JPH07104735B2 - Temperature detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a temperature detector for detecting an increase in temperature of an environment with a non-linear thermosensitive resistor such as a thermistor.

[Prior Art] Many temperature detectors have been proposed, which detect a temperature rise due to a fire with a thermosensitive resistor and sense the occurrence of a fire. In recent years, it has also been proposed to use the same detector for multiple purposes, and the problem that must be solved in that case is that since different information is required for each purpose, in the same transmission capacity as the conventional one, It is how much information is sent.

For example, Japanese Patent Application Laid-Open No. 59-91501 discloses a temperature detector capable of obtaining a detected temperature-output signal characteristic as shown in FIG. 4 as a circuit configuration as shown in FIG. That is, when both switches 32 and 33 are closed by the control signal from the control circuit 31, the reference voltage is lowered, and the amplification gain of the operational amplifier 34 is increased, the detected temperature signal obtained from the platinum temperature measuring low antibody 35 has a characteristic straight line. It is converted into an output voltage according to the output characteristic shown 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. Further, when both the switches 32 and 33 are opened by the control signal from the control circuit 31, the reference voltage is raised and the amplification gain of the operational amplifier 34 is reduced, the detected temperature signal is output according to the output characteristic indicated by the characteristic line D. Converted to voltage. This means that an output voltage can be obtained in a wide temperature range of 40 to 90 ° C, and it can be used as a detector for fire alarm equipment.

According to the above conventional example, even if 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. is there. That is,
On the receiver side that receives the digitized signal, the detected temperature represented by the signal can be determined by referring to the state of the control circuit 31, even if the signal is the same digital signal.

[Problems to be Solved by the Invention] However, the above-mentioned conventional example is a detector using an expensive element such as a platinum resistance temperature detector as a temperature detecting element, and an element such as an inexpensive thermistor may be used. Can not. This is because the platinum side temperature resistor is a linear thermosensitive resistor at least in the above detection temperature range, and if a non-linear thermistor or the like is used, the processing of signals obtained by this circuit configuration becomes complicated.

Further, in the above conventional example, the control circuit 31 is managed on the receiving side, and in a facility where a large number of detectors must be managed collectively, the burden on the receiving side becomes large, and the entire facility Signal processing capability is reduced.

[Means for Solving the Problems] In the temperature detector according to the present invention, a series circuit composed of a non-linear thermosensitive resistor such as a thermistor and a fixed resistor is connected to a power source,
In a temperature detector that obtains a temperature detection signal from a potential change at a series connection point of the series circuit, changing means for changing and setting the resistance value of the fixed resistor, and comparison means for comparing the potential at the series connection point with a predetermined value. The control means for controlling the changing means by the output of the comparing means, and the output of the control means is transmitted to the outside together with the temperature detection signal, thereby solving the above problems.

[Operation] The load temperature characteristic of the thermistor is shown in FIG. That is, when the thermistor and a fixed resistor as a load are connected in series and the potential at the series connection point when the temperature is changed is taken, it becomes as shown in the graph of FIG. Where each curve is
It shows a state of change when the resistance value R of the fixed resistor serving as a load is changed. As is clear from this graph, the portion where the relationship between the temperature and the output potential is a straight line can be changed by the value of the load resistance value. Focusing on this point in the present invention,
In the target temperature range, the load resistance value is changed so that the relationship is in series, and if necessary, the reference value is also changed so that the linear characteristic can be obtained even in the non-linear heat sensitive resistor such as the thermistor. ing. Moreover, this change is also transmitted to the outside together with the temperature detection signal.

[Embodiment] FIG. 1 is a block diagram of a main part of an embodiment of a temperature detector according to the present invention. The temperature detector 1 responds to address polling from a receiver (not shown) side. The temperature detection signal for air conditioning equipment or fire alarm equipment is transmitted. That is, the 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 unique to the detector 1 set in the address setting device 4 with each other, and only when they match, the command identification circuit 5
Drive signal to. The command identification circuit 5 operated by this drive signal identifies the content of the command signal sent subsequently to the address signal, and generates a command signal according to the content. A command signal for collecting the temperature detection signal, which is the problem, is to be generated. In response to this signal, the switching transistor 6 that controls the power supply to each component described later is turned on. The main purpose of controlling the power supply to each component here is to reduce the power consumption of the entire detector, and is not directly related to the present invention.

Now, when power is supplied, the temperature detection unit 10 including the thermistor 7 and two fixed resistors 8 and 9 connected in series functions, and a potential corresponding to the detected temperature is generated at the series connection point 11. The potential signal according to the detected temperature is supplied to the temperature signal amplification unit 12 and the temperature range determination unit 13. Temperature signal amplifier
An operational amplifier 14 amplifies the potential signal at a predetermined ratio, and its output is input to the analog input terminal of the analog / digital converter 15. The temperature range determination unit 13 is for determining whether or not the potential signal from the temperature detection unit 10 exceeds a predetermined range, and determines the potential of the series connection point of the series circuit including the two fixed resistors 16 and 17. It comprises a comparator 18 for comparing and outputting input potentials. In this embodiment, the output is set to a high level when the input potential from the temperature detector 10 exhibits a potential corresponding to a temperature of about 40 ° C. or higher.

The output of the temperature range determination unit 13 is supplied to the sampling unit 19. The sampling unit 19 employs only the output of the temperature range determination unit 13 in the initial stage of the temperature detection operation as a determination result, and is provided to prevent the range changing unit described later from chattering, A time constant circuit including a capacitor 20 and a resistor 21, and a NAND circuit 22.

The output of the sampling section 19 is supplied to the range changing means via the sample hold section 23. The sample-hold section 23 is mainly composed of a time constant circuit consisting of a capacitor 24 and a resistor 25, and two inverters 26 and 27. The judgment result obtained from the sampling section 19 is used for the series of temperature detection operations. It is held until it is completed.

The range changing means is a fixed resistor for adjusting the output voltage of the temperature signal amplifying unit 12, as well as the first transistor 28 having a collector-emitter circuit connected in parallel with the fixed resistor 9 of the temperature detecting unit 10. 29 and a second transistor 30 having a collector-emitter circuit connected in parallel. The base of the first transistor 28 is connected to the collector side of the second transistor 30 and the second transistor 30 is connected.
The base of is connected to the output side of the sample hold unit 23.

The above is the configuration of one embodiment of the temperature detector according to the present invention.
Of course, 3 etc. can be replaced by an existing equivalent circuit.

The operation of the temperature detector 1 is as follows.

That is, if the room temperature is normal, the temperature range determination unit 13
Output is low level and its output is
It is supplied to the base of the second transistor 30 of the range changing means via 19 and the sample hold unit 23. As a result, the second transistor 30 is turned on, so that the first transistor 28 is turned off. Then the first transistor 2
Since the fixed resistor 9 connected in parallel with 8 becomes effective, the two fixed resistors 8 and 9 are connected in series with the thermistor 7, and the load temperature characteristic is as shown by the curve A in FIG. become. As is clear from the curve A, in this state, a linear temperature-output potential characteristic is usually obtained around the room temperature. This output potential is the temperature signal amplifier 12
To the receiver side via the transmission circuit 2 after being input to the receiver, amplified at a predetermined ratio, converted into a digital signal in the analog / digital converter 15. At this time, the low-level output from the temperature range determination unit 13 that sets the range changing unit 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, so that the receiver side Then, the true detected temperature can be determined from the digital signal currently sent by referring to the output status of the temperature range determination unit.

Next, when a fire etc. occurs and the room temperature reaches 40 ° C,
The output of the temperature range determination unit 13 exhibits a high level, and its output is supplied to the base of the second transistor 30 of the range changing means via the sampling unit 19 and the sample hold unit 23. This turns off the second transistor 30.
Therefore, 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 invalidated, so that only one fixed resistor 8 is connected in series with the thermistor 7,
The load temperature characteristic is as shown by the curve B in FIG. As is clear from the curve B, in this state, a linear temperature-output potential characteristic is obtained near the temperature higher than the normal room temperature. This output potential is input to the temperature signal amplifying section 12, amplified at a predetermined ratio, converted into a digital signal in the analog / digital converter 15, and sent to the receiver side via the transmission circuit 2. The high-level output from the temperature range determination unit 13 that sets the range changing means to the high range of the abnormal temperature range is also sent to the receiver side together with the digital signal via the transmission circuit 2, and the temperature is judged at the receiver side. By referring to the output status of the range determination unit, the true detected temperature is determined from the digital signal currently sent.

[Effects of the Invention] As described above, in the temperature detector according to the present invention, a series circuit including a non-linear thermosensitive resistor such as a thermistor and a fixed resistor is connected to a power source, and temperature detection is performed by a potential change at a series connection point of the series circuit. In the temperature detector for obtaining the signal, since the changing means for changing and setting the resistance value of the fixed resistance is provided, it is possible to obtain linear characteristics in a wide detection temperature range, and it is possible to use an element such as an inexpensive thermistor. it can. Further, since the comparison means for comparing the potential at the series connection point with the predetermined value and the control means for controlling the changing means by the output of the comparison means are provided, the detector itself can manage the temperature range control. A large number of detectors can be collectively managed without imposing a heavy burden on the receiving side. Further, 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.

By setting a temperature such as the output reversal temperature of the temperature range determination unit of 60 ° C., the output of the control means is directly used as a control signal of the smoke-proof and smoke-proof equipment, as indicated by the terminal P in FIG. It is also possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a main part 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 configuration diagram of a conventional temperature detector. , FIG. 4 is a characteristic curve diagram of the detector of FIG. 7 ... Thermistor, 8, 9 ... Fixed resistance, 9, 28 ... Resistor and transistor constituting change means, 13 ... Temperature range determination section as comparison means, 19, 23 ... Sampling section as control means And sample and hold unit, 2 ... Transmission circuit

Claims (1)

[Claims] 1. A temperature detector in which a series circuit including a non-linear thermosensitive low antibody such as a thermistor and a fixed resistance 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. Of the control means for controlling the changing means by the output of the comparing means. A temperature detector characterized in that the output is transmitted to the outside together with the temperature detection signal.