JP2008107089A - Thermocouple temperature sensor temperature drift diagnostic device - Google Patents

Abstract

The present invention accurately diagnoses the occurrence of temperature drift in a thermocouple temperature sensor.
In a first temperature range (temperature range where temperature drift is likely to occur) S1, a thermocouple temperature sensor is used in each temperature range (temperature range 50 ° C.) in a positive direction corresponding to the temperature range. Apply a weight to The usage time of the thermocouple temperature sensor in each temperature range in the second temperature range (temperature range where temperature drift will be eliminated) S2 is weighted in the negative direction according to the temperature range. The usage time of the thermocouple temperature sensor weighted in each temperature range in the first temperature region S1 and the second temperature region S2 is added, and the added value is used as the drift amount. Based on this drift amount, the occurrence of temperature drift is diagnosed.
[Selection] Figure 1

Description

  The present invention relates to a temperature drift diagnosing device for a thermocouple temperature sensor for diagnosing the state of occurrence of a temperature drift that occurs when a thermocouple temperature sensor is exposed to a high temperature.

  Conventionally, thermocouple temperature sensors have been used in controllers, recorders, thermometers and the like used in temperature control and the like. As thermocouple temperature sensors, K thermocouples (alloy thermocouples with nickel and chromium as components) and R thermocouples (alloy thermocouples with platinum and rhodium as components) have a specific temperature range called short range ordering. It is known that there is a temperature drift at. For example, when the thermocouple temperature sensor is exposed to a high temperature of 350 to 600 ° C., the thermoelectromotive force changes, a temperature drift occurs in the measured temperature, and the detection accuracy decreases.

  In response to such a decrease in detection accuracy, Patent Document 1 discloses a time measurement unit that measures elapsed time at each temperature of the thermocouple temperature sensor, a reference operating temperature and a lifetime (time) of the thermocouple temperature sensor. A life information storage unit that stores the relationship, and a temperature history storage unit that stores the actual use temperature with time at the temperature that promotes deterioration exceeding the reference use temperature, and stores the actual use temperature with time, are stored in the temperature history storage unit. Further, it is described that the lifetime of the thermocouple sensor is predicted based on the actual use temperature, the elapsed time measured by the time measurement unit, and the reference use temperature and the life (time) stored in the life information storage unit.

  According to this description, in Patent Document 1, the deterioration coefficient is taken into account at a temperature exceeding the reference operating temperature, and the operating time at each temperature of the thermocouple temperature sensor is integrated, and the integrated value of the operating time is calculated. It is considered that the remaining lifetime of the thermocouple temperature sensor is predicted by subtracting from the lifetime (time) associated with the reference operating temperature.

Japanese Patent Laid-Open No. 4-76799

  However, in the technique disclosed in Patent Document 1 described above, the use temperature and the use time may act in a direction to eliminate the temperature drift in a temperature range above a specific temperature range where short range ordering occurs. First, all the usage time at each temperature of the thermocouple temperature sensor is integrated as a positive value. For this reason, the integrated value of the usage time includes a time in which the temperature drift is eliminated, and accurate life prediction is hindered. In Patent Document 1, the lifetime of the thermocouple temperature sensor is predicted. However, for example, when the integrated value of the usage time exceeds a predetermined threshold, an abnormality may be notified, and the lifetime is predicted. As in this case, accurate diagnosis of the occurrence of temperature drift is prevented.

  The present invention has been made to solve such a problem, and the object of the present invention is to provide a temperature drift of a thermocouple temperature sensor capable of accurately diagnosing the occurrence of temperature drift of the thermocouple temperature sensor. It is to provide a diagnostic device.

  In order to achieve such an object, the present invention relates to a temperature drift diagnostic apparatus for a thermocouple temperature sensor that diagnoses the occurrence of temperature drift that occurs when the thermocouple temperature sensor is exposed to a high temperature. The thermocouple temperature sensor usage time at the temperature at which the temperature will be applied is weighted according to the temperature, and the thermocouple temperature sensor usage time at the temperature at which the temperature drift will be eliminated is weighted according to the temperature. A weighting means to be applied, a drift amount calculating means for obtaining an added value of the use time of the thermocouple temperature sensor to which the weight is applied as a drift amount, and a temperature of the thermocouple temperature sensor based on the drift amount obtained by the drift amount calculating means Temperature drift diagnosis means for diagnosing the state of occurrence of drift is provided.

  For example, in the present invention, the usage time of the thermocouple temperature sensor in each temperature range in the first temperature range defined as the temperature range in which temperature drift will occur is weighted in the positive direction according to the temperature range. And weighting in the negative direction according to the temperature range for the usage time of the thermocouple temperature sensor in each temperature range in the second temperature range determined as the temperature range where temperature drift will be eliminated Means, drift amount calculating means for obtaining, as a drift amount, an added value of the use time of the thermocouple temperature sensor weighted in each temperature range in the first temperature range and the second temperature range, and drift amount calculating means Temperature drift diagnosing means for diagnosing the state of occurrence of temperature drift of the thermocouple temperature sensor based on the drift amount obtained by the above.

  Thereby, in the usage time of the thermocouple temperature sensor in each temperature range (for example, temperature range 50 degreeC) in the 1st temperature range (temperature range (for example, 350-600 degreeC) where a temperature drift will occur). Weighting in the positive direction according to the temperature range is performed, and each temperature range (for example, temperature width 50) in the second temperature range (temperature range (for example, 600 to 1000 ° C.) where temperature drift will be eliminated). ° C), the thermocouple temperature sensor is weighted in the negative direction according to the temperature range, and the thermocouple is weighted in each temperature range in the first temperature range and the second temperature range. The added value of the usage time of the temperature sensor is obtained as the drift amount. In this case, the drift amount indicates a difference between the generation amount of the temperature drift occurring in the first temperature region and the elimination amount of the temperature drift occurring in the second temperature region, and the temperature of the thermocouple temperature sensor is based on this drift amount. The occurrence of drift is diagnosed.

  In the present invention, the weighting in the first temperature range is, for example, in accordance with the amount of temperature drift generated per unit time in each temperature range, and the weighting in the positive direction is increased in the temperature range where the amount of temperature lift generation is large. In the temperature range where the amount of temperature drift is small, the weighting in the positive direction is made small. Further, the weighting in the second temperature range is, for example, in accordance with the temperature drift elimination amount per unit time in each temperature range, and in the temperature range where the temperature drift elimination amount is large, the weighting in the negative direction is increased. In the temperature range where the amount of drift cancellation is small, the negative weighting is reduced. In this way, by weighting the operating temperature of the thermocouple temperature sensor in each temperature range, the amount of temperature drift that occurs in the first temperature region and the amount of temperature drift that occurs in the second temperature region are accurately determined. It becomes possible to ask for.

  In the present invention, the method of obtaining the drift amount is not limited to the method of dividing into the above-described temperature range. For example, a polynomial or the like indicating the tendency of the amount of occurrence of temperature drift may be created as a curve, and this curve may be used as a curve indicating weighting for integration. In this case, it is not necessary to divide into the temperature range, and the process becomes simple.

  In the present invention, the temperature drift diagnostic means has a function of notifying the abnormality of the thermocouple temperature sensor when the drift amount is a positive value and the drift amount is equal to or greater than a predetermined threshold value. Further, when the drift amount is a positive value, it has a function of correcting the measured temperature of the thermocouple temperature sensor according to the drift amount. In addition, when the drift amount is a positive value and the drift amount is equal to or greater than a predetermined threshold value, the thermocouple temperature sensor is heated for a predetermined time at a predetermined temperature in the second temperature region as necessary. Have When the thermocouple temperature sensor is heated at a predetermined temperature in the second temperature region for a predetermined time, the temperature and time are applied in a direction to eliminate the temperature drift, and the detection accuracy can be recovered.

  According to the present invention, the use time of a thermocouple temperature sensor at a temperature at which a temperature drift will occur is weighted according to the temperature, and the thermocouple temperature sensor at a temperature at which the temperature drift will be eliminated. Since the usage time is weighted in the negative direction according to the temperature, and the added value of the usage time of the weighted thermocouple temperature sensor is obtained as the drift amount, the amount of temperature drift and the temperature drift The amount of elimination can be accurately obtained, and the occurrence of temperature drift of the thermocouple temperature sensor can be accurately diagnosed from the amount of drift indicating the difference between the amount of occurrence of the temperature drift and the amount of elimination.

Further, according to the present invention, when the drift amount is a positive value and the drift amount is equal to or greater than a predetermined threshold, the abnormality of the thermocouple temperature sensor is notified, so that it is too early or too late. Therefore, it is possible to prompt the exchange of the thermocouple temperature sensor at an appropriate timing.
Further, according to the present invention, when the drift amount is a positive value, by correcting the measured temperature of the thermocouple temperature sensor according to the drift amount, the accuracy is always improved regardless of whether or not the temperature drift occurs. High temperature measurement can be performed.
According to the present invention, when the drift amount is a positive value and the drift amount is equal to or greater than a predetermined threshold value, the thermocouple temperature sensor is heated at a predetermined temperature in the second temperature region for a predetermined time. By doing so, the temperature and time are made to act in the direction in which the temperature drift is eliminated, and the detection accuracy can be recovered.

  Hereinafter, the present invention will be described in detail with reference to the drawings. First, before describing the embodiment of the present invention, an outline of the present invention will be described.

〔Overview〕
1 shows the thermocouple temperature sensor operating temperature range (° C) on the horizontal axis, and the thermocouple temperature sensor operating time (integrated time (h)) and the amount of temperature drift per unit time (° C) on the vertical axis. It is a figure which shows as a graph represented as.

  In the same figure, graph G1 (bar graph) shows the usage time of the thermocouple temperature sensor in each temperature range divided into temperature ranges of 50 ° C., and graph G2 (line graph) shows each of the temperature ranges divided into 50 ° C. Indicates the amount of temperature drift per unit time of the thermocouple temperature sensor in the temperature range.

  Note that the graphs G1 and G2 in FIG. 1 are shown for reference in order to explain the outline of the present invention, and such data are not actually obtained. The generation amount of the temperature drift per unit time of the thermocouple temperature sensor is generally considered to show such a tendency as shown by the graph G2.

  In the graph G2, a negative value of the amount of temperature drift generated per unit time indicates the ability to eliminate the temperature drift, and does not actually generate a negative temperature drift. That is, in the graph G2, the positive value of the temperature drift generation amount per unit time indicates the temperature drift generation amount per unit time, while the negative value of the temperature drift generation amount per unit time is the per unit time. This shows the amount of temperature drift eliminated.

  In the graph G2, the generation amount of the temperature drift per unit time of the thermocouple temperature sensor takes a positive value in the temperature range of 350 to 600 ° C., and takes a negative value in the temperature range of 600 to 1000 ° C. Therefore, in the present invention, the temperature region of 350 to 600 ° C. is set as the temperature region (first temperature region) S1 where the temperature drift will occur, and the temperature region of 600 to 1000 ° C. will be eliminated. It is defined as a temperature region (second temperature region) S2.

  Then, the use time of the thermocouple temperature sensor in each temperature range in the first temperature range S1 is weighted in the positive direction according to the temperature range, and the thermocouple in each temperature range in the second temperature range S2 The usage time of the temperature sensor is weighted in the negative direction according to the temperature range.

  In this case, in the first temperature region S1, weighting in the positive direction is increased in the temperature range where the amount of temperature drift is large in accordance with the amount of temperature drift generated per unit time in each temperature range, and temperature drift occurs. In the temperature range where the amount is small, the weighting in the positive direction is reduced. In the second temperature region S2, the weighting in the negative direction is increased in the temperature range where the temperature drift elimination amount is large according to the temperature drift elimination amount per unit time of each temperature range, and the temperature drift elimination amount is small. Reduce the negative weighting in the temperature range.

  Then, the usage time of the thermocouple temperature sensor weighted in each temperature range in the first temperature region S1 and the second temperature region S2 is added, and the added value of the usage time is set as the drift amount.

  FIG. 2 shows the usage time in which weighting is performed in each temperature range in the first temperature region S1 and the second temperature region S2. As described above, the use time in which the temperature ranges in the first temperature region S1 are weighted has a positive value, and the use time in which the temperature ranges in the second temperature region S2 have been weighted has a negative value. . The amount of drift is obtained by adding these usage times.

  Based on this drift amount, the temperature drift occurrence state of the thermocouple temperature sensor is diagnosed. For example, if the drift amount is a positive value, it is determined that there is a high possibility that a temperature drift has occurred and an error has occurred in the measured temperature. If the drift amount is a negative value, it is determined that there is no temperature drift and there is a low possibility that an error has occurred in the measured temperature.

  Further, when the drift amount is a positive value and the drift amount is equal to or greater than a predetermined threshold, an abnormality of the thermocouple temperature sensor is notified. Thereby, it is possible to prompt replacement of the thermocouple temperature sensor at an appropriate timing without being too early or too late.

  When the drift amount is a positive value, the measured temperature of the thermocouple temperature sensor is corrected according to the drift amount. This makes it possible to always perform highly accurate temperature measurement regardless of the occurrence of temperature drift.

  Further, when the drift amount is a positive value and the drift amount is equal to or greater than a predetermined threshold value, for example, when the user desires a free time when the furnace is not used, the thermocouple temperature sensor is set to the second value. Heating (aging) is performed for a predetermined time at a predetermined temperature in the temperature region S2. This aging allows the temperature and time to act in the direction in which the temperature drift is eliminated, thereby recovering the detection accuracy.

  When the thermocouple temperature sensor is aged for a predetermined time or longer in the second temperature region S2, the temperature and time act to return to the original detection accuracy. In this case, even if the aging time is long, a negative temperature drift hardly occurs.

  In the above description, the drift amount is obtained by dividing the temperature range, but for example, a polynomial or the like indicating the tendency of the temperature drift generation amount is formed as a curve, and this curve is integrated as a weighting curve. May be used to obtain the drift amount. In this case, it is not necessary to divide into the temperature range, and the process becomes simple.

  In addition, as described above, in the present invention, round calculation is performed such that weighting is performed without directly integrating the drift temperature, and then the drift temperature is converted into the drift temperature. This is because the amount of drift can be easily adjusted according to the situation at the site. That is, the actual drift temperature varies greatly depending on the installation conditions at the site, such as the diameter of the sensor and the depth of insertion into the device. On the other hand, if the tendency of drift is assumed to be similar and only weighting is performed using a coefficient, the drift amount can be easily adjusted according to the situation at the site. If it is easily realized, a drift per hour time may be directly used for the calculation instead of the weighted data.

[Embodiment 1]
FIG. 3 is a block diagram of a temperature measurement system using an embodiment of a temperature drift diagnostic apparatus for a thermocouple temperature sensor according to the present invention. In the figure, 1 is a thermocouple temperature sensor, 2 is a temperature drift diagnostic apparatus according to the present invention, 3 is a buzzer, and 4 is a display. In FIG. 3, the thermocouple temperature sensor 1 is a K thermocouple.

  The temperature drift diagnosis apparatus 2 is realized by hardware including a processor and a storage device and a program that realizes various functions in cooperation with these hardware. The temperature drift diagnosis function is a function unique to the present embodiment. Have.

  Hereinafter, the temperature drift diagnostic function of the temperature drift diagnostic apparatus 2 will be described with reference to the flowchart shown in FIG. The temperature drift diagnostic apparatus 2 repeats the processing of this flowchart every measurement period T.

  In step 101, the temperature drift diagnostic apparatus 2 checks whether the thermocouple temperature sensor 1 is a K thermocouple. In this case, since the thermocouple temperature sensor 1 is a K thermocouple, the process proceeds to step 102 in response to YES in step 101. If the thermocouple temperature sensor 1 is not a K thermocouple, the process ends.

  In step 102, it is confirmed whether or not the thermocouple temperature sensor 1 has been replaced. If the thermocouple temperature sensor 1 is replaced with a new thermocouple temperature sensor (YES in step 102), the process proceeds to step 103. If the thermocouple temperature sensor 1 is not replaced, the process immediately proceeds to step 105. Here, it is assumed that the thermocouple temperature sensor 1 is replaced with a new thermocouple temperature sensor.

  In this case, the temperature drift diagnosis apparatus 2 sets the sensor type of the thermocouple temperature sensor 1 (step 103), and initializes the timer TM (n) for the K thermocouple special temperature zone (step 104). By this initialization, the timer value of the timer TM (n) becomes zero.

  Here, the K thermocouple special temperature zone is a temperature zone in which the first temperature region S1 and the second temperature region S2 described above are combined. In the present embodiment, the temperature range is 350 to 1000 ° C. Further, in the present embodiment, the number of divisions obtained by dividing the K thermocouple special temperature zone by the temperature range of 50 ° C., that is, the number “13” of each temperature range of the K thermocouple special temperature zone is N, and n is 1 to N The value up to is assumed. Therefore, the timer TM (n) includes 13 timers TM (1) to TM (13).

  Next, the temperature drift diagnostic apparatus 2 checks the measured temperature (current temperature) of the thermocouple temperature sensor 1 (step 105), and if the current temperature is in the K thermocouple special temperature zone (350 to 1000 ° C.) (step 105). 106, YES), it is examined in which temperature range of the K thermocouple special temperature zone the current temperature is located (step 107). That is, each temperature range of the K thermocouple special temperature zone is set to TW (n), and the temperature range TW (n) where the current temperature is located is examined.

  Then, the measurement period T is added to the timer value (previous value) of the timer TM (n) corresponding to the temperature range TW (n) where the current temperature is located, and the timer value (current value) of the timer TM (n) (Step 108). For example, if the current temperature is located in the temperature range TW (1), the measurement period T is added to the timer value (previous value) of the timer TM (1) corresponding to the temperature range TW (1), and the timer TM The timer value (current value) in (1) is used. Thereby, the usage time of the thermocouple temperature sensor 1 in the temperature range TW (1) is integrated into the timer TM (1).

  Then, the temperature drift diagnostic device 2 sets the amount of temperature drift generated per unit time in the temperature range TW (n) as δ (n), and sets the amount of temperature drift δ (n) as the timer value of the timer TM (n). Is used to obtain the usage time weighted in the temperature range TW (n), the usage time weighted in each temperature range TW (n) is added, and this added value is used as the drift amount ΔD. (Step 109).

  Here, the temperature drift generation amount δ (n) per unit time in the temperature range TW (n) is a positive value in the first temperature region S1, and a negative value in the second temperature region S2. Negative values indicate the amount of temperature drift eliminated. Further, the temperature drift generation amount δ (n) per unit time in the temperature range TW (n) is measured according to the individual instrumentation, and an appropriate value is stored in the temperature drift diagnostic device 2. .

  Next, the temperature drift diagnostic apparatus 2 checks whether or not the drift amount ΔD is a positive value (step 110). If the drift amount ΔD is a positive value (YES in step 110), it is determined that a temperature drift has occurred and there is a high possibility that an error has occurred in the measured temperature, and the routine proceeds to step 111. If the drift amount ΔD is a negative value (NO in step 110), it is determined that there is no temperature drift and there is a low possibility that an error has occurred in the measured temperature, and the process proceeds without proceeding to step 111. finish.

  In step 111, the drift amount ΔD is compared with a predetermined threshold value ΔDth. The threshold value ΔDth is a limit temperature determined by the user, and differs depending on the purpose, and is thus designated by the user. When the drift amount ΔD is larger than the threshold value ΔDth (YES in step 111), the temperature drift diagnostic device 2 issues an alarm (step 112) and notifies the abnormality of the thermocouple temperature sensor 1. When the drift amount ΔD is equal to or less than the threshold value ΔDth, the temperature drift diagnostic apparatus 2 ends the process without issuing an alarm. In the same manner, the processing operation described above is repeated every measurement cycle T.

[Embodiment 2]
In the first embodiment, when the drift amount ΔD is larger than the threshold value ΔDth (YES in step 111), the abnormality of the thermocouple temperature sensor 1 is notified. On the other hand, in the second embodiment, as shown in the flowchart corresponding to FIG. 4 in FIG. 5, when the drift amount ΔD is a positive value (YES in step 110), the measured temperature is determined according to the drift amount ΔD. Is corrected (step 113).

[Embodiment 3]
In the third embodiment, as shown in the flowchart corresponding to FIG. 4 in FIG. 6, when the drift amount ΔD is larger than the threshold value ΔDth (YES in step 111), the furnace temperature is automatically set as necessary. For example, the aging of the thermocouple temperature sensor 1 is started (step 115). During aging, even if the drift amount ΔD is a positive value, the routine does not proceed to step 111 (YES in step 114).

  In the above-described embodiment, each temperature range in the first temperature region S1 and the second temperature region S2 is set to a temperature range of 50 ° C., but it goes without saying that the temperature range is not limited to 50 ° C. Moreover, it does not necessarily need to be an equal temperature range, and the temperature range of each temperature range may differ.

  In the above-described embodiment, the first temperature region S1 and the second temperature region S2 are connected to each other, but a case where they are separated from each other is also conceivable. Moreover, you may make it perform prediction of the lifetime of a thermocouple temperature sensor as one form of the diagnosis of the generation | occurrence | production state of the temperature drift of a thermocouple temperature sensor.

It is a figure which shows the graphs G1 and G2 expressed by making the operating temperature range of a thermocouple temperature sensor into a horizontal axis | shaft, and having the usage time of the thermocouple temperature sensor and the generation amount of the temperature drift per unit time as a vertical axis | shaft. It is a figure which shows the use time of the thermocouple temperature sensor to which each temperature range was weighted in the 1st temperature range and the 2nd temperature range. It is a block diagram of the temperature measurement system using one Embodiment of the temperature drift diagnostic apparatus of the thermocouple temperature sensor which concerns on this invention. It is a flowchart (Embodiment 1) for demonstrating the temperature drift diagnostic function which the temperature drift diagnostic apparatus used with this temperature measurement system has. It is a flowchart (Embodiment 2) for demonstrating the temperature drift diagnostic function which the temperature drift diagnostic apparatus used with this temperature measurement system has. It is a flowchart (Embodiment 3) for demonstrating the temperature drift diagnostic function which the temperature drift diagnostic apparatus used with this temperature measurement system has.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Thermocouple temperature sensor, 2 ... Temperature drift diagnostic apparatus, 3 ... Buzzer, 4 ... Display, S1 ... 1st temperature range, S2 ... 2nd temperature range.

Claims (5)

In a thermocouple temperature sensor temperature drift diagnostic device for diagnosing the occurrence of temperature drift that occurs when a thermocouple temperature sensor is exposed to high temperatures,
The use time of the thermocouple temperature sensor at a temperature at which the temperature drift will occur is weighted according to the temperature, and the use time of the thermocouple temperature sensor at a temperature at which the temperature drift will be eliminated Weighting means for weighting according to the temperature,
Drift amount calculation means for obtaining an added value of the usage time of the thermocouple temperature sensor subjected to the weighting as a drift amount;
A temperature drift diagnosing device for a thermocouple temperature sensor, comprising: a temperature drift diagnosing unit for diagnosing a temperature drift occurrence state of the thermocouple temperature sensor based on a drift amount obtained by the drift amount calculating unit. In a thermocouple temperature sensor temperature drift diagnostic device for diagnosing the occurrence of temperature drift that occurs when a thermocouple temperature sensor is exposed to high temperatures,
The use time of the thermocouple temperature sensor in each temperature range in the first temperature range defined as the temperature range in which the temperature drift will occur is weighted in the positive direction according to the temperature range, Weighting means for weighting the use time of the thermocouple temperature sensor in each temperature range in the second temperature range determined as a temperature range in which temperature drift will be eliminated in a negative direction according to the temperature range; ,
A drift amount calculating means for obtaining an added value of a use time of the thermocouple temperature sensor subjected to the weighting in each temperature range in the first temperature region and the second temperature region as a drift amount;
A temperature drift diagnosing device for a thermocouple temperature sensor, comprising: a temperature drift diagnosing unit for diagnosing a temperature drift occurrence state of the thermocouple temperature sensor based on a drift amount obtained by the drift amount calculating unit. In the temperature drift diagnostic apparatus of the thermocouple temperature sensor according to claim 1,
The temperature drift diagnostic means includes
The thermocouple temperature sensor temperature drift diagnostic device, wherein when the drift amount is a positive value and the drift amount is equal to or greater than a predetermined threshold, an abnormality of the thermocouple temperature sensor is notified. In the temperature drift diagnostic apparatus of the thermocouple temperature sensor according to claim 1,
When the drift amount is a positive value, the temperature drift diagnosis unit corrects the measured temperature of the thermocouple temperature sensor according to the drift amount. In the temperature drift diagnostic apparatus of the thermocouple temperature sensor according to claim 1,
The drift amount diagnostic means includes
If the drift amount is a positive value and the drift amount is equal to or greater than a predetermined threshold value, the thermocouple temperature sensor is heated for a predetermined time at a predetermined temperature in the second temperature region as necessary. A temperature drift diagnostic apparatus for a thermocouple temperature sensor.

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