A thermistor liquid level signal circuit with temperature compensation

Abstract

The present invention proposes a thermistor-type liquid level signal circuit with temperature compensation. By setting a first temperature compensation circuit and a second temperature compensation circuit, when the liquid level signal is in low-temperature air, the switch module input signal is compensated to a low-voltage signal, triggering an alarm signal. When the liquid level signal is in high-temperature fuel, the switch module input signal is compensated to a high-voltage signal, and no alarm signal is triggered. By adding an additional temperature compensation resistor, when the external ambient temperature changes drastically, the temperature compensation resistor can be used to adjust the voltage value of the collection point, so that the voltage of the collection point changes in the opposite direction, thereby improving the adaptability of the thermistor liquid level sensor to the environment and compensating for the impact of external environmental changes. The structure is simple and reliable, the functions are more complete, the adaptability of the thermistor liquid level sensor to the environment is improved, and the problem of false alarms of the liquid level sensor in extreme environments is solved.

Description

Technical Field

[0001] The invention relates to the field of liquid level monitoring, in particular to a thermistor type liquid level signal device circuit with temperature compensation. Background Art

[0002] Sensor technology is fundamental to measurement and control systems. Modern aircraft fuel measurement and control systems utilize a variety of sensors to measure various fuel properties and conditions. However, because these sensors operate within the fuel environment and the entire measurement and control system is complex and large, maintenance and repair are significantly inconvenient. Therefore, improving the reliability, maintainability, testability, and safety of fuel tank components is crucial for enhancing overall aircraft safety and economic efficiency. Sensors utilize a variety of circuits. Traditional thermistor-type level indicators lack temperature compensation and are poorly adaptable to environmental conditions, leading to false alarms in extreme environments. While the level indicator should trigger an alarm when exposed to cold air, conventional thermistor-type level indicators may not, potentially leading to misjudgment by the crew and compromising flight safety. Furthermore, when exposed to hot fuel, the level indicator should not trigger an alarm, but conventional thermistor-type level indicators may generate false alarms, potentially leading to misjudgment by the crew and compromising flight safety. Summary of the Invention

[0003] In view of the problem that traditional thermal liquid level signal detectors in the prior art have poor adaptability to the environment and may give false alarms in extreme environments, the present invention proposes a thermistor liquid level signal detector circuit with temperature compensation. By setting a first temperature compensation circuit and a second temperature compensation circuit, when the liquid level signal detector is in low-temperature air, the input signal of the switch module is compensated to a low-voltage signal, triggering an alarm signal. When the liquid level signal detector is in high-temperature fuel, the input signal of the switch module is compensated to a high-voltage signal, and no alarm signal is triggered. This improves the adaptability of the thermal liquid level sensor to the environment and solves the problem of false alarms of the liquid level sensor in extreme environments.

[0004] The specific implementation contents of the present invention are as follows:

[0005] A thermistor type liquid level signal circuit with temperature compensation, comprising a temperature compensation liquid level sensing circuit and an alarm circuit connected in sequence;

[0006] The temperature compensation liquid level sensing circuit includes a liquid level sensor and a first temperature compensation circuit;

[0007] The alarm circuit includes a second temperature compensation circuit, a switch module, and an alarm;

[0008] The first temperature compensation circuit and the second temperature compensation circuit are connected in series, and the liquid level sensor is connected in parallel with the first temperature compensation circuit and the second temperature compensation circuit, which are connected in series, for displaying the liquid level;

[0009] The first temperature compensation circuit and the second temperature compensation circuit connected in series are connected to the switch module and are used to compensate for the input voltage of the switch module. When the liquid level signaler is in low-temperature air, the input signal of the compensation switch module is a low-voltage signal, triggering the alarm to output an alarm signal. When the liquid level signaler is in high-temperature fuel, the input signal of the compensation switch module is a high-voltage signal, and the alarm is not triggered.

[0010] In order to better implement the present invention, further, the first temperature compensation circuit includes temperature compensation resistors RT2 and R3 connected in parallel with each other, which are used to output a low voltage signal to the switch module when the temperature drops and output a high voltage signal to the switch module when the temperature rises.

[0011] In order to better implement the present invention, further, the second temperature compensation circuit includes a resistor R4 and a thermistor RT3 connected in parallel with each other;

[0012] The resistor R4 and thermistor RT3 connected in parallel are connected between the output end of the first compensation circuit and the output end of the liquid level sensor, and the weight of the thermistor RT3 in parallel with the resistor R4 is smaller than the weight of the temperature compensation resistor RT2 in parallel with the resistor R3.

[0013] In order to better implement the present invention, further, the switch module includes a first switch module and a second switch module;

[0014] The first switch module is connected to the second temperature compensation circuit, the power supply, and the second switch module, and is used to receive the low voltage signal of the first temperature compensation circuit, control the first switch module to be turned off and the second switch module to be turned on, and trigger the alarm to output an alarm signal; and is used to receive the high voltage signal of the first temperature compensation circuit, control the first switch module to be turned on and the second switch module to be turned off, and not trigger the alarm.

[0015] In order to better implement the present invention, further, the first switch module includes a transistor VT1; the second switch module includes a transistor VT2;

[0016] The base of the transistor VT1 is connected between the output terminal of the first temperature compensation circuit and the input terminal of the second temperature compensation circuit, the collector is connected to the power supply VCC, and the emitter is connected to the ground terminal;

[0017] The base of the transistor VT2 is connected between the power supply VCC and the collector of the transistor VT1, the emitter is connected between the emitter of the transistor VT1 and the ground, and the collector is connected to the power supply and the alarm.

[0018] In order to better implement the present invention, further, the first switch module further includes a first protection circuit; the second switch module further includes a second protection circuit;

[0019] The first protection circuit includes a resistor R6, and the resistor R6 is connected between the collector of the transistor VT1 and the power supply VCC;

[0020] The second protection circuit includes a resistor R7 connected between the collector of the transistor VT2 and the power supply VCC.

[0021] In order to better implement the present invention, further, the switch module further includes a resistor R5;

[0022] One end of the resistor R5 is connected between the emitter of the transistor VT1 and the emitter of the transistor VT2, and the other end is connected between the liquid level sensor and the ground. The resistance of the resistor R5 is much smaller than the resistance of the resistor R6 and the resistor R7.

[0023] In order to better implement the present invention, further, the degree compensation liquid level sensing circuit further includes a resistor R1 and a resistor R2 connected in parallel with each other;

[0024] The input ends of the resistors R1 and R2 connected in parallel are connected to the power supply VCC, and the output ends are connected to the first temperature compensation circuit and the liquid level sensor respectively.

[0025] In order to better implement the present invention, further, the liquid level sensor includes a thermistor RT1, and the temperature coefficient of the thermistor RT1 is higher than the temperature coefficient of the thermistor RT3.

[0026] The present invention has the following beneficial effects:

[0027] (1) The present invention adds an additional temperature compensation resistor to the liquid level signal circuit. When the external ambient temperature changes drastically, the voltage value of the collection point can be adjusted by the temperature compensation resistor, so that the voltage of the collection point changes in the opposite direction, thereby compensating for the impact of the external environment change;

[0028] (2) The thermistor-type liquid level signal circuit with temperature compensation proposed in the present invention has a simple and reliable structure and more complete functions, which improves the adaptability of the thermistor-type liquid level sensor to the environment and solves the problem of false alarms of the liquid level sensor in extreme environments;

[0029] (3) The present invention uses the thermistor RT1 as the sensing end of the fuel alarm, which has a high temperature coefficient and is sensitive to temperature changes. When the thermistor RT1 is exposed to the oil surface, an alarm signal is triggered to remind the crew that the fuel has reached a preset position; when the thermistor RT1 is not exposed to the oil surface, no alarm signal is triggered. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a module connection diagram of the present invention;

[0031] Figure 2 This is the circuit schematic diagram of a liquid level signal device with temperature compensation thermistor value. DETAILED DESCRIPTION

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. It should be understood that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, and therefore should not be regarded as limiting the scope of protection. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technical personnel in this field without making creative work are within the scope of protection of the present invention.

[0033] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0034] Example 1:

[0035] This embodiment proposes a thermistor type liquid level signal circuit with temperature compensation, such as Figure 1 As shown, it includes a temperature compensation liquid level sensing circuit and an alarm circuit connected in sequence;

[0036] The temperature compensation liquid level sensing circuit includes a liquid level sensor and a first temperature compensation circuit;

[0037] The alarm circuit includes a second temperature compensation circuit, a switch module, and an alarm;

[0038] The first temperature compensation circuit and the second temperature compensation circuit are connected in series, and the liquid level sensor is connected in parallel with the first temperature compensation circuit and the second temperature compensation circuit, which are connected in series, for displaying the liquid level;

[0039] The first temperature compensation circuit and the second temperature compensation circuit connected in series are connected to the switch module and are used to compensate for the input voltage of the switch module. When the liquid level signaler is in low-temperature air, the input signal of the compensation switch module is a low-voltage signal, triggering the alarm to output an alarm signal. When the liquid level signaler is in high-temperature fuel, the input signal of the compensation switch module is a high-voltage signal, and the alarm is not triggered.

[0040] Working principle: In this embodiment, by setting the first temperature compensation circuit and the second temperature compensation circuit, when the liquid level signal device is in low-temperature air, the input signal of the compensation switch module is a low-voltage signal, which triggers an alarm signal. When the liquid level signal device is in high-temperature fuel, the input signal of the compensation switch module is a high-voltage signal, which does not trigger an alarm signal. This improves the adaptability of the thermal liquid level sensor to the environment and solves the problem of false alarms of the liquid level sensor in extreme environments.

[0041] Example 2:

[0042] This embodiment is based on the above embodiment 1. Figure 2 As shown, the specific structure of the temperature compensation liquid level sensing circuit and the alarm circuit is described.

[0043] Working principle: The first temperature compensation circuit includes a temperature compensation resistor RT2 and a resistor R3 connected in parallel, which are used to output a low voltage signal to the switch module when the temperature drops and output a high voltage signal to the switch module when the temperature rises.

[0044] The second temperature compensation circuit includes a resistor R4 and a thermistor RT3 connected in parallel with each other;

[0045] The resistor R4 and thermistor RT3 connected in parallel are connected between the output end of the first compensation circuit and the output end of the liquid level sensor, and the weight of the thermistor RT3 in parallel with the resistor R4 is smaller than the weight of the temperature compensation resistor RT2 in parallel with the resistor R3.

[0046] The switch module includes a first switch module and a second switch module;

[0047] The first switch module is connected to the second temperature compensation circuit, the power supply, and the second switch module, and is used to receive the low voltage signal of the first temperature compensation circuit, control the first switch module to be turned off and the second switch module to be turned on, and trigger the alarm to output an alarm signal; and is used to receive the high voltage signal of the first temperature compensation circuit, control the first switch module to be turned on and the second switch module to be turned off, and not trigger the alarm.

[0048] The first switch module includes a transistor VT1; the second switch module includes a transistor VT2;

[0049] The base of the transistor VT1 is connected between the output terminal of the first temperature compensation circuit and the input terminal of the second temperature compensation circuit, the collector is connected to the power supply VCC, and the emitter is connected to the ground terminal;

[0050] The base of the transistor VT2 is connected between the power supply VCC and the collector of the transistor VT1, the emitter is connected between the emitter of the transistor VT1 and the ground, and the collector is connected to the power supply and the alarm.

[0051] The first switch module further includes a first protection circuit; the second switch module further includes a second protection circuit;

[0052] The first protection circuit includes a resistor R6, and the resistor R6 is connected between the collector of the transistor VT1 and the power supply VCC;

[0053] The second protection circuit includes a resistor R7 connected between the collector of the transistor VT2 and the power supply VCC.

[0054] The switch module further includes a resistor R5;

[0055] One end of the resistor R5 is connected between the emitter of the transistor VT1 and the emitter of the transistor VT2, and the other end is connected between the liquid level sensor and the ground. The resistance of the resistor R5 is much smaller than the resistance of the resistor R6 and the resistor R7.

[0056] In order to better implement the present invention, further, the degree compensation liquid level sensing circuit further includes a resistor R1 and a resistor R2 connected in parallel with each other;

[0057] The input ends of the resistors R1 and R2 connected in parallel are connected to the power supply VCC, and the output ends are connected to the first temperature compensation circuit and the liquid level sensor respectively.

[0058] The liquid level sensor is a thermistor RT1 , and the temperature coefficient of the thermistor RT1 is higher than the temperature coefficient of the thermistor RT3 .

[0059] The rest of this embodiment is the same as that of the above-mentioned embodiment 1, and therefore will not be described in detail.

[0060] Example 3:

[0061] This embodiment is based on any one of the above embodiments 1-2. Figure 2 As shown in the figure, the working principle of the liquid level signal device in four environments: normal temperature air, low temperature air, normal temperature fuel, and high temperature fuel is explained in detail.

[0062] Working Principle: The circuit consisting of resistors R1, R2, R3, temperature compensation resistor RT2, and thermistor RT1 is placed in the fuel. Thermistor RT1 acts as the fuel alarm sensor. When thermistor RT1 is above the fuel level, an alarm signal is triggered, alerting the crew that the fuel has reached the preset level. When thermistor RT1 is below the fuel level, no alarm signal is triggered. Resistors RT1 and RT3 are thermistors, and resistor RT2 is the temperature compensation resistor.

[0063] In this embodiment, the thermistor RT1 is required to be a high temperature coefficient resistor and is required to be sensitive to temperature changes; the transistor can be an ordinary transistor, preferably a switching transistor; there is no special requirement for other temperature compensation resistors and resistors.

[0064] Resistors R1 and R2 are connected in parallel to divide the voltage with thermistor RT1. Because thermistor RT1 has a lower resistance at high temperatures, the current flowing through the circuit of resistors R1, R2, and thermistor RT1 is relatively high, causing resistors R1 and R2 to have a slightly higher power than the other resistors. Connecting them in parallel can reduce the current flowing through a single resistor, further reducing its power. This allows for the use of smaller resistors with lower power and size, which is more conducive to product implementation. Using a single high-power resistor is also acceptable.

[0065] 1) When the liquid level signal is in normal temperature air, the heat dissipation in the air is slow, the temperature on the thermistor RT1 is high and the resistance is small. After voltage division, the voltage at point A is relatively low. After passing through the parallel network composed of resistor R3 and temperature compensation resistor RT2, the voltage at point B is also relatively low, which cannot drive transistor VT1 to conduct, but makes transistor VT2 conduct, triggering the alarm to generate an alarm signal;

[0066] 2) When the liquid level indicator is in the fuel at room temperature, the temperature of the thermistor RT1 is relatively low and the resistance is relatively large due to the rapid heat dissipation in the fuel. After voltage division, the voltage at point A is relatively high. After passing through the parallel network of resistor R3 and temperature compensation resistor RT2, the voltage at point B is also relatively high, causing transistor VT1 to conduct and transistor VT2 to cut off, thus not triggering the alarm to generate an alarm signal.

[0067] 3) When thermistor-type liquid level signaler is in low-temperature air, it should also trigger the alarm normally. However, ordinary thermistor-type liquid level signaler may not trigger the alarm, which may cause the crew to make misjudgments and affect flight safety. However, thermistor-type liquid level signaler with temperature compensation can still trigger the alarm normally in low-temperature air. The principle is as follows:

[0068] When the temperature of thermistor RT1 is relatively low, its resistance is relatively large. After voltage division, the voltage at point A is relatively high. At the same time, the temperature of temperature compensation resistor RT2 is also relatively low, and its resistance is also relatively large. The total resistance of temperature compensation resistor RT2 in parallel with resistor R3 is larger than the total resistance of temperature compensation resistor RT2 in parallel with resistor R3 at room temperature. In this way, the voltage drop between A and B is larger than the voltage drop between A and B at room temperature. As a result, the voltage at point B is relatively small and cannot drive transistor VT1 to turn on. Instead, transistor VT2 is turned on, triggering the alarm to generate an alarm signal. In this way, in a low-temperature environment, the change in resistance of thermistor RT1 with temperature is compensated by temperature compensation resistor RT2. After compensation, the alarm can be triggered normally to generate an alarm signal in a low-temperature environment.

[0069] RT3 is a thermistor that also plays a role in temperature compensation. When the ambient temperature is relatively low, its resistance is also relatively large. The total resistance of thermistor RT3 in parallel with resistor R4 is larger than the total resistance of thermistor RT3 in parallel with resistor R4 at room temperature. However, the increased resistance of thermistor RT3 in parallel with resistor R4 at low temperature is smaller than the increased resistance of the temperature compensation resistor RT2 in parallel with resistor R3 at low temperature. That is, the weight of the temperature compensation resistor RT2 in parallel with resistor R3 at low temperature is greater than the weight of the thermistor RT3 in parallel with resistor R4 at low temperature. The combined effect still makes the voltage at point B relatively low, unable to drive transistor VT1 to turn on, but causes transistor VT2 to turn on, triggering the alarm normally.

[0070] Therefore, when the temperature of thermistor RT1 is relatively low, the voltage at point A is higher, and the voltage at point B should also be higher. However, through the combined effect of temperature compensation resistor RT2 and thermistor RT3, the voltage at point B is lower than that at room temperature, causing transistor VT1 to be cut off and transistor VT2 to be turned on, normally triggering the alarm to generate an alarm signal.

[0071] 4) When a thermistor-type liquid level indicator is in high-temperature fuel, it should not trigger the alarm to generate an alarm signal. However, ordinary thermistor-type liquid level indicators may produce false alarms, which may cause the crew to make misjudgments and affect flight safety. However, a thermistor-type liquid level indicator with temperature compensation can still avoid triggering the alarm to generate an alarm signal in high-temperature fuel. The principle is as follows:

[0072] When the temperature of thermistor RT1 is relatively high, its resistance is relatively small. After voltage division, the voltage at point A decreases. At the same time, the temperature of temperature compensation resistor RT2 is also relatively high, and its resistance is also relatively small. The total resistance of temperature compensation resistor RT2 in parallel with resistor R3 is smaller than the total resistance of temperature compensation resistor RT2 in parallel with resistor R3 at room temperature. In this way, the voltage drop between A and B is smaller than the voltage drop between A and B at room temperature. As a result, the voltage at point B is relatively large, which can drive transistor VT1 to conduct and transistor VT2 to cut off, and will not trigger the alarm device to generate an alarm signal. In this way, in high-temperature fuel, the change in the resistance of thermistor RT1 with temperature is compensated by temperature compensation resistor RT2, and after compensation, the alarm will not be triggered in high-temperature fuel.

[0073] RT3 is a thermistor, which also plays the role of temperature compensation. When the temperature in the fuel tank is relatively high, the resistance is relatively small. The total resistance of the thermistor RT3 in parallel with the resistor R4 is smaller than the total resistance of the thermistor RT3 in parallel with the resistor R4 at room temperature. However, the resistance reduced by the thermistor RT3 in parallel with the resistor R4 at high temperature is greater than the resistance reduced by the temperature compensation resistor RT2 in parallel with the resistor R3 at high temperature. As a result, the voltage at point B is still relatively high, which can drive the transistor VT1 to turn on and the transistor VT2 to turn off, and the alarm device will not be triggered to generate an alarm signal.

[0074] Therefore, when the temperature of thermistor RT1 is relatively high, the voltage at point A is lower, and the voltage at point B should also be lower. However, through the combined effect of temperature compensation resistor RT2 and thermistor RT3, the voltage at point B is higher than that at room temperature, causing transistor VT1 to turn on and transistor VT2 to turn off, and the alarm device will not be triggered to generate an alarm signal.

[0075] Resistor R6 is connected to the collector of transistor VT1, and resistor R7 is connected to the collector of transistor VT2, with the other end connected to the power supply voltage. Resistor R5 is connected to the emitters of transistors VT1 and VT2, with the other end grounded. They are used to limit the current flowing through transistors VT1 and VT2, respectively. When transistor VT1 is turned on, resistors R5 and R6 divide the voltage; when transistor VT2 is turned on, resistors R5 and R7 divide the voltage. Resistor R5 has a much smaller resistance than resistors R6 and R7, so the voltage divided by the upper end of resistor R5 can be ignored.

[0076] The rest of this embodiment is the same as any of the above embodiments 1-2, so it will not be repeated here.

[0077] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A thermistor type liquid level signal circuit with temperature compensation, characterized in that: It includes a temperature compensation liquid level sensing circuit and an alarm circuit connected in sequence; The temperature compensation liquid level sensing circuit includes a liquid level sensor and a first temperature compensation circuit; The alarm circuit includes a second temperature compensation circuit, a switch module, and an alarm; The first temperature compensation circuit and the second temperature compensation circuit are connected in series, and the liquid level sensor is connected in parallel with the first temperature compensation circuit and the second temperature compensation circuit, which are connected in series, for displaying the liquid level; The first temperature compensation circuit and the second temperature compensation circuit connected in series are connected to the switch module and are used to compensate the input voltage of the switch module. When the liquid level signal sensor is in low-temperature air, the input signal of the switch module is compensated to a low-voltage signal, triggering the alarm to output an alarm signal. When the liquid level signal sensor is in high-temperature fuel, the input signal of the switch module is compensated to a high-voltage signal, and the alarm is not triggered. The first temperature compensation circuit includes a temperature compensation resistor RT2 and a resistor R3 connected in parallel, and is used to output a low voltage signal to the switch module when the temperature decreases and output a high voltage signal to the switch module when the temperature increases; The second temperature compensation circuit includes a resistor R4 and a thermistor RT3 connected in parallel with each other; The resistor R4 and the thermistor RT3 connected in parallel are connected between the output end of the first compensation circuit and the output end of the liquid level sensor, and the weight of the thermistor RT3 in parallel with the resistor R4 is less than the weight of the temperature compensation resistor RT2 in parallel with the resistor R3; The switch module includes a first switch module and a second switch module; The first switch module is connected to the second temperature compensation circuit, the power supply, and the second switch module, and is used to receive a low voltage signal from the first temperature compensation circuit, control the first switch module to turn off, the second switch module to turn on, and trigger the alarm to output an alarm signal; and is used to receive a high voltage signal from the first temperature compensation circuit, control the first switch module to turn on, the second switch module to turn off, and not trigger the alarm; The first switch module includes a transistor VT1; the second switch module includes a transistor VT2; The base of the transistor VT1 is connected between the output terminal of the first temperature compensation circuit and the input terminal of the second temperature compensation circuit, the collector is connected to the power supply VCC, and the emitter is connected to the ground terminal; The base of the transistor VT2 is connected between the power supply VCC and the collector of the transistor VT1, the emitter is connected between the emitter of the transistor VT1 and the ground, and the collector is connected to the power supply and the alarm.

2. A thermistor type liquid level signal circuit with temperature compensation as claimed in claim 1, characterized in that: The first switch module further includes a first protection circuit; the second switch module further includes a second protection circuit; The first protection circuit includes a resistor R6, and the resistor R6 is connected between the collector of the transistor VT1 and the power supply VCC; The second protection circuit includes a resistor R7 connected between the collector of the transistor VT2 and the power supply VCC.

3. A thermistor type liquid level signal circuit with temperature compensation as claimed in claim 2, characterized in that: The switch module further includes a resistor R5; One end of the resistor R5 is connected between the emitter of the transistor VT1 and the emitter of the transistor VT2, and the other end is connected between the liquid level sensor and the ground. The resistance of the resistor R5 is much smaller than the resistance of the resistor R6 and the resistor R7.

4. A thermistor type liquid level signal circuit with temperature compensation as claimed in claim 1, characterized in that: The temperature compensation liquid level sensing circuit further includes a resistor R1 and a resistor R2 connected in parallel with each other; The input ends of the resistors R1 and R2 connected in parallel are connected to the power supply VCC, and the output ends are connected to the first temperature compensation circuit and the liquid level sensor respectively.

5. A thermistor type liquid level signal circuit with temperature compensation according to any one of claims 1 to 4, characterized in that: The liquid level sensor includes a thermistor RT1 , and a temperature coefficient of the thermistor RT1 is higher than a temperature coefficient of the thermistor RT3 .

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