JPH0321463Y2 - - Google Patents

Description

[Detailed description of the invention] This invention converts an analog signal based on a thermocouple inserted into molten steel and the voltage generated depending on the temperature difference between the temperature of this thermocouple and room temperature into a 12-bit digital signal, for example. This molten steel thermometer is equipped with an A/D converter that has only a predetermined processing capacity, and is capable of measuring molten steel temperature more accurately and at the same time automatically detecting thermocouple disconnection accidents. It is related to.

Molten steel thermometers that use the molten steel temperature measurement method shown in Japanese Patent Application Laid-Open No. 11821/1982 and perform measurement processing with a microcomputer generally use a consumable thermocouple (hereinafter simply referred to as thermocouple) for each molten steel temperature measurement. ) is inserted into molten steel, and the analog voltage signal generated by this thermocouple is amplified by an amplifier and input to an A/D converter, and the digital signal after A/D conversion is sent to a central processing unit (CPU). Incorporate into
This central processing unit sequentially calculates the amount of change in the temperature difference between the temperature of the thermocouple and the room temperature. When it is determined that the temperature of the thermocouple has reached thermal equilibrium with the molten steel, the temperature of the thermocouple at this point is determined as the molten steel temperature. A 12-bit A/D converter is normally used as an A/D converter in view of cost and the range of change in temperature difference between the temperature of the thermocouple and the room temperature.

However, in order to detect the molten steel temperature sufficiently accurately by the central processing unit, the amount of change calculation as described above is performed, for example.
Performed at 10msec intervals, and the amount of change is, for example, 20℃/
If the criterion for thermal equilibrium is that the temperature is below sec, then 1 bit of information must be at least 0.2°C (=
An A/D converter is required to indicate that the temperature is below 20°C/sec The temperature difference is 0℃~1800℃
, then 1 by this A/D converter
Bit information is approximately 0.44℃ (=1800℃−0℃/
4096), which exceeds 0.2℃, making it difficult to measure the molten steel temperature sufficiently accurately.

Furthermore, in conventional molten steel thermometers, a disconnection detection circuit had to be manually activated to detect a thermocouple disconnection accident, that is, a meltdown, which caused the problem of cumbersome operation.

Furthermore, even before starting measurement, it is necessary to check whether the thermocouple is disconnected. This check is normally carried out by a simple operation of checking whether or not the detected temperature shows a tendency to rise from room temperature when a flame such as a lighter is brought close to the thermocouple.

The present invention was developed in view of the above, and it is possible to measure the molten steel temperature with sufficient accuracy using a conventional molten steel thermometer that uses, for example, a 12-bit A/D converter, and at the same time automatically detects thermocouple disconnection. The purpose is to enable you to do so.

Therefore, the present invention includes a thermocouple inserted into molten steel, an amplifier that amplifies the voltage generated by the thermocouple, and a converter connected to the output side of the amplifier and having an A/D converter with a predetermined processing capacity. , a molten steel thermometer equipped with a central processing unit that determines the molten steel temperature based on temperature data from the converter, in which the output voltage of the amplifier is set at a temperature equal to or higher than a predetermined value at a stage before the A/D converter in the converter. A subtracter is connected to the connection line between the thermocouple and the amplifier to convert the voltage into a voltage corresponding to the temperature in the range, and if the connection line is in an unbroken state, the voltage generated by the thermocouple is affected. A voltage application circuit that applies a predetermined voltage whose polarity is opposite to that of the voltage generated by a normal thermocouple is connected through a high impedance disconnection detection resistor, and the output voltage of the amplifier and A comparator is provided for comparing the wire breakage detection signal with a predetermined wire breakage detection voltage and inputting the wire breakage detection signal to the central processing unit.

By adopting this configuration, the present invention converts the signal input to the A/D converter in the converter into a voltage corresponding to a temperature in a temperature range of a predetermined value or higher by converting the output voltage of the amplifier into a voltage using a subtracter. Since it is a converted signal, for example 1300℃~1800℃
It can be operated to perform A/D conversion only for the range of degrees Celsius. Therefore, even if the processing capacity of the A/D converter remains low, it is possible to perform temperature detection with the necessary accuracy in a specific temperature range.

However, if this is done, a new problem arises in that it becomes impossible to perform the simple disconnection detection operation that was carried out by holding a lighter close to the thermocouple at room temperature before starting the measurement.

In the present invention, a configuration that can deal with this new problem is adopted, and that is a voltage application circuit for automatic disconnection detection.

In this voltage application circuit, if the connection wire is not disconnected, a high impedance disconnection detection resistor is used to prevent any effect on the voltage generated by the thermocouple. can detect temperature without any problem. On the other hand, if the thermocouple is disconnected, the voltage on the thermocouple side is "0", so the voltage applied through the high-impedance disconnection detection resistor is the opposite sign of the normal voltage. A voltage will be output from the amplifier, and a comparator will compare this with the disconnection detection voltage, and a disconnection detection signal will be automatically output.

As a result, the molten steel thermometer of the present invention enables highly accurate temperature detection in the required range using an A/D converter with low processing capacity, and also eliminates the difficulty of detecting disconnection at room temperature. It is the perfect molten steel thermometer that solves problems and can automatically detect the state of melting during measurement.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of this embodiment. In the figure, 1 is a thermocouple inserted into the molten steel of a molten steel furnace (not shown), and 2 is a voltage (0 mV to 20 mV) generated at the thermocouple 1 inserted into the molten steel.
An amplifier that amplifies from 0V to 10V, 3 is a subtracter provided according to the present invention, and the amplified voltage 0V to 1800C corresponds to the temperature difference between the temperature of thermocouple 1 and room temperature from 0℃ to 1800℃.
Temperature difference between 10V and thermocouple 1 and room temperature is 1300℃~
Something that converts the voltage from 0V to 10V corresponding to 1800℃,
4 is a 12-bit A/D converter and subtracter 3
Converts the analog output voltage of 0V to 10V into a 12-bit digital signal. 5 is a voltage application circuit for detecting disconnection, and when thermocouple 1 is disconnected, the output voltage of amplifier 2 goes to a negative level (e.g. -80mV). For example, the disconnection detection resistor 5-1 is
1MΩ, the negative applied voltage is, for example, -2mV, and 6 is a comparator that compares the output voltage of amplifier 2 with a predetermined level of negative disconnection detection voltage V ₀ (for example, -20mV) and amplifies it. Voltage is disconnection detection voltage V ₀
Something that generates a disconnection detection signal when it is smaller than
7 is a central processing unit (CPU) which performs processing as shown in Japanese Patent Application Laid-Open No. 11821/1982 based on the 12-bit digital signal from the A/D converter 4 to obtain the molten steel temperature, and also calculates the molten steel temperature from the comparator 6. This indicates that the disconnection indicator lamp 8 is turned on when a disconnection detection signal is received.

Next, the operation of the molten steel thermometer configured as described above will be explained.

When thermocouple 1 is inserted into molten steel, this thermocouple 1
receives the thermal energy of the molten steel, and the temperature of the thermocouple 1 rapidly rises from room temperature. As the temperature of the thermocouple 1 rises, a voltage V ₁ proportional to the temperature difference between the thermocouple ₁ and _the room temperature is generated.
Voltage V ₃ corresponding to temperature difference 1300℃~1800℃
(0V to 10V), and this voltage _V3 is converted by the A/D converter 4 into a 12-bit digital signal. Here, A/D converter 4 has a temperature difference of 1300
Since the voltage 0V to 10V, which corresponds to 1800°C to 1800°C, is converted into a 12-bit digital signal, one bit is approximately 0.122°C (= 1800°C), which is well below the above 0.2°C.
℃−1300℃/4096). In the central processing unit 7, when the temperature difference is between 0°C and 1300°C, a signal indicating this temperature difference range is input from the A/D converter 4, and the molten steel temperature is not measured.
After that, when the temperature difference becomes 1300℃ or more, the temperature of the molten steel is measured based on the digital signal from the A/D converter 4, and if it is determined that the thermal equilibrium is reached as described at the beginning of the specification, the thermocouple 1 at this time is The temperature is displayed on a temperature display (not shown) as the molten steel temperature.

Further, the output voltage V ₂ of the amplifier 2 is input to the comparator 6 and compared with the disconnection detection voltage V ₀ . When a disconnection fault does not occur in the thermocouple 1, the comparator 6 does not output a disconnection detection signal, but if a disconnection fault occurs, the output voltage V ₂ of the amplifier 2 becomes the disconnection detection voltage.
Since the voltage is V ₀ or less, the comparator 6 outputs a disconnection detection signal. The central processing unit 7 is
When this disconnection detection signal is received, the disconnection indicator lamp 8 is turned on.

Figure 2 is a diagram of an analog recorder measuring thermocouple 1. As can be seen from the diagram, when thermocouple 1 is inserted into molten steel, the temperature difference between thermocouple 1 and room temperature rapidly increases. When it reaches a certain temperature, the temperature change becomes smaller. When this temperature change almost disappears, it is determined that thermal equilibrium has been reached, and the temperature of the thermocouple 1 at this time is determined to be the molten steel temperature.

As explained above, according to the present invention, it is possible to measure the molten steel temperature sufficiently accurately using a conventional A/D converter, and at the same time, wire breakage is easily detected because wire breakage is detected automatically. can be detected.

If the subtracter is configured so that the temperature can be detected with the necessary accuracy in a specific temperature range even if the processing capacity of the A/D converter is low, it is possible to It is also possible to effectively deal with a new problem in which the conventional simple disconnection detection operation, which was carried out by bringing a flame close to the thermocouple, becomes impossible.

That is, the molten steel thermometer of the present invention is, for example,
-We are not just applying a subtraction circuit like the one proposed in No. 170491 to thermocouples, but we are trying to solve new problems unique to thermocouples that arise only when a new configuration is adopted for such thermocouples. It has been perfected by having a structure that has remarkable functions and effects that allow it to do many things.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 is a diagram of an analog recorder when measuring molten steel temperature with a thermocouple. DESCRIPTION OF SYMBOLS 1...Thermocouple, 2...Amplifier, 3...Subtractor in a converter, 4...A/D converter in a converter, 5...Voltage application circuit, 6...Comparator, 7
...Central processing unit.

Claims (1)

[Claims for Utility Model Registration] A thermocouple inserted into molten steel, an amplifier that amplifies the voltage generated by the thermocouple, and an A/D converter connected to the output side of the amplifier and having a predetermined processing capacity. and a central processing unit that determines the temperature of molten steel based on temperature data from the converter, the output voltage of the amplifier is set to a predetermined value before the A/D converter in the converter. In addition to connecting a subtracter that converts the voltage into a voltage corresponding to a temperature in a temperature range greater than or equal to the value, a subtracter is connected to the connection line between the thermocouple and the amplifier, and if the connection line is in an unbroken state, a subtracter is connected to the voltage generated by the thermocouple. A voltage application circuit that applies a predetermined voltage whose polarity is opposite to that of the voltage generated by a normal thermocouple is connected through a high impedance disconnection detection resistor that does not affect the temperature of the amplifier. A molten steel thermometer, comprising: a comparator that compares an output voltage with a predetermined wire breakage detection voltage and inputs a wire breakage detection signal to the central processing unit.