JPS59126259A - Apparatus for monitoring ventilation state and temperature - Google Patents

Abstract

PURPOSE:To perform the monitoring a ventilation state and a temp., by a method wherein an upper limit temp. setting variable resistor is assembled in a bridge having a temp. detecting thermistor and a reference thermistor assembled in two arms thereof and the bridge output is subjected to differential amplification to operate a switching circuit. CONSTITUTION:A bridge 2 receives a constant-current from a DC constant-current power source 1 and outputs voltage corresponding to the change in the temp. of combustion air. The output voltage of the bridge 2 is supplied to a switching circuit 4 through a differential amplifier 3 and the transistor 41 of the circuits 4 performs the opening and closing control of the contact of a relay 42. In the bridge 2, a thermistor 21 for detection is provided to the air flowline of an incinerator in an exposed state while a reference thermistor 22 is provided to the outside of an object to be measured of the air flowline. A fixed resistor 23 is connected to the thermistor 20 in series and a temp. setting variable resistor 24 has a resistance value equal to that of the resistor 23 and sets the temp. limit value of combustion air during the normal operation of the incinerator. By this method, a ventilation state and a temp. are monitored to enable the control of an external apparatus.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a ventilation status and temperature monitoring device for monitoring and determining ventilation status and temperature of combustion air in burners, boilers, incinerators, etc. be.

BACKGROUND TECHNOLOGY Conventional devices of this type are often used as measuring instruments to measure wind speed or temperature individually, or to determine the ventilation condition of combustion air or set a limit temperature, etc. for that temperature. There was nothing that would make it work.

In addition, conventional wind speed measuring instruments use a thermal lightning pair as a detector.

Resistors, thermistors, etc. are used, but both methods require the temperature of the detection part to be 100°C in order to detect the third speed.
This is done by heating with a heater and taking advantage of the heat dissipation effect of the wind. For this reason, the power consumption was high and the device could not be made smaller.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a ventilation condition and temperature monitoring device for monitoring the ventilation condition and temperature of combustion air in burners, boilers, incinerators, etc., and performing necessary control.

To achieve this objective, the device of the present invention is configured to detect the ventilation status and temperature using a combination of a simple sensor and a differential amplifier, and can also detect when the temperature exceeds a set value. did.

According to the present invention, it is possible to immediately know not only when the temperature of the combustion air rises too much, but also when the ventilation stops, and furthermore, it does not require a heater, and provides a small device with low power consumption. can.

BEST MODE FOR CARRYING OUT THE INVENTION Next, the embodiments of the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the ventilation condition and temperature monitoring device of the present invention. 1 is a DC constant current power supply, 2 is a bridge that receives a constant current from the DC constant current power supply 1 and outputs a voltage corresponding to a change in the temperature of the combustion air, and 3 is a differential amplifier that differentially amplifies the output voltage of bridge 2. Dynamic amplifier, 4 is a switching circuit with a switching transistor 41 and a relay 4
The transistor 41 is driven by the output of the differential amplifier 3, and when the output of the differential amplifier 3 becomes less than a predetermined value (for example, about 0.7 V), the relay 42 becomes de-energized.
Performs switching operation. Reference numeral 5 denotes a DC stabilized power supply that supplies a constant voltage to the DC constant current power supply 1 and the switching circuit 4. Reference numeral 6 denotes a controlled device, such as a motor that drives a pump that feeds fuel to a burner.

Reference numeral 21 denotes a detection thermistor, which is installed, for example, in an exposed state in the ventilation flow path of an incinerator, and measures the temperature. 22 is a reference thermistor placed outside the object to be measured or outside the ventilation flow path; 23 is a fixed resistor connected in series with the detection thermistor; 2
Reference numeral 4 denotes a variable resistor for setting an upper limit temperature, which has a resistance value equal to the fixed resistor and sets a limit value of the combustion air temperature during normal operation of the furnace. N1 is the detection thermistor 21 and fixed resistor 23
N2 is the node between the reference thermistor 22 and the upper limit temperature setting variable resistor 24, T1 is the detection thermistor 21
．． The phase current passing through the fixed resistor 23 side, T2, is the reference thermistor 22. This is a phase current passing through the upper limit temperature setting variable resistor 24 side. T1. T2 is the output terminal of bridge 2.

Next, the operation of this circuit will be explained.

When the operation of the incinerator is stopped and the ambient temperature of the monitoring device is at room temperature, the four sides of the bridge 2 satisfy the equilibrium condition, so when a constant current is supplied from the DC constant current power source 1, the node N+
, N2 are at the same potential.

Now the slide of the variable resistor 24 for setting the upper limit temperature is at node N2.
If the cylinder is coming to the side, the output 1 of the differential amplifier 3-,
It has become 1 zero. Next, as you move the slide toward the ground side, the potential of terminal T2 (slide) becomes lower than that of terminal T1 (N1), so the output of differential amplifier 33 has positive polarity and its value gradually increases. . When the voltage reaches a predetermined value (for example, approximately 0.7V), the switching transistor 4.1 becomes conductive and the relay 42 is energized.

The upper limit humidity setting variable resistor 24 is set so that the relay 42 is set to @JVA when the temperature is normal and there is no wind.

In this state, ventilation of combustion air into the furnace is started, and the combustion air at room temperature is applied only to the detection thermistor 21. Since the temperature coefficient of resistance of the thermistor is negative, the resistance value of the detection thermistor 21 cooled by the combustion air increases,
The value of phase current ■1 decreases. Phase current 11. Since the sum of i2 is constant, a decrease in phase current 11 results in an increase in phase current 2. Regarding the potential, the potential at node N1 decreases, and the potential at node N1 decreases.
The potential of 2 increases. The increase in the potential of node N2 is due to the increase in the potential of node N2.
As the velocity of the combustion air increases, the potential at terminal T1 further decreases, the potential at terminal T2 further increases, and the potentials of each other are reversed, so that the output of differential amplifier 3 becomes The polarity becomes negative and the switching transistor 41 becomes non-conductive.

Thus, at normal operating speeds of combustion air, the base of switching transistor 41 is sufficiently biased in the non-conducting direction.

Next, when the incinerator starts normal operation, the velocity of the combustion air is the same as that of normal operation, and its temperature gradually increases from room temperature. Since the temperature of the combustion air exerts an effect on the detection thermistor 21 that is completely opposite to the velocity, as the temperature rises, the potential at the terminal T1 increases and the potential at the terminal T2 decreases.

When reversed, the output of the differential amplifier 3 gradually approaches zero volts from a negative polarity value. However, since the variable resistor 24 for setting the upper limit temperature is set so that the potential at the terminal T1 is lower than the potential at the terminal T2 when both the temperature and velocity of the combustion air are normal, the output of the differential amplifier 3 is zero. 1 Helangistor 41 for switching which is lower than the voltage
is non-conducting.

If the combustion air stops flowing for some reason during the operation of the incinerator, the temperature in the ventilation passage will rise rapidly, and the detection thermistor 2
The resistance value of 1 decreases rapidly. ”, the potential of the terminal T1 becomes greater than the potential of the terminal T2. Therefore, the output of the differential amplifier 3 becomes positive and the switching transistor 4
1 becomes conductive and the relay 42 is energized.

As mentioned above, the monitoring device of the present invention is capable of: (1) when the ventilation stops immediately after the incinerator starts operating when the combustion air is at room temperature; (2) when the combustion air stops after a long time has passed since the incinerator starts operating; Three cases can be distinguished: (1) when the ventilation stops when the temperature of the combustion air is sufficiently high; (2) when the combustion air velocity is normal but the temperature rises too much;

FIG. 2 shows the output of the bridge of the circuit of FIG. Vl indicates a potential change at the T1 terminal when combustion air is flowing, and vl - indicates a potential change at the T1 terminal when this air does not flow. V2 is the potential change of the slide terminal T2 of the variable resistor for setting the upper limit humidity. As mentioned in the explanation of Figure 1, since this bridge is driven by a constant current, Vl, Vl-, and V2' change in opposite ways as the temperature of the combustion air increases. Intersection P.

produces Q. . And P is the abnormality detection point at room temperature,
Q is the abnormality detection point during normal operation. When the temperature rises above the respective intersection points, the output of the differential amplifier 3 becomes positive,
Relay 42 is energized.

Note that the detection thermistor 21 and the reference thermistor 22 in this embodiment may be a composite of a resistor and a thermistor.

As explained above, the monitoring device of the present invention applies a constant current to a bridge composed of thermistors on two sides, and performs switching by amplifying the voltage output from the bridge with a differential amplifier according to changes in the temperature of combustion air. By operating the circuit, it is now possible to monitor ventilation conditions and humidity, and to control external equipment by opening and closing relays. When applied to incinerators, etc., it is possible to automatically control, prevent overheating,
Measures against incomplete combustion can now be taken, and the safety of operating incinerators and the like can be greatly improved.

Furthermore, by connecting a meter to the differential amplifier 3, it has become possible to visually observe changes in the temperature of the combustion air.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of an embodiment of the ventilation status and temperature monitoring device of the present invention, and Figure 2 is the output terminal T of the bridge in Figure 1.
FIG. 1 is a diagram showing potential changes of T1 and T2. 1...DC constant current power supply, 2...Bridge, 3...Differential amplifier, 4...Switching circuit, 5...Stabilization Power supply, 6...Controlled device, 21...Detection thermistor, 22...Reference thermistor, 23...Fixed resistor, 24...・・Variable resistor for upper limit temperature setting. Applicant Nippon Electric Seiki Co., Ltd. Agent Patent Attorney Masu 1) Takeo

Claims (1)

[Claims] 1. A DC constant current power supply, a bridge to which a constant current input is given from the DC constant current power supply, a differential amplifier that inputs the potential of the two output terminals of the bridge and differentially amplifies it, and the differential amplifier. The relay contacts switch according to the output value of the! ! 1, and the four sides of the bridge include a detection thermistor for detecting temperature, and a reference thermistor having characteristics equal to the resistance-temperature characteristics of the detection thermistor. A ventilation condition and humidity monitoring device comprising: a fixed resistor connected in series with the test thermistor; and a variable resistor for setting an upper limit temperature, connected in series with the reference thermistor and having a resistance value equal to the fixed resistor.