JPH0448279B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an abnormality detector that captures changes in physical phenomena as changes in frequency and detects abnormalities based on the changes in frequency.

(Prior Art) Conventionally, a fire detector as shown in FIG. 3 has been proposed as a fire detector that detects a fire based on a change in frequency by detecting a change in temperature due to a fire as a change in frequency.

In Fig. 3, the detection unit 1 is provided with a time constant circuit in which a resistor R1 and a capacitor C1 are connected in series between a pair of power supply lines, and a heat-sensitive thyristor Ts is formed in parallel with the capacitor C1, as shown in Fig. 4. Assuming that the power is turned on when the ambient temperature is -10°C, the capacitor C1 is charged through the resistor R1 with a predetermined time constant, and when the charging voltage V _A reaches the predetermined voltage, that is, the break voltage of the thermal thyristor Ts. Make the heat-sensitive thyristor Ts conductive. The capacitor C1 is discharged by the conduction of the heat-sensitive thyristor Ts, and when the discharge current becomes equal to or less than the holding current of the heat-sensitive thyristor Ts, the heat-sensitive thyristor Ts is turned off. When the heat-sensitive thyristor Ts is turned off, the capacitor C1 is charged again. The oscillation operation continues in the same manner.

Here, if the ambient temperature gradually rises from -10℃, the heat-sensitive thyristor will respond to the rise in temperature.
Break voltage V _BO of Ts decreases. Therefore, the fourth
As shown in the figure, the charging time for charging the capacitor C1 becomes faster by the amount that the break voltage V _BO decreases, and the oscillation frequency increases. This oscillation output is given to the conversion circuit 2 to be converted into a temperature change, and the display circuit 3 is driven to display the temperature change.

(Problem to be solved by the invention) However, as the ambient temperature rises, the amplitude of the oscillation output decreases, and especially at the detection temperature at which fire is detected, the amplitude of the oscillation output decreases even further, making it difficult to detect frequency changes. However, it is difficult to detect fires, which increases errors and makes it impossible to detect fires with high accuracy.

(Means for Solving the Problems) The present invention has been made in view of the above problems, and aims to detect changes in physical phenomena, for example, temperature changes due to fire, in order to accurately detect changes in physical phenomena. A voltage conversion means detects a change and converts it into a change in a voltage signal, and a frequency conversion means converts a frequency based on a signal output from the voltage conversion means, and detects an abnormality based on the frequency change from the frequency conversion means. In the abnormality detector for detecting, the frequency conversion means includes a signal input terminal, and a limiting input terminal including an upper limit input terminal that limits the upper limit of the signal voltage input to the signal input terminal and a lower limit input terminal that limits the lower limit. A flip-flop circuit that sets or resets according to the signal output of the window comparator is provided, and the signal voltage from the voltage conversion means is applied to one limited input terminal of the window comparator, and a constant reference voltage is applied to the It is applied to the other limited input terminal of the window comparator, is feedback-connected from the output side of the flip-flop circuit to the signal input terminal of the window comparator via a predetermined charging/discharging circuit, and is further output from the other output side of the flip-flop circuit. a gate circuit that outputs signal pulses for a predetermined time determined by a reference time generator; a counter circuit that counts signal pulses input from the gate circuit during the predetermined time, converts them into A/D, and outputs them; The present invention is characterized in that it is provided with a display section that displays the detected value numerically based on the count signal from the counter circuit.

(Embodiment) FIG. 1 is a circuit diagram showing an embodiment of the present invention.

First, the configuration will be explained. 5 is a constant voltage power supply, which supplies a constant voltage to the circuit section. Reference numeral 16 denotes voltage conversion means, which includes a temperature sensor inside and converts temperature changes caused by a fire into voltage changes. Reference numeral 17 denotes a frequency conversion means, which converts the frequency based on the signal output from the voltage conversion means 16. 12 is a gate circuit; 13 is a reference time generating section; the reference time generating section 13 has a built-in oscillation circuit that oscillates at a predetermined _period ; oscillation pulses are output to the gate circuit 12. The gate circuit 12 outputs the signal pulse from the frequency conversion means 17 obtained during the pulse width t ₀ of the oscillation pulse from the reference time generator 13 to the counter circuit 14 . The counter circuit 14 counts the signal pulses from the gate circuit 12 obtained during a predetermined period of time, ie, t ₀ , converts them into A/D, and outputs them to the display section 15 . The display unit 15 numerically displays the detected temperature based on the count signal from the counter circuit 14.

Next, the internal configuration of the voltage conversion means 16 will be explained. Resistors R5 and R6 are connected in series between the power supply lines, and the divided voltage of the resistors R5 and R6 is applied to the non-inverting input terminal of the operational amplifier 7. A resistor R7, a variable resistor VR, and a transistor TR as a temperature sensor using a semiconductor element are connected in series between the power lines, and the connection point of the resistor R7 and variable resistor VR is connected to the inverting input terminal of the operational amplifier 7. Therefore, a constant current flows through transistor TR. The output terminal of the operational amplifier 7 is connected to the base of the transistor TR via a resistor R8. transistor
The TR outputs the temperature change caused by the fire to the frequency conversion means 17 as a change in the base-emitter voltage Vbe by reducing the barrier voltage of the PN junction in accordance with the temperature rise caused by the fire.

Next, the internal configuration of the frequency conversion means 17 will be explained. 8 is a first operational amplifier, 9 is a second operational amplifier, and the first operational amplifier 8 and the second operational amplifier 9 form a window comparator.
10 is a flip-flop circuit, which is set or reset according to the signal output from the window comparator. The lower limit input terminal P3 of the second operational amplifier 9 has a signal voltage from the voltage conversion means 16,
That is, a constant reference voltage Va higher than the signal voltage Vb is applied to the upper limit input terminal P1 of the first operational amplifier 8. The output terminal X of the flip-flop circuit 10 is feedback-connected to the signal input terminals P ₂ and P ₄ of the window comparator via a resistor R ₀ . Here, as a charging/discharging circuit, a resistor R ₀ and a capacitor C ₀ are connected in series, and charging or discharging is performed at a predetermined time constant.

FIG. 2 is a signal waveform diagram of each part of the embodiment of FIG. 1. The operation of the present invention will be explained with reference to FIG.

As shown in FIG. 2, when the power is turned on at an ambient temperature T1, an H level is output from the terminal X serving as the reset output of the flip-flop circuit 10, charging the capacitor _C0 via the resistor _R0 .
By charging the capacitor _C0 , the voltage Vc input to the signal input terminal _P4 gradually increases. When the voltage Vc becomes larger than the signal voltage Vb from the voltage conversion means 16, the second operational amplifier 9 performs a detection operation and outputs an H level to the output terminal S. Furthermore, capacitor C ₀
As charging progresses and the voltage Vc becomes larger than the reference voltage Va, the first operational amplifier 8 performs a detection operation and outputs an L level to the output terminal Q. Output terminal Q
The flip-flop circuit 10 performs an inverting operation upon the L level output of , and outputs the L level to X. Output terminal
With the L level output of , the capacitor C ₀ is discharged through the path of the capacitor C ₀ → resistor R ₀ → the ground terminal to which the flip-flop 10 is connected, and the voltage Vc starts to decrease. Therefore, as the voltage Vc becomes lower than the reference voltage Va, the output terminal Q of the first operational amplifier 8 instantly returns to the H level. Furthermore, the capacitor
As the discharge of _C0 progresses, the voltage Vc decreases with a predetermined time constant, and when the voltage Vc becomes lower than the signal voltage Vb from the voltage conversion means 16, the second operational amplifier 9 performs a detection operation and outputs the signal to the output terminal S. Outputs L level.
When the output terminal S outputs an L level, the flip-flop circuit 10 performs an inverting operation and outputs an H level to the output terminal X. At H level output of output terminal X, resistor R ₀
Charge the capacitor C ₀ again via . As capacitor C ₀ is charged, voltage Vc begins to rise. When the voltage Vc becomes larger than the signal voltage Vb from the voltage conversion means 16, the second operational amplifier 9 performs a detection operation and the output terminal S instantly returns to the H level. The oscillation operation continues in the same manner. That is, a constant reference voltage Va higher than the signal voltage Vb from the voltage conversion means 16 is applied to the upper limit input terminal P1 of the window comparator constituted by the first operational amplifier 8 and the second operational amplifier 9, and A signal voltage Vb from the voltage conversion means 16 is applied to the upper limit input terminal P3, and the input voltage Vc input to the signal input terminals P2 and P4 changes between voltages Va and Vb at a predetermined time constant. Oscillation operation continues according to changes in voltage Vc.

Next, if the temperature rises from T1 to T2,
The voltage between the base and emitter of the PN junction of the transistor TR as a temperature sensor decreases, and the base voltage, ie, Vb, increases. Reference voltage Va input to upper limit input terminal P1 of window comparator
is constant, and as the signal voltage Vb input to the lower limit input terminal P3 of the window comparator increases, the potential difference between the voltages Va and Vb narrows, and as a result,
Window comparator signal input terminals P2 and P
4. The fluctuation range of the voltage Vc input to 4 becomes narrower. Voltage
As the fluctuation period of Vc becomes faster, the number of signal pulses output from the flip-flop circuit 10 increases.
A signal pulse from the output terminal Y of the flip-flop circuit 10 is applied to the gate circuit 12 and output to the counter circuit 14 for a predetermined time t ₀ determined by the reference time generator 13 . The counter circuit 14
The signal pulses input from the gate circuit 12 during t ₀ are counted, A/D converted, and output to the display section 15 . The display section 15 numerically displays the temperature T2 based on the count signal from the counter circuit 14.

In the above embodiment, the reference time generator 13 is configured to output a reference pulse having a pulse width t ₀ that is sufficiently longer than the pulse period of the signal pulse from the flip-flop circuit 15. The reference pulse may be configured to output a reference pulse having a cycle sufficiently shorter than the pulse width of the pulse. That is, when a signal pulse from the flip-flop circuit 10 is input to the gate circuit 12,
The counter circuit 1 receives the reference pulse from the reference time generator 13 for a time equal to the pulse width of the input signal pulse.
4, and the temperature may be displayed on the display section 15 based on the count number of the counter circuit 14.

Further, in the above embodiment, the detected temperature is displayed numerically on the display unit 15, but a predetermined fire temperature threshold level may be set and a fire is displayed when the threshold level is exceeded. .

Further, in the above embodiment, a temperature sensor that outputs a signal voltage corresponding to a temperature rise due to a fire was used as the voltage conversion means 16, but a smoke sensor that detects smoke caused by a fire, a CO gas sensor that detects CO gas concentration, and a
Appropriate voltage conversion means for converting changes in physical phenomena such as gas sensors into changes in voltage is used.

In addition, in the embodiment of FIG. 1, the transistor TR
In this example, a PNP type transistor is used, but an NPN type transistor may also be used. That is, a resistor P7 and a variable resistor VR are connected in series between the emitter of the NPN type transistor TR and the ground, and a connection point between the resistor R7 and the variable resistor VR is connected to the lower limit input terminal P3 of the second operational amplifier 9. The connection point between the resistor R8 and the base of the transistor TR may be connected to the upper limit input terminal P1 of the first operational amplifier 8.

(Effects of the Invention) As described above, according to the present invention, there is provided a voltage conversion means for detecting a change in a physical phenomenon and converting it into a change in a voltage signal, and a frequency an abnormality detector that detects an abnormality based on a frequency change from the frequency conversion means, the frequency conversion means having a signal input terminal, and an upper limit of the signal voltage input to the signal input terminal; a window comparator having a limiting input terminal with an upper limit input terminal that limits the upper limit and a lower limit input terminal that limits the lower limit; and a flip-flop circuit that sets or resets according to the signal output of the window comparator,
A signal voltage from the voltage conversion means is applied to one limiting input terminal of the window comparator, a constant reference voltage is applied to the other limiting input terminal of the window comparator, and a predetermined charge/discharge circuit is activated from the output side of the flip-flop circuit. a gate circuit that is feedback-connected to the signal input terminal of the window comparator through the gate circuit, and further outputs the signal pulse output from the other output side of the flip-flop circuit for a predetermined time determined by the reference time generator; a counter circuit that counts signal pulses input during the predetermined time, A/D converts the signals, and outputs the signals;
Since a display unit is provided that displays the detected value numerically based on the count signal from the counter circuit, it can be interpreted as an increase in frequency in response to a rise in detected temperature, and the amplitude of the oscillation output of the frequency conversion means can be interpreted as an increase in frequency. can be kept constant at all times, so it is possible to reliably detect abnormalities by detecting temperature changes with high precision.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a signal waveform diagram of each part of FIG. 1, FIG. 3 is a circuit diagram showing a conventional embodiment, and FIG. FIG. 3 is a signal waveform diagram of FIG. 5... constant voltage power supply, 7... operational amplifier, 8...
First operational amplifier, 9... Second first operational amplifier, 10... Flip-flop circuit, 12... Gate circuit, 13... Reference time generating section, 14... Counter circuit, 15... Display section, R5, R6, R
7, R8, R ₀ ... Resistor, C ₀ ... Capacitor.

Claims (1)

[Scope of Claims] 1. A voltage conversion means that detects a change in a physical phenomenon and converts it into a change in a voltage signal, and a frequency conversion means that converts a frequency based on a signal output from the voltage conversion means, In an abnormality detector that detects an abnormality based on a frequency change from a frequency conversion means, the frequency conversion means includes a signal input terminal, an upper limit input terminal that limits the upper limit of the signal voltage input to the signal input terminal, and a lower limit that limits the signal voltage input to the signal input terminal. a window comparator equipped with a lower limit input terminal and a limited input terminal;
a flip-flop circuit that is set or reset according to the signal output of the window comparator, and applying the signal voltage from the voltage conversion means to one limited input terminal of the window comparator;
A constant reference voltage is applied to the other limiting input terminal of the window comparator, and the output side of the flip-flop circuit is feedback-connected to the signal input terminal of the window comparator via a predetermined charging/discharging circuit; a gate circuit that outputs a signal pulse output from one output side for a predetermined time determined by a reference time generator;
A counter circuit that counts signal pulses input from the gate circuit during the predetermined time period, A/D converts the signals, and outputs the signals; and a display section that displays the detected value numerically based on the count signal from the counter circuit. An anomaly detector characterized by: