472 to indicate that the entire sensor channel has failed. In addition, the sensor channel controller 410
A standby state is detected in response to a signal requesting switching of the H / T element pair control signal received via the line 474 from the system controller 402 internally or detecting a failure of the element pair of one subchannel. Switching to one sub-channel is performed. Of course, if both sub-channels are in a fault condition, operator intervention is required.

As described above, the sub-channel 410-2 is substantially the same as the sub-channel 410-1, so that the same signal is transmitted through the same operation and corresponding signal line as shown by the same reference numeral and reference numeral in FIG. receive. The error checking function between the two sub-channels 410-1 and 410-2 is also continuously performed.

Thus, the system of FIG. 18 is similar to the monitor system of FIGS.
1 and 410-2 and the H / T element pair are fully operational in the automatic and operator control modes described above to provide the same status indication signal. However, the integrated sensors provide easier interconnection and signal processing compared to known systems, improving reliability, mounting,
Similar flexibility and reliability are provided to the monitoring and verification functions as well as a reduction in maintenance and operating costs.

In conclusion, the monitoring system of the present invention automatically verifies the alarm condition of a given sensor generated by a first normally selected pair of active elements by a switching test using a complementary second heater element. In addition to continuous on-line testing and automatic detection of element failures, appropriate fault signals are generated, and supplementary elements are automatically replaced to constantly monitor and diagnose all sensor positions. If necessary, an alarm is issued immediately, and a false alarm due to a failure of a component is avoided. In addition to automatic and continuous on-line tests, a selective test mode under operator control is provided. Critical to these capabilities of the system is the duplex configuration and switching capabilities of the sensors of the present invention.
The sensor not only has a rugged configuration that guarantees a long service life, but also has the ability to replace failed heaters and sensor elements online, and redundant and redundant sensors provide full functionality through automatic replacement of complementary elements. maintain. While various modifications and adaptations of the sensor and measurement system of the present invention will be apparent to those skilled in the art, it is to be understood that the appended claims include all such claims.

[Brief description of the drawings]

FIG. 1 is an elevation view showing a thermowell housing of the sensor of the present invention. FIG. 2 is a bottom view of the split tubular thermowell housing of FIG. FIG. 3 is a top view of the split tubular thermowell housing of FIG. FIG. 4 is a cross-sectional view of the sensor assembly of the present invention including the electrical connector box and related structures in a plane passing through the axis of the split tubular thermowell housing of the present invention shown in FIG. FIG. 5 is a sectional view taken along a line 5-5 in FIG.
It is a top view shown by a partial cross section. FIG. 6 is an end view showing the cover element of the connector box shown in section in FIGS. 7 and 8 are plan views respectively showing a heater and a thermocouple element used for the sensor of the present invention. FIG. 9 is a block diagram schematically showing a monitor system using a plurality of split cylindrical sensors of the present invention. FIG. 10 is a simplified block diagram partially showing the relationship between the measurement / monitoring system of the present invention and each element of the divided cylindrical sensor. 11A, 11B and 11C are plan views showing components of the display / operator control panel of the system of the present invention. FIG. 12A is a simplified perspective view of a split tubular thermowell housing, which is substantially the same as that of FIG. 1, but differs in internal configuration according to the second and third sensor embodiments. Having. FIG. 12B is a cross-sectional view of the probe portion of the sensor housing of FIG. 12A taken on a plane transverse to the central axis of the sensor housing, showing the internal configuration of the second sensor embodiment. FIG. 12C is a cross-sectional view of the sensor housing of the sensor housing of FIG. 12A taken along a plane transverse to the central axis of the sensor housing and showing the internal configuration of a third sensor embodiment. . FIG. 13A is a simplified schematic diagram of a thermowell housing of a fourth sensor embodiment comprising four symmetrical partial cylindrical probes defined by crossed bilateral symmetry planes. FIG. 13B is a cross-sectional view of the probe of the thermowell housing of FIG. 13A in a plane transverse to the central axis of the housing. FIG. 14 energizes the heater / thermometer element pair of the integrated sensor of the embodiment of the present invention shown in FIGS. 12A-13B and senses a difference voltage indicative of the difference between the temperatures sensed by the pair. FIG. 1 is a simple circuit diagram showing a current source and a bridge circuit configuration for the present invention. FIG. 15 is a temperature diagram illustrating the temperature levels sensed by a heater / thermometer element pair and the corresponding differential voltage generated by the pair according to an embodiment of the integrated sensor. FIG. 16 is a temperature diagram for explaining the setting of a trigger level for discriminating the differential voltage output of the circuit of FIG. 14 representing steam and water, respectively. FIG. 17 is a schematic block diagram showing a monitor system according to a second embodiment using a plurality of the integral type split cylindrical sensors of the second to fourth embodiments. FIG. 18 is a schematic block diagram showing a part of the measurement and monitoring system of FIG. 10 is a housing, 12A and 12B are sensor probes, 13 is a slot,
14A, 14B is the tip, 15A, 15B is the chamfer, 18 is the color,
20 is a shank part, 22 is a threaded part, 28 is an annular end face,
30 is a chamber, 50 is an extension assembly, 51 is a cylindrical sleeve,
60 is a connector box, 62 is a center hole, 63 is a mounting plate, 6
4 and 65 are fixing means, 70 and 95 are thermocouples, 74 is a clip, 86
Is a cover plate, 87 is a hanging side wall, 89 is an alignment hole, 90 is a heater element, and 93 and 96 are conducting wires.

Claims (22)

(57) [Claims] 1. A measurement system for monitoring the condition of a fluid in a pressure vessel containing steam and a variable amount of water, the system comprising at least two bodies in use which are in communication with the fluid in the pressure vessel. At least one dual differential temperature sensor comprising a pair of identical temperature measuring probes and two probes including a complementary set of heaters and temperature sensing elements, each of the complementary sets being provided with a given pair of probes. In cooperation, when energized, they are selectively activated to heat one probe of the given pair, thus configuring a given pair of associated heating reference probes, and Sensing the temperature of the associated heating reference probe and generating a corresponding sensed temperature output indicative of the temperature difference therebetween.
A temperature difference having a high and a low value, respectively, in response to a pair of associated heating reference probes of the sensor being exposed to either of the vapor and water conditions in the pressure vessel, wherein the at least two identical temperature measurement probes Are thermally isolated from each other, and further include selective energizing means for selectively energizing a given heater element of a complementary set of heaters and temperature sensing elements of a given sensor; Means for measuring a temperature difference between one of the sensed temperature outputs to generate a corresponding sensed temperature difference output, and operating during a normal monitor mode to select one of the complementing sets as an operating set, Control means for keeping the other of the two complementary sets in a standby state, wherein the control means controls the selective biasing means to activate the selected set and controls the measuring means to sense the temperature of the selected set. Find the difference between outputs and output the corresponding sensed temperature difference output Continuation system, characterized in that the raw. 2. The apparatus of claim 2, further comprising means for sensing the temperature sensing of any complement of a given sensor and determining failure of any of the heater elements to generate a corresponding failed element output, wherein said control means is responsive to the selected operating set. In the normal monitor mode, the fault determining means selects the other one of the complementary sets in the standby state in response to the output of the faulty element as the operating set, controls the selection biasing means and controls the determining means, and thus is selected. The measuring device according to claim 1, wherein a difference between the other set of sensed temperature outputs is determined. 3. The system according to claim 2, further comprising sensor display means for displaying the failed element in response to the failed element output.
The measuring device according to the paragraph. 4. A method according to claim 1, further comprising exposing the associated pair of sensor probes of the sensed temperature output of the measuring means generated in response to the given set of sensed temperature outputs to the vapor and water conditions in the pressure vessel. Means for determining a value of the reference temperature difference between the relatively high and relatively low values, and a value of the sensed temperature difference output of the measuring means generated in response to the sensed temperature output of the selected operating set. The apparatus of claim 1 further comprising: means for generating an alarm output when the sensed temperature difference output is less than or equal to the reference temperature difference value as compared to the difference value. 5. The control means activates the measuring means by selecting an element of the complementary set in a standby state in response to an alarm output of the comparing means in the verification mode and controlling the urging means. Apparatus according to claim 4, wherein the difference between the sensed temperature output of the selected complement set and the corresponding complemented value temperature difference output is generated. 6. A comparison between a sensed temperature difference output of the measuring means generated when the monitor mode is selected for a given sensor and a sensed temperature difference output of the measuring means when the verification mode is set as a result of an alarm output. Device according to claim (5), verifying the alarm condition. 7. The apparatus according to claim 6, further comprising means for displaying an alarm in response to the alarm output.
The device according to item. 8. The system of claim 1, further comprising: means for detecting a temperature sensing and a failure of any of the heating elements of a given sensor of the complementary set to generate a corresponding failed element output, wherein the control means is in a normal monitor mode during the on-line test. Selectively operable, the other complementary set in the standby state is selected as the operating set, and the selective energizing means is controlled to energize the measuring means;
The apparatus according to claim 1, wherein the difference between the sensed temperature outputs of the other complementary set selected in this way is determined. 9. A system comprising a plurality of differential temperature sensors, respective biasing means and measuring means, the control means comprising a system control means and a plurality of sensor control means respectively associated with the plurality of sensors, and the system control means comprising a plurality of sensor control means. The apparatus according to claim (8), wherein the on-line test of each associated sensor is performed by controlling the sensor control means. 10. The apparatus according to claim 1, further comprising means for comparing the temperature difference outputs generated by each of the plurality of measuring means in the normal monitor mode and in the on-line test, and performing operation tests of the corresponding sensors. Apparatus according to claim (9). 11. A system display means for displaying, for each of a plurality of sensors, a temperature difference output during a normal monitor mode and an on-line test of each of a plurality of measuring means associated with each sensor. Apparatus according to claim (10). 12. The system display means displays the temperature difference output for only one selected set of single sensors, and the system control means comprises a plurality of sensor control means and a separate sensor control means for each of the monitor mode and the on-line test mode. Correspondingly, the respective sensors and the respective measuring means are selected one after the other to determine the respective temperature differences corresponding to the selected set of sensors in the monitor mode and the complementary set during the online test. Apparatus according to claim (11), characterized in that the output is sent to the system display means and displayed one after another together with the display of the selected sensor. 13. The system display means comprising a plurality of alarm display means each corresponding to a plurality of sensors, each of said corresponding alarm sensor display means supporting an alarm state of an associated sensor. The device according to (11). 14. A means for determining the failure of any of the complementary set of temperature sensing and heating elements associated with each sensor and generating a corresponding failed element output, wherein the plurality of sensor control means are each selected. Generating a faulty set output in response to the faulty element output of the corresponding measurement means for the working set, and generating a fault sensor output in response to receiving the faulty element output of the measurement means for both complementary sets; The system control means supplies a fault set and a fault sensor output of the plurality of sensor controls in relation to the identification of the corresponding sensor with respect to the system display means, and the system display means further responds to receiving the fault set and the fault sensor output. 12. The apparatus according to claim 11, further comprising means for separately displaying a failure set and a failure sensor in relation to identification of a corresponding sensor. 15. The apparatus according to claim 9, further comprising operator control means for selectively controlling the system control means to perform a selective online test of a plurality of sensors. 16. Each complement set comprises an independent heater element and two temperature sensing elements, each of a pair of associated probes relating to an independent heater element and an associated heater element, with two target temperature sensors and an associated heater element. A given one of the heater element and one temperature sensing element of one probe and the two temperature sensing elements of the other probe are associated as a first complementary set, independent of the other probe of the pair. The first heater element and the remaining temperature sensing element of the pair of probes are associated as a second complement.
The device according to item. 17. Each complementary set comprises a pair of integral heater / temperature sensing elements, each of said pair of probes of the sensor having a pair of integral heater / temperature sensing elements, each integral element being at a temperature. A heater having a resistance value that varies in a substantially linear relationship, capable of operating as a temperature sensing element to produce a sensed temperature output, and selectively activated when energized to heat an associated probe. Acting as an element, such an integrated heater / temperature sensing element of one of the pair of associated probes is each a given sensor of a given sensor associated with one of the integrated heater / temperature sensing elements of the other probe of the pair. First and second complementary sets of integrated heater / temperature sensing elements are configured for the associated probe of the pair, and the control means activates the first complementary set of integrated heater / temperature sensing elements in a normal monitor mode. And the second set is in a standby state and controls the biasing means to control a selected set of integral heaters / heaters associated with a given one of said given pair of probes of a given sensor. Apparatus according to claim 1, characterized in that a given one of the temperature sensing elements is energized. 18. A means for determining the failure of any temperature sensing heater element of a given sensor of the complementary set and generating a corresponding failed element output, wherein the control means determines for the selected set during normal monitor mode. Selecting the other set in a standby state in response to the failed element output of the means, and energizing means associated with the other one of the associated probes of the other set of integral heaters of the other set thus selected. Apparatus according to claim 17, characterized in that it controls to activate the temperature sensing element. 19. A biasing means comprising a bridge circuit having first and second branches connected in parallel between a first and a second connection point, and a complementary set of the first and second branches. First and second
And first and second low current sources connected in series with the third heater / temperature sensing element to form third and fourth connection points, respectively, wherein the first low current source is in the first branch. A first level of current sufficient to energize the first element as a subtracted element is provided, and a second low current source connected to the second branch is compared to the first level of current. Supplying a second level of current to the second element lower by a predetermined proportionality constant such that the second heater / temperature sensing element is only slightly heated by the second level of current flowing therethrough; An operational amplifier having first and second inputs and outputs, and a series connection of a bridge circuit connected to the first and second inputs of the operational amplifier, and respective voltage outputs at third and fourth connections; By the reciprocal of the proportionality factor Means for normalizing in response to the first and second levels of current flowing through the amplifier, wherein the operational amplifier generates a sensed temperature difference output indicative of a difference between the sensed temperature outputs of the complementary set of integrated heater / temperature sensing elements. Apparatus according to claim 17, characterized in that: 20. The biasing means comprises a first and a second of a given complement set.
Supply high and low level constant currents, respectively, differing by a known proportional coefficient to the integrated heater / temperature sensing elements of, to generate high and low level voltage outputs as sensed temperature outputs from these elements, respectively. The level of current heats the first integrated heater / temperature sensing element sufficiently that the first integrated heater / temperature sensing element acts as a heater and its corresponding probe can act as a heated probe. The apparatus according to claim 17, wherein the second integrated heater / temperature sensing element and its associated probe are only slightly heated by the low level current and thus can act as a reference probe. . 21. A determination means for determining a difference between the sensed temperature outputs and generating a corresponding sensed temperature difference output, the known level of the voltage output of the first and second integrated heater / temperature sensing elements being known. 21. The apparatus according to claim 20, further comprising means for changing the reciprocal of the proportional coefficient. 22. A judging means for generating a voltage value in a continuous reference range corresponding to a range of the sensed temperature output voltage value of the integrated heater / temperature sensing element in operation; Means for comparing a sensed temperature output voltage of the sensing element with a voltage value of a continuous reference range and generating a faulty element output when the sensed temperature output voltage is not within the continuous reference range. Apparatus according to claim (21).