JPS6349837Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a gas leak alarm system that centrally monitors gas leaks at each location via a transmission line from multiple locations where multiple gas leak detection sensors are installed. .

In conventional gas leak alarm systems, the output of a gas leak detection sensor is connected to a receiver by a separate transmission line. For this reason, when a plurality of gas leak detection sensors are provided, a corresponding number of transmission lines are required, which makes wiring work time-consuming and the configuration of the alarm system complicated.

In view of the above-mentioned points, this invention aims to provide a gas leak alarm system that has a simplified configuration and can perform gas leak monitoring more reliably.

This invention successfully achieves the above objectives,
Predetermined 3 methods corresponding to troubles and gas leaks
It is connected to the respective outputs of a plurality of gas leak detection sensors that output value-level signals, and transmits frequency-modulated high signals, low signals, and pulse signals corresponding to the three-value levels to a common transmission line. A plurality of transmitting means, a receiving circuit that receives a signal from the transmission line and determines the type of the signal, and an alarm circuit that forms at least a gas leak alarm signal according to the output of the receiving circuit. and a signal multiplexing means for electrically associating the plurality of transmitting means and the plurality of receiving means, and the output signals of the plurality of transmitting means are multiplexed. The gas leak alarm system is characterized in that it forms a multiplex transmission system gas leak alarm system that is received by the plurality of receiving means via the transmission line.

Examples to which this invention is applied will be described below with reference to the drawings.

FIG. 1 shows the circuit configuration of one transmitting means in this embodiment. Gas leak detection sensors (not shown) are arranged at locations where gas leak detection is to be performed, and each gas leak detection sensor is provided with a transmitting means. The output of the gas leak detection sensor is connected to the input terminal of this transmitting means. This gas leak detection sensor detects a specific gas concentration around the installation location,
When the concentration is below the allowable value, it outputs a signal indicating that it is in a normal state, and when it exceeds the allowable value, it outputs a signal indicating that there is a gas leak, and it also prevents troubles such as when the sensor drive power supply malfunctions. It outputs a signal indicating the state, and outputs a predetermined three-level signal corresponding to each of these states. Normally, the signal levels representing normal, trouble, and gas leak conditions are 6V, 0V, and 12V. 3
The value level determination circuit 1 receives the three-value level signal from the gas leak detection sensor described above through input terminals 9 and 10, and determines whether the signal level represents normal, trouble, or gas leak status. When a signal representing a gas leak state is input, a high (H) signal is output only from output terminal a of judgment circuit 1, and when a signal representing a normal state is input, an H signal is output only from output terminal b. When a signal representing a trouble state is output and a signal representing a trouble state is further input, an H signal is output only from output terminal c. The output from the output terminal a is connected to a pulse generation circuit 2, and the output of the pulse generation circuit 2 is further connected to a modulation circuit 3. Output terminal b
The output from is also connected to the modulation circuit 3. The output from the output terminal c is inverted via the inverting circuit 6 and then introduced into the impedance matching circuit 7. The high frequency generation circuit 4 generates a high frequency determined by the frequency from the oscillator 5, and this high frequency is guided to the modulation circuit 3 as a carrier wave. This oscillator 5 includes a mechanical filter, etc., and the oscillation frequency of the high frequency is selectively set by changing the resonance frequency of this mechanical filter. Also,
The pulse generation circuit 2 includes a reference oscillator, a multivibrator, etc. (not shown), and outputs a pulse signal having a predetermined period to the modulation circuit 3 when the input signal from the output terminal a is at H level. When the modulation circuit 3 receives this pulse signal, it outputs a pulse signal modulated by the high frequency in response to this pulse signal, and when it receives an H signal from output terminal b, it outputs a pulse signal modulated by the high frequency in response to the H signal. This circuit outputs a signal modulated by Also,
The output of the modulation circuit 3 is also connected to the impedance matching circuit 7. The output of the impedance matching circuit 7 is transmitted to a transmission line (not shown) from output terminals 11 and 12 via an impedance circuit 8 having a capacitor C and a resistor R connected in series. Impedance matching circuit 7 and impedance circuit 8
is provided to prevent interference when another transmitting means having the same configuration as described above is connected to the transmission line.

Such a transmitting means is provided for each installed gas leak detection sensor, and is connected to the modulation circuit 3.
The frequency of the high frequency wave, which is the carrier wave, is set individually. For example, frequencies such as 500Hz, 600Hz, etc. are assigned, and the period of the pulse signal is 0.5
It is set to about seconds. Furthermore, a transmission cable used for normal multiplex transmission is used for the transmission line.

The above-mentioned transmitting means are provided corresponding to a plurality of gas leak detection sensors, and these transmitting means are connected to a plurality of receiving means described later through a common transmission line to constitute a gas leak alarm system. . In addition, signal multiplexing means is provided to electrically associate each transmitting means with each receiving means, and this signal multiplexing means assigns a unique frequency to the carrier wave of the modulation circuit of each transmitting means, and A receiving circuit, which will be described later, of the receiving means corresponding to the means is configured by setting the frequency of the signal to be determined among the transmission signals from the transmission line to the above-mentioned unique frequency.

Next, FIG. 2 shows the circuit configuration of one receiving means in this embodiment.

The receiving circuit includes a frequency discrimination circuit 21 and a signal discrimination circuit 22, and receives a transmission signal from the transmission line and discriminates the type of the signal. The frequency discrimination circuit 21 is a circuit that includes a mechanical filter and the like and discriminates a signal to which a predetermined frequency is assigned from the signals inputted from the input terminals 30 and 31. The frequency to be discriminated is set by the resonant frequency of the built-in mechanical filter. The output of the transmission line is connected to input terminals 30, 31,
Signals from each of the transmitting means are superimposed on this transmission line and input to the frequency discrimination circuit 21. Only the signals discriminated by the frequency discrimination circuit 21 are guided to the signal discrimination circuit 22. Signal discrimination circuit 2
2 determines whether the input signal is a high (H) signal, a low (L) signal, or a pulse signal. Furthermore, an alarm circuit (not shown) is provided within the signal discrimination circuit 22. This alarm circuit generates a gas leak alarm signal and a trouble alarm signal in response to the discriminated signal. That is, when the discriminated signal is a pulse signal, an H signal is output as a gas leak alarm signal from output terminal d, and when the discriminated signal is an L signal, an H signal is output as a trouble alarm signal from output terminal e. . The output from output terminal d is for gas leak status display.
The output from the terminal e is led to the LED 24 for displaying trouble status. That is, the output terminal d is connected to the base of the transistor 25, and the collector of the transistor 25 is connected to the LED2.
4 and further led to a power supply terminal 29. Also, the emitter of the transistor 25 is a diode 3.
2 to the collector of the transistor 26 and led to the output terminal 34, the base of the transistor 26 is connected to the oscillation circuit 23, and the emitter of the transistor 26 is grounded. On the other hand, the output terminal e is connected to the base of the transistor 28, and the collector of the transistor 28 is connected to the LED 2.
7 and led to the output terminal 33,
It is further led to a power supply terminal 29, and the emitter of the transistor 28 is grounded. The oscillation circuit 23 repeatedly generates an H signal and an L signal at a predetermined period. Now, when a gas leak alarm signal is generated and an H signal is output from output terminal d, transistor 2
5 is turned on, the LED 24 blinks in accordance with the period of the signal oscillated from the oscillation circuit 23, and the gas leak status is displayed. Furthermore, when a trouble alarm signal is generated and an H signal is output from the output terminal e, the transistor 28 is turned on and the LED 2
7 lights up and a trouble condition is displayed. In addition,
Other output circuits, such as a buzzer circuit, can be connected to the output terminal 34 to expand the alarm system.

As described above, according to this invention, the 3-level signal from the gas leak detection sensor is transmitted to the receiving means by multiplex transmission using a frequency discrimination method, so the system can be configured by connecting the transmitting and receiving means only with multiplex transmission lines. A gas leak alarm system is obtained that can simplify the process and ensure gas leak monitoring.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the structure of the transmitting means in an embodiment of the invention, and FIG. 2 is a circuit diagram showing the structure of the receiving means in the same embodiment. 1... Three-level level determination circuit, 2... Pulse generation circuit, 3... Modulation circuit, 9, 10, 30, 31...
...Input terminal, 11, 12, 33, 34...Output terminal, 21...Frequency discrimination circuit, 22...Signal discrimination circuit.

Claims (1)

[Scope of utility model registration request] a plurality of gas leak detection sensors that output signals of predetermined three-value levels in response to each state of normality, trouble, and gas leakage; a plurality of transmitting means for transmitting a high signal, a low signal, and a pulse signal to a common transmission line in accordance with the value level; a receiving circuit for receiving the signal from the transmission line and determining the type of the signal; and a plurality of receiving means including an alarm circuit that forms at least a gas leak alarm signal in response to the output of the receiving circuit;
A gas leak alarm system comprising signal multiplexing means for electrically associating the plurality of transmitting means and the plurality of receiving means.