JPH01216416A - Temperature detector - Google Patents

Abstract

PURPOSE:To obtain a linear characteristic even in a non-linear heating resistor such as a thermistor, etc., by providing the non-linear heating resistor such as the thermistor, etc., and a change means to connect the resistor to a fixed resistor in series and to change and set the resistance value of the fixed resistor. CONSTITUTION:The output of a temperature range decision part 13 is set at a low level at an ordinary room temperature, and the output is supplied to the base of the transistor 30 of a range change means via a sampling part 19 and a sample and hold part 23. The transistor 30 is turned ON, and a transistor 28 is turned OFF, and the fixed resistor 9 becomes effective, and the fixed resistors 8 and 9 are connected in series to the thermistor 7, then, a linear temperature-output potential characteristic can be obtained in the neighborhood of the ordinary room temperature. When a fire, etc., is generated and the room temperature arrives at 40 deg.C, the output of the range decision part 13 goes to a high level, and it follows that only the fixed resistor 8 is connected in series to the thermistor 7, then, the linear temperature-output potential characteristic can be obtained in the neighborhood of a high temperature. in such a way, it is possible to obtain a linear characteristic in a detecting temperature range of wide range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J] The present invention relates to a temperature detector that senses an increase in the temperature of the environment using a nonlinear heat-sensitive resistor such as a thermistor.

BACKGROUND ART Many temperature detectors have been proposed that detect the occurrence of a fire by using a heat-sensitive resistor to detect a temperature rise caused by a fire. In recent years, it has been proposed to use the same detector for multiple applications, and in that case, the problem that must be solved is that different information is required for each application, so it is difficult to use the same detector for multiple applications. It's a matter of how much information you send in.

For example, Japanese Unexamined Patent Publication No. 59-91501 discloses a temperature detector having a circuit configuration as shown in FIG. 3 and capable of obtaining detected temperature-output signal characteristics as shown in FIG. 4. That is, when both switches 32 and 33 are closed by a control signal from the control circuit 31, the reference voltage is lowered, and the amplification gain of the operational amplifier is increased, the detected temperature signal obtained from the platinum resistance temperature detector 35 follows a characteristic straight line. It is converted into an output voltage according to the output characteristic indicated by C.

This means that an output voltage with sufficient resolution can be obtained in a narrow temperature range of 10 to 30°C, and it can be used as a detector for air conditioning equipment. In addition, both switches 32 and 33 are opened by a control signal from the control circuit 31,
When the reference voltage is increased and the amplification gain of the operational amplifier 34 is decreased, the detected temperature signal is converted into an output voltage according to the output characteristic indicated by the characteristic line. This is 4
Output voltage can be obtained in a wide temperature range of 0 to 90°C, and it can be used as a detector for fire alarm equipment.

According to the above conventional example, whether this detector is used for air conditioning equipment or fire alarm equipment, the signal output from the operational amplifier can be digitized and transmitted by the same analog converter 36. be. That is, on the receiver side that receives and receives this digitized signal, by referring to the state of the control circuit 31, the detected temperature represented by the signal can be determined even if the signal is the same digital signal. be.

[Problems to be Solved by the Invention] However, the above conventional example is a detector that uses an expensive element such as a platinum side temperature resistor as a temperature detection element, and it is not possible to use an inexpensive element such as a thermistor. This is not possible, because the platinum resistance thermometer is a linear heating resistor at least in the above detection temperature range, and if a nonlinear thermistor or the like is used, the processing of the signal obtained with this circuit configuration will be complicated. It is.

In addition, in the conventional example described above, the control circuit 31 is managed on the receiving side, and in equipment where a large number of detectors must be managed at once, the burden on the receiving side becomes large and the entire equipment is signal processing ability is reduced.

[Means for Solving the Problems] In the temperature detector according to the present invention, a series circuit consisting of a nonlinear heat-sensitive resistor such as a thermistor and a fixed resistor is connected to a power source,
A temperature sensor that obtains a temperature detection signal from a potential change at a series connection point in a series circuit is provided with a changing means for changing and setting the resistance value of a fixed resistor, and a comparison means for comparing the potential at the series connection point with a predetermined value. The above problem has been solved by including a control means for controlling the changing means using the output of the comparing means, and further transmitting the output of the control means to the outside together with the temperature detection signal.

[Operation] The load temperature characteristics of the thermistor are shown in FIG. That is, if a thermistor and a fixed resistor serving as a load are connected in series, and the potential at the series connection point is taken as the temperature is varied, the graph in FIG. 2 will be obtained. Here, each curve shows the state of change when the resistance value R of the fixed resistor serving as the load is changed. As is clear from this graph, the portion where the relationship between temperature and output potential is a straight line can be changed by the value of the load resistance.The present invention focuses on this point, and the relationship is By changing the load resistance value so that it is a straight line, and changing the reference value if necessary, it is possible to obtain linear characteristics even in a non-linear heat-sensitive resistor such as a thermistor.

[Example 1] FIG. 1 is a diagram showing the main part of an embodiment of a temperature detector according to the present invention, and this temperature detector 1 responds to address polling from a receiver (not shown). , for transmitting temperature detection signals for air conditioning equipment or fire alarm equipment. That is, address signals sequentially sent from the receiver side are input to the address detection circuit 3 via the transmission circuit 2. The address detection circuit 3 compares the address with the unique address of this detector 1 set in the address setter 4, and sends a drive signal to the command identification circuit 5 only when the address matches. The command identification circuit 5 activated by this drive signal identifies the content of the command signal sent successively after the address signal and generates a command signal according to the content. Assume that a command signal to collect a temperature detection signal is generated. Upon receiving this signal, a switching transistor 6, which controls power supply to each component to be described later, is turned on. The main purpose of controlling the power supply to each component is to reduce the power consumption of the entire detector.
It is not directly related to the present invention.

Now, when power is supplied, the temperature detecting section 10 formed by the thermistor 7 and two fixed resistors 8.9 connected in series functions, and a potential corresponding to the detected temperature is generated at the series connection point 11. The potential signal corresponding to this detected temperature is generated by the temperature signal amplifying section 1.
2 and the temperature range determining section 13. The temperature signal amplifying section 12 includes an operational amplifier 14, which amplifies the potential signal at a predetermined rate, and its output is input to an analog input terminal of an analog-to-digital converter 15. The temperature range determining unit 13 determines whether the potential signal from the temperature detecting unit 10 exceeds a predetermined range, and is configured to determine whether the potential signal from the temperature detecting unit 10 exceeds a predetermined range, and determines whether or not the potential signal from the temperature detecting unit 10 exceeds a predetermined range. It consists of a comparator 18 that compares and outputs input potentials. In this embodiment, the output is set to be high level when the input potential from the temperature detection section 10 exhibits a potential corresponding to a temperature of approximately 40° C. or higher.

The output of the temperature range determining section 13 is supplied to the sampling section 19. This one sampling section is provided in order to adopt only the output of the temperature range determining section 13 at the initial stage of the temperature detection operation as a determination result, and to prevent the range changing means described later from chattering. A time constant circuit consisting of a capacitor 20 and a resistor 21, and N
It is composed of an AND circuit 22.

The output of the sampling section 19 is sent to the sample hold section 23.
is supplied to the range changing means via.

This sample hold section 23 mainly includes a time constant circuit consisting of a capacitor 24 and a resistor 25, and two inverters 26.
27, and holds the determination result obtained from the sampling section 19 until the series of operations for temperature detection is completed.

The range changing means includes a first transistor 28 whose collector-emitter circuit is connected in parallel with the fixed resistor 9 of the temperature detecting section 10, and a fixed resistor for adjusting the output voltage of the temperature signal amplifying section 12. Collector in parallel with 29
The base of the first transistor 28 is connected to the collector side of the second transistor 30, and the base of the second transistor 30 is connected to the sample hold section 2.
It is connected to the output side of 3.

The above is the configuration of one embodiment of the temperature detector according to the present invention.The sampling section 19. Of course, the sample hold section 23 and the like can be replaced with existing equivalent circuits.

Now, the operation of the temperature detector 1 is as follows.

In other words, if the room temperature is normal, the temperature range determination unit 1
The output of No. 3 exhibits a low level, and is supplied to the base of the second transistor 30 of the range changing means via the sampling section 19 and sample hold section 23. As a result, the second transistor 30 is turned on, so the first transistor 28 is turned off. Then, the fixed resistor 9 connected in parallel with the first transistor 28 becomes effective, so the two fixed resistors 8.9 are connected in series with the resistor 7, and the load temperature characteristics are as follows. As is clear from the 0 curve A shown in FIG. 2, in this state, a linear temperature-output potential characteristic is usually obtained near the room temperature. This output potential is input to the temperature signal amplification section 12 and amplified at a predetermined rate, and then converted into a digital signal by the analog-to-digital converter 15 and sent to the receiver side via the transmission circuit 2. At this time, the low level output from the temperature range determining section 13, which sets the range changing means to the low range of the normal temperature range, is also sent to the receiver side together with the digital signal via the transmission circuit 2. By referring to the output status of this temperature range determining section, the true detected temperature can be determined from the currently sent digital signal.

Next, when a fire or the like occurs and the indoor temperature reaches 40°C, the output of the temperature range determining section 13 becomes high level, and the output is passed through the sampling section 19 and the sample hold section 23 to the range changing means. 2 transistor 3
0 base. As a result, the second transistor 30 is turned off, and the first transistor 28 is turned on. Then, both ends of the fixed resistor 9 connected in parallel with the first transistor 28 are short-circuited and become invalid, so only one fixed resistor 8 is connected in series with the thermistor 7, and its load temperature characteristics As is clear from the 0 curve B shown in FIG. 2, in this state, a linear temperature-output potential characteristic is obtained near a temperature higher than the normal room temperature. This output potential is input to the temperature signal amplification section 12 and amplified at a predetermined rate, and then converted into a digital signal by the analog-to-digital converter 15 and sent to the receiver side via the transmission circuit 2. A high-level output from the temperature range determining section 13 that sets the range changing means to a high range within the abnormal temperature range is also sent to the receiver side together with the digital signal via the transmission circuit 2, and the receiver side receives the temperature By referring to the output status of the range determining section, the true detected temperature is determined from the currently sent digital signal.

[Effects of the Invention] As described above, in the temperature sensor according to the present invention, a series circuit consisting of a nonlinear heat-sensitive resistor such as a thermistor and a fixed resistor is connected to a power source, and temperature is detected from the potential change at the series connection point of the series circuit. In the temperature sensor that obtains the signal, a changing means is provided to change and set the resistance value of the fixed resistor, so linear characteristics can be obtained over a wide detection temperature range, and inexpensive elements such as thermistors can be used. can. Furthermore, since a comparison means for comparing the potential of the series connection point with a predetermined value and a control means for controlling the above-mentioned changing means based on the output of the comparison means are provided, the temperature range control can be managed by the detector itself. , it is possible to manage a large number of detectors at once without placing a large burden on the receiving side. Furthermore, since the output of the control means is transmitted to the outside together with the temperature detection signal, the receiving side can easily determine the true detected temperature by referring to the output of the control means.

Furthermore, by setting the output reversal temperature of the temperature range determination section to a temperature such as 60°C, the output of the control means can be directly used as a control signal for the smoke prevention equipment, as shown by terminal P in Fig. 1. It is also possible to do so.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of essential parts of an embodiment of a temperature detector according to the present invention, Fig. 2 is a characteristic curve diagram of a thermistor used in the detector of Fig. 1, and Fig. 3 is a block diagram of a conventional temperature detector. , FIG. 4 is a characteristic curve diagram of the detector of FIG. 3. 7... Thermistor, 8.9... Fixed resistance, 9.28
...Resistor and transistor constituting the changing means, 13.
・Temperature range determination unit as comparison means, 19.23・
...Sampling section and sample hold section as control means, 2...Transmission circuit

Claims (3)

[Claims] (1) In a temperature detector in which a series circuit consisting of a nonlinear heat-sensitive resistor such as a thermistor and a fixed resistor is connected to a power source and a temperature detection signal is obtained from a potential change at a series connection point of the series circuit, the resistance of the fixed resistor is A temperature detector characterized by having a changing means for changing and setting a value. (2) In a temperature detector in which a series circuit consisting of a nonlinear heat-sensitive resistor such as a thermistor and a fixed resistor is connected to a power source, and a temperature detection signal is obtained from a potential change at a series connection point of the series circuit, the resistance of the fixed resistor is A temperature sensor comprising a changing means for changing and setting a value, a comparing means for comparing the potential of the series connection point with a predetermined value, and a control means for controlling the changing means by the output of the comparing means. . (3) In a temperature detector in which a series circuit consisting of a nonlinear heat-sensitive resistor such as a thermistor and a fixed resistor is connected to a power source, and a temperature detection signal is obtained from a potential change at a series connection point of the series circuit, the resistance of the fixed resistor is It has a changing means for changing and setting a value, a comparing means for comparing the potential of the series connection point with a predetermined value, and a control means for controlling the changing means by the output of the comparing means, and the output of the controlling means is A temperature detector characterized in that the temperature detection signal is transmitted to the outside together with the temperature detection signal.