JPH02195217A - Apparatus for correcting deterioration of temperature detector - Google Patents

Abstract

PURPOSE:To output a correcting signal or an alarm signal by taking out the outputs of main and secondary temperature detecting elements, and obtaining the deterioration of the main temperature detecting element based on the similar associated data which are changed with time as the associated reference data of the initial values of the elements when they are provided. CONSTITUTION:The outputs of a primary thermocouple 14 and secondary thermocouples 15 and 16 for correction are inputted into a microprocessor 45 through an analog multiplexer 41, an AD converter 43 and an I/O interface 44. The initial associated data are stored in a RAM 47. With the data as references, deterioration correcting operation is performed in the muP 45 based on the present associated data of the thermocouples 14 - 16 which are obtained in time. A primary thermocouple correcting signal (h) is obtained through a DA converter 48. When the deterioration exceeds the reference values, a primary thermocouple deterioration signal (g) is outputted through the interface 44. A program is stored in a ROM 46, and an initial command and the like are imparted with a operating switch 12. With this apparatus, the deterioration of the temperature detecting element which is arranged in a heat treating furnace 1 can be detected readily and accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to temperature measurement, and more specifically, to detecting deterioration of a thermocouple for temperature measurement and performing correction calculations to perform accurate temperature measurement. The present invention relates to a temperature detector deterioration correction device for obtaining a deterioration alarm.

BACKGROUND OF THE INVENTION Conventionally, in this type of temperature measurement, the thermocouple is periodically removed and the accuracy is checked using a thermocouple verification device.

Problems to be Solved by the Invention In conventional temperature measurement, deterioration of thermocouples must be tested using an off-line thermocouple temperature verification device. Alternatively, deterioration of thermocouples has been indirectly discovered from the quality of products that have been heat-treated based on temperature measurement.

In general, the deterioration of thermocouples increases as the operating temperature increases and the longer the operating time.

The present invention has been made in view of the above-mentioned conventional situation,
Therefore, an object of the present invention is to provide a new method that enables more accurate temperature measurement by detecting thermocouple deterioration online when using a thermocouple, and outputting a thermocouple electromotive force correction signal or deterioration alarm. The object of the present invention is to provide a correcting device.

Means for Solving the Problems In order to achieve the above object, the temperature sensor deterioration correction device according to the present invention captures the output signals of the main temperature detection element and the sub temperature detection element, It is configured to determine the deterioration of the main temperature detection element from similar related data that changes over time as a value related data reference, and output a correction signal or alarm signal for the main temperature detection element.

Principle of the Invention When a thermocouple is installed as shown in Figure 2, there is a thermal gradient inside and outside the furnace with the furnace wall as the center.This thermal gradient is due to the flow of heat and is determined by the installation of the thermocouple. .

The main thermocouple 14, side thermocouple 15, and side thermocouple 16 are used to measure this thermal gradient.The side thermocouple 15 is preferably set at an intermediate temperature between the outside temperature and the furnace temperature.The side thermocouple 15 is the main thermocouple. If the temperature is close to 14, the side thermocouple 15 will deteriorate at the same time as the main thermocouple 14, and deterioration of the main thermocouple 14 cannot be detected.On the other hand, if the side thermocouple 15 is close to the side thermocouple 16, the main The thermal deterioration of the side thermocouple 15, which cannot detect the deterioration of the thermocouple 14, is negligible compared to that of the main thermocouple 14 because the side thermocouple 15 measures a temperature lower than that of the main thermocouple 14.

In a six-month aging test of the R thermocouple, the temperature at 1600℃ was -6
There are reports that the deterioration is -20°C at 0°C and 1400°C, and deterioration decreases rapidly at lower temperatures.

In order to adjust the temperature of the side thermocouple 15 to an intermediate temperature, the length of the thermocouple protection tube 12 inserted into the furnace may be changed by adjusting the thermocouple support portion 13.

Embodiment Next, a preferred embodiment of the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a schematic block diagram showing an embodiment of a temperature detector deterioration correction device according to the present invention.

Referring to FIG. 1, reference number 1 indicates a heat treatment furnace (for example, an electric furnace) used for heat treatment of objects, and a part of the furnace wall 11 of the heat treatment furnace is exposed to the outside of the furnace (outside air). Protection tube 1
2 is fixed by a support part 13. A heater 2 for heating the furnace is also arranged within the heat treatment furnace 1 . Protection tube 12
A detection output of a temperature detection element such as a thermocouple is connected to a signal processing circuit to be described later by a signal line 3 from the terminal portion 12a.

FIG. 2 (al(b)) is a specific configuration diagram of the vicinity of the protection tube 12 and a measured temperature curve diagram. The embodiment shown in FIG. 2 is an example in which a thermocouple is used as the temperature detection element.

Referring to FIG. 2 1al, reference numeral 11 indicates a furnace wall of a heat treatment furnace used for heat treatment of materials, and a protective tube 12 having a terminal portion 12a for taking out measurement data is mounted on the furnace wall 11 as a supporting portion. It is supported and fixed by 13. Protection tube 1
2, a part including the terminal portion 12a is exposed to the outside of the furnace wall 11 (outside air).

Inside the protection tube 12, a main thermocouple for measurement 14, a side thermocouple 16 for measuring outside air using the thermocouple, and a side thermocouple 15 disposed between them are arranged as shown.

The causes of thermocouple deterioration are widely considered, but are mainly due to the operating temperature and operating time. Figure 2(a) l
As can be seen from b), the main thermocouple 14 is exposed to higher temperatures than the other thermocouples (the side thermocouple 15 and the side thermocouple 161), so its deterioration is faster.

FIG. 3 is a block diagram showing one embodiment of a signal processing circuit used in the present invention.

Referring to FIG. 3, the main thermocouple 14 for measuring temperature
The outputs of a plurality of side thermocouples (two thermocouples 15 and 16 in the illustrated embodiment) for correcting the deterioration of the main thermocouple 14 are output from an analog multiplexer 41, an A/D converter 43,
It is input to the microprocessor (uP) 45 via the I10 interface circuit 44 to set initial related data at the time of thermocouple installation, and these are stored on the memory RAM 47. A main thermocouple 14 and two sets of side thermocouples 15 obtained over time based on the stored initial related data.
16 current related data, thermocouple deterioration correction calculation is performed by the calculation of μP 45, and the result is outputted as the main thermocouple correction signal via the D/A converter 48.

In addition, if the deterioration of the main thermocouple exceeds a certain standard value, the I
10 interface circuit 44 as the main thermocouple correction signal g.

Note that a program is stored in the ROM a6.

In FIG. 3, the cold junction correction circuits for the main thermocouple 14 and side thermocouples 15, 16 are omitted.

The operation switch 42 is an input switch for giving an initial command signal etc. when setting the thermocouple.

The signal processing circuit shown in FIG. 3 takes in three sets of inputs: the main thermocouple T4 and the side thermocouples 15 and 16. Temperature measurement is performed with the main thermocouple 14 and the side thermocouple 15° 16 is used for correcting deterioration of the main thermocouple 14.

That is, the main thermocouple 14 and the sub-thermocouple when a new thermocouple is installed.

The relationship between pair 15 and 16 is stored on the RAM 47. When the main thermocouple 14 deteriorates due to long-term use of the thermocouple at high temperatures, the temperature balance between the main thermocouple 14 and the side thermocouples 15 and 16 changes from when it was new (or when the thermocouple was initially installed). An example of these software processes is shown in FIG.

Here, as an example of the processing of the initial related data of the main thermocouple 14 and the two side thermocouples 15 and 16 and the current related data that have been used for a long time at high temperatures, the following is obtained when the proportional relationship is corrected.

However, the initial values of the main thermocouple 14, side thermocouple 15, and side thermocouple 16 are T1, T2, and T3, and the values after deterioration are Tr'
, T2' and Ts'. Here, if the deterioration of the main thermocouple 14 is α and the deterioration of the side thermocouples 15 and 16 can be ignored, then ITI-Tz at the initial value:
1T2-T3) to the values after deterioration T1°, T2°2T
3T deterioration αte is shown as l(T+'+al-T2'l:
(T2°-Ts'), that is, the relationship of equation (1) is obtained.

(Tl-T21: (Tz-Till(T1'+al-
T2'l: (T2°-73'1...
+1) From this formula.

The correction data displayed in Fig. 4 indicates the deterioration amount α, α
In addition to the above-mentioned method of obtaining the proportional part, it is also possible to obtain it with a weight based on the deterioration data experimentally, for example, by multiplying it by a certain constant to further improve the accuracy of the deterioration data.

Further, in this embodiment, the number of side thermocouples is two, but the effect of increasing the accuracy by changing the number of side thermocouples can also be determined by calculation.

Furthermore, although the thermocouple according to the present invention has been described as having a main thermocouple and a side thermocouple enclosed in the same protection tube as shown in Fig. 2, it is possible to obtain the same thermal relationship by using separate thermocouples. It is also possible to obtain a similar effect with a temperature sensor installed in the shape.

According to the present invention, it is possible to easily obtain a deterioration correction device having a function of taking in the signals of the main thermocouple and side thermocouples and determining the deterioration of the main thermocouple from current data obtained over time based on the initial data.

In the present invention, examples of thermocouple deterioration correction and thermocouple deterioration alarm are shown as methods of using deterioration data, but only one of them may be used.

In the embodiments described above, a thermocouple is used as the temperature detection element, but a resistance temperature detector, a thermistor, or the like can be used instead of the thermocouple.

As described in detail, according to the present invention, it is possible to easily and accurately detect deterioration of a temperature detection element disposed in a heat treatment furnace.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the entire embodiment of the temperature detector deterioration correction device according to the present invention, and FIGS. 2(a) (b)
) is an enlarged partial configuration diagram of the vicinity of the protection tube fixed to the heat treatment furnace, FIG. 3 is a block configuration diagram showing one embodiment of the signal processing device, and FIG. 4 is an operation flowchart of the present invention. 1... Heat treatment furnace, 2... Heater, 3... Signal line,
4... Signal processing device, 6... Power line, 11... Furnace wall, 12... Protection tube, 13... Support part, 14...
Main thermocouple, 15. 16... Side thermocouple, 41... Analog multiplexer, 42... Operation switch, 43.
...A/D converter, 44...! 10 interface circuit, 45...μP, 46...RAM, 47.
...RAM, 48...D/Hachiverta Patent applicant: Okura Electric Co., Ltd. Agent: Patent attorney: Yutabe Kumagai

Claims (1)

[Claims] The output signals of the main temperature detection element and the sub temperature detection element are taken in, and the deterioration of the main temperature detection element is determined from similar related data that changes over time using the related data of the initial values of these temperature detection elements as a reference, and the main temperature is determined. A temperature sensor deterioration correction device characterized by outputting a detection element correction signal or an alarm signal.