SU1500797A1 - Automatic methane monitor for coal mines - Google Patents

Description

The invention relates to safety in the mining industry. The goal is to increase the speed and reliability of methane control. The device contains a sensor 1 of methane concentration, a corrective element 2, an inertial element 3 with variable inertia2

power, inverter 4 signal polarity, analog adder 5, executive unit 6 and amplifier (V) 7 with deadband. The signal from the methane concentration sensor 1 is fed to the input of the correction link 2. From here, the signal goes to the analog adder 5 in two ways through the inverter 4 signal polarities and through the link 3. From the output of the adder 5, the signal goes to the input 7. 7. Depending on the magnitude of this signal At 7 it forms the control action for link 3. The value of the time constant of link 3 is chosen from the conditions of optimal speed, with Executive unit 6 connected to the output of link 3. In dynamic mode, the value of the time constant of link 3 changes in isimosti dynamics of changes in methane concentration at the sensor 1. This improves noise immunity of the device during short bursts of the methane concentration and electrical surges. 1 il.

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The invention relates to safety in the mining industry and can be used to control the explosiveness of the mine atmosphere at the sphere and to generate commands for protective power outage when the maximum permissible standards of methane content in the mine workings are exceeded. ten

The aim of the invention is to increase the speed and reliability of control.

The drawing shows the block diagram of the device. 15

The device contains a methane concentration sensor 1, a correction link 2, an inertial link 3 with variable inertia, an inverter 4 signal polarity, an analog total of 20 torr 5, an executive unit 6 and an amplifier 7 with a dead zone.

The output of the correction link 2 is connected to the inverter input 4 of the signal polarity and to the input of the inertia ^ 5 link 3 with variable inertia, the output of the latter is connected to the executive unit bis by the first input of the analog adder 5. The second input of the analog adder 5 the polarity of the signal, and the output of the analog adder 5 is connected to the input of the amplifier 7 with a dead zone. The output of the amplifier 7 with the dead zone is connected to the control input of the inertial link 3 with variable inertia.

The methane concentration sensor 1 serves to convert a non-electric quantity — methane concentration into an electrical analog signal.

In sensor 1, the concentration of methane can be used, for example, thermochemical or thermoconduction primary transducer. Corrective element 2 is designed to accelerate the determination of the steady-state value of methane concentration during its measurement by inertia sensors and is, for example, an operational amplifier with a differentiating and summing circuits. The inertial unit 3 with variable inertia is in its simplest form an integrating X-Chain with variable external influence by the values of resistance, capacitance, or both. Analog adder 5 implements the function of algebraic addition of two analog signals. The amplifier 7 with the deadband can be implemented, for example, using an operational amplifier, the output of which is constant (unchanged) when the signal at the input changes to a certain level (the operational amplifier is in the saturation region). When this level is exceeded, the signal at the output of the operational amplifier changes in proportion to the signal at the input (the operational amplifier is in the linear region).

The device works as follows.

An electrical analog signal from sensor 1 of methane concentration is fed to the input of the correction link 2, which in the simplest case performs the differentiation of this signal and its summation in a certain proportion with the derived derivative. The adjusted analog signal is fed to the analog adder in two ways: through the invertor 4 of the polarity of the signal and through the inertial link 3 with variable inertia. The total signal is fed to the input of the amplifier 7 with a dead zone. Depending on the magnitude of this signal, the amplifier 7 generates a control action for the inertial link 3 with variable inertia.

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In the static mode, when the signal from sensor 1 of methane concentration is constant or slowly changing, the voltage at the output of analog adder 5 is small and is outside the sensitivity zone of amplifier 7, therefore the signal at its output is constant and has a value at which the inertia element with variable inertia has a maximum a constant time t _max = (Κθ _{"ΑΚ <.} (where K and C values of the equivalent resistance and capacitance of the inertial unit). The value of ^< 'selected from _MDX-optimal conditions in the control concentr tion of methane in seams with a calm gas evolution. The value deadband amplifier 7 may, e.g., be mounted on its supply input and the reference voltage _0. It is determined on the basis of

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permissible dynamic error of control.

In the dynamic mode, the signal at the output of the correction link 2 grows faster than at the output of the inertia link 3 with variable inertia. As a result, the total voltage at the input of the amplifier 7 exceeds the threshold of the insensitivity zone, with this it goes into a linear region. The control signal generated by the amplifier 7 reduces the time constant of the inertial link 3 with variable inertia to a value, 5, at which the rate of change of the signal at its output is equalized with the rate of change of the signal at the output of the correction link 2. At the output of the analog adder 5 The signal is given with the level necessary to maintain the control action corresponding to the changed time constant. Due to the fact that the executive unit supplies 25 keys to the output of the inertial link 3 with variable inertia, its response time depends on the inertia of link 3 and, consequently, from the dynamics of methane concentration change at the installation location of sensor 1. In this sense The device is an adapter; to changing conditions of gas supply ·

The advantages of the proposed device for the automatic control of methane for coal mines are that the device is insensitive to short-term bursts of methane concentration and electrical interference, whose amplitude is less than the dead band of amplifier 7; interference, the amplitude of which exceeds the width of the dead zone, penetrating to the input of the execution unit, is reduced in level by the value of the width of the dead zone; The device can be used as a universal means of automatic control of methane in coal mines, regardless of their gas category.

Claims (1)

Claim An automatic methane monitoring device for coal mines, containing a methane concentration sensor, a correction link connected to its output, and an executive unit, characterized in that, in order to increase speed and reliability of control, it is equipped with a signal polarity inverter, inertia element with variable inertia, analog adder. And an amplifier with a dead zone, with the output of the corrective element connected to the combined inputs of the polarity inverter signal and the inertial Even with variable inertia, the output of which is connected to the input of the executive unit and the first input of the analog adder, the output of the signal polarity inverter is connected to the second input of the analog adder, the output of which is connected to the input of the amplifier with the dead zone, the output of which is connected to the inertia variable.