CN219714570U

CN219714570U - Temperature measuring circuit

Info

Publication number: CN219714570U
Application number: CN202320596787.7U
Authority: CN
Inventors: 杨小兵; 郝韩斌
Original assignee: Shenzhen Meimeimeichuangyi Medical Technology Co ltd
Current assignee: Shenzhen Meimeimeichuangyi Medical Technology Co ltd
Priority date: 2023-03-24
Filing date: 2023-03-24
Publication date: 2023-09-19
Anticipated expiration: 2033-03-24

Abstract

The utility model relates to the technical field of circuits, in particular to a temperature measuring circuit, which comprises: the electronic device comprises a reference resistor, a thermistor, a first electronic switch, an operational amplifier and a control module; the reference resistor and the thermistor are connected in series between a power supply and a ground wire to form a main circuit, and parallel points are arranged at two ends of the reference resistor and two ends of the thermistor on the main circuit; the operational amplifier and the control module are sequentially connected in series to form a parallel branch, and one end, close to the operational amplifier, of the parallel branch is connected with a parallel point through a first electronic switch; the first electronic switch is electrically connected with the control module; the control module switches the parallel connection position of the parallel branch circuit on the main circuit by using the first electronic switch so as to detect the first pressure difference at two ends of the reference resistor and the second pressure difference at two ends of the thermistor, and performs temperature measurement according to the ratio between the first pressure difference and the second pressure difference. Compared with the prior art, the temperature measuring circuit provided by the utility model has better measuring precision.

Description

Temperature measuring circuit

Technical Field

The utility model relates to the technical field of circuits, in particular to a temperature measuring circuit.

Background

Temperature is an important environmental parameter that is measured for temperature control in many manufacturing processes and in the workplace and life. The temperature measurement by using a thermistor is a common temperature measurement method. A thermistor is a sensor resistor whose resistance value changes with a change in temperature. The positive temperature coefficient thermistor (positive temperature coefficient thermistor, PTC) and the negative temperature coefficient thermistor (negative temperature coefficient thermistor, NTC) are classified according to temperature coefficients. The resistance value of the PTC increases with an increase in temperature, and the resistance value of the NTC decreases with an increase in temperature.

Both NTC and PTC can be applied to temperature measurement and the principle of temperature measurement is similar, but NTC temperature measurement schemes are currently generally used in view of cost factors. Taking an NTC temperature measurement technique as an example, the existing NTC temperature measurement technique is based on the principle of resistive voltage division of a reference voltage. The basic idea is to give a voltage reference source, let the current of the voltage reference source flow through the series connection of the NTC and another reference resistor to ground, the upper and lower positions of the NTC and the reference resistor are not limited (typically, the NTC is located at the ground), and a path of analog-digital converter (analog to digital converter, ADC) is led out from the voltage division point of the voltage reference source by the NTC and the reference resistor to sample the voltage, and the ADC voltage sampling value is compared with a "standard voltage division value-temperature value" stored in the microcontroller in advance, so as to obtain the temperature value. According to the temperature measurement method, one path of ADC is directly led out from the NTC and the reference resistor to the voltage division point of the voltage reference source for voltage sampling, and is influenced by the precision of the voltage reference source, such as voltage change of the voltage reference source, even if the ambient temperature value is unchanged, the measured ADC voltage sampling value is changed, and under the condition, the temperature measurement precision is greatly influenced.

Disclosure of Invention

In order to solve the technical problem that the temperature measurement precision is not accurate enough due to the precision of a voltage reference source when the temperature measurement is performed by adopting a resistor voltage division principle at present, the utility model provides a temperature measurement circuit which measures the temperature according to the ratio between a first differential pressure at two ends of a reference resistor and a second differential pressure at two ends of the thermistor. Because the ratio is not influenced by the change of the power supply voltage, compared with the prior art, the temperature measuring circuit provided by the utility model has better measuring precision.

In order to solve the above technical problems, the present utility model provides a temperature measurement circuit, including:

the electronic device comprises a reference resistor, a thermistor, a first electronic switch, an operational amplifier and a control module;

the reference resistor and the thermistor are connected in series between a power supply and a ground wire to form a main circuit, and parallel points are arranged at two ends of the reference resistor and two ends of the thermistor on the main circuit;

the operational amplifier and the control module are sequentially connected in series to form a parallel branch, and one end, close to the operational amplifier, of the parallel branch is connected with the parallel point through the first electronic switch;

the first electronic switch is electrically connected with the control module;

the control module switches the parallel connection position of the parallel branch on the main circuit by using the first electronic switch so as to detect a first differential pressure at two ends of the reference resistor and a second differential pressure at two ends of the thermistor, and performs temperature measurement according to the ratio between the first differential pressure and the second differential pressure.

In one possible implementation, the number of thermistors is multiple and serially connected in turn to the main circuit for measuring the ambient temperature at different locations.

In one possible implementation, a short-circuit branch is provided on the main circuit at all or part of the thermistor, and a second electronic switch is provided on the short-circuit branch, and when the second electronic switch is closed, the short-circuit is performed on the thermistor between the actual parallel positions of the short-circuit branch on the main circuit.

In one possible implementation, the second electronic switch is electrically connected to and controlled by the control module.

In one possible implementation, the temperature measurement circuit further includes a first voltage regulator resistor connected in series between the power supply and the reference resistor on the main circuit, and a second voltage regulator resistor connected in series between the thermistor and the ground.

In one possible implementation, the temperature measurement circuit further includes a communication module electrically connected to the control module.

In one possible implementation, the thermistor is a negative temperature coefficient thermistor NTC or a positive temperature coefficient thermistor PTC.

In one possible implementation, the power supply is a regulated power supply or a constant current power supply.

In one possible implementation, the control module includes an analog-to-digital converter and a microcontroller.

In one possible implementation, the temperature measurement circuit further includes a display module electrically connected to the control module.

Compared with the prior art, the temperature measuring circuit provided by the embodiment of the utility model has the following advantages:

the temperature measuring circuit provided by the utility model comprises a reference resistor, a thermistor, a first electronic switch, an operational amplifier and a control module. The reference resistor is a constant value resistor, can be connected in series with the thermistor between a power supply and a ground wire to form a main circuit, and parallel points are arranged at two ends of the reference resistor and two ends of the thermistor on the main circuit. The operational amplifier can perform operational amplification processing on signals and form a parallel branch after being connected with the control module in series in sequence, one end, close to the operational amplifier, of the parallel branch is connected with the parallel point through the first electronic switch, and the other end of the parallel branch can adopt grounding processing. The control module can control the parallel connection position of the parallel branch circuit on the main circuit by using the first electronic switch to detect the first pressure difference at two ends of the reference resistor and the second pressure difference at two ends of the thermistor, and perform temperature measurement according to the ratio between the first pressure difference and the second pressure difference.

The temperature measurement circuit provided by the utility model has better measurement precision compared with the prior art because the temperature measurement is carried out according to the ratio between the first differential pressure and the second differential pressure, and the ratio is not influenced by the change of the power supply voltage.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments or the conventional techniques of the present utility model, the drawings required for the descriptions of the embodiments or the conventional techniques will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present utility model, and other drawings may be obtained according to the drawings without inventive effort for those skilled in the art.

FIG. 1 is a schematic diagram of an embodiment of a temperature measurement circuit provided by the present utility model;

FIG. 2 is a schematic diagram of another embodiment of a temperature measurement circuit provided by the present utility model;

FIG. 3 is a schematic diagram of another embodiment of a temperature measurement circuit provided by the present utility model;

FIG. 4 is a schematic diagram of another embodiment of a temperature measurement circuit according to the present utility model.

Description of the embodiments

In order that the utility model may be readily understood, a more complete description of the utility model will be rendered by reference to the appended drawings. Embodiments of the utility model are illustrated in the accompanying drawings. This utility model may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this utility model belongs. The terminology used herein in the description of the utility model is for the purpose of describing particular embodiments only and is not intended to be limiting of the utility model.

It will be understood that the terms first, second, etc. as used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another element. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," and/or the like, specify the presence of stated features, integers, steps, operations, elements, components, or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof.

It will be understood that when an element is referred to as being "fixed to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only.

In the present utility model, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate an azimuth or a positional relationship based on that shown in the drawings. These terms are only used to better describe the present utility model and its embodiments and are not intended to limit the scope of the indicated devices, elements or components to the particular orientations or to configure and operate in the particular orientations. Also, some of the terms described above may be used to indicate other meanings in addition to orientation or positional relationships, for example, the term "upper" may also be used to indicate some sort of attachment or connection in some cases. The specific meaning of these terms in the present utility model will be understood by those of ordinary skill in the art according to the specific circumstances.

Furthermore, the terms "mounted," "configured," "provided," "connected," and "connected" are to be construed broadly. For example, it may be a fixed connection, a removable connection, or a unitary construction; may be a mechanical connection, or an electrical connection; may be directly connected, or indirectly connected through intervening media, or may be in internal communication between two devices, elements, or components. The specific meaning of the above terms in the present utility model can be understood by those of ordinary skill in the art according to the specific circumstances.

To solve the above technical problems, the present utility model provides a temperature measuring circuit, referring to fig. 1-4, which includes:

the electronic device comprises a reference resistor, a thermistor, a first electronic switch, an operational amplifier and a control module. The reference resistor and the thermistor are connected in series between a power supply and a ground wire to form a main circuit, and parallel points are arranged at two ends of the reference resistor and two ends of the thermistor on the main circuit. The operational amplifier and the control module are sequentially connected in series to form a parallel branch, and one end, close to the operational amplifier, of the parallel branch is connected with the parallel point through the first electronic switch; the first electronic switch is electrically connected with the control module; the control module switches the parallel connection position of the parallel branch on the main circuit by using the first electronic switch so as to detect a first differential pressure at two ends of the reference resistor and a second differential pressure at two ends of the thermistor, and performs temperature measurement according to the ratio between the first differential pressure and the second differential pressure.

Specifically, the temperature measuring circuit of the present utility model will be described in detail with reference to fig. 1.

As in fig. 1, vcc is represented as a power supply, R2 is represented as a reference resistor, R3 (labeled NTC) is represented as a thermistor, and the circuit of R2-R3-ground is represented as a main circuit. S1, S2 and S3 are denoted as first electronic switches, AMP, i.e. AMPlifier, an operational AMPlifier, and an adc+ micro control unit (microcontroller unit, MCU) a control module. The circuit of the first electronic switch-operational amplifier-control module is a parallel branch. It should be noted that the specific components referred to in fig. 1 are only exemplary, and are not meant to limit the present utility model.

As shown in fig. 1, parallel points are disposed at two ends of the reference resistor and two ends of the thermistor on the main circuit, and one end of the parallel branch close to the operational amplifier is connected to the parallel point through the first electronic switch, and the other end is grounded (not shown in the figure). The parallel branch can thus be switched in parallel position in the main circuit by closing different first electronic switches. And after the first electronic switch is closed, the operational amplifier can amplify the voltage value of the parallel position on the main circuit and then transmit the amplified voltage value to the control module, and the control module can measure and record the voltage value of the parallel position on the main circuit. The first electronic switch is electrically connected with the control module, the first electronic switch can be an electronic change-over switch, the control module can conduct time-sharing gating on the first electronic switch, and through multiple times of switching of parallel positions and measurement of voltage, the first pressure difference at two ends of the reference resistor and the second pressure difference at two ends of the thermistor can be finally measured.

The operational amplifier adopted by the parallel branch circuit can amplify the potential difference measured between the parallel position of the main circuit and the ground wire and send the amplified potential difference to the control module. Since the input bias current of the operational amplifier affects the measurement accuracy, in the utility model, in order to reduce the influence factor, the operational amplifier adopts a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) or Junction Field-Effect Transistor (JFET) structure, and the current passing through the parallel branch circuit can be ignored according to the structural characteristics, namely, the current passing through the reference resistor and the thermistor on the main circuit can be considered to be always the same even if the parallel position of the parallel branch circuit is switched in the temperature measurement process. At this time, the ratio of the first differential pressure to the second differential pressure is equal to the ratio between the resistance of the reference resistor and the resistance of the thermistor. Therefore, after determining the ratio between the first differential pressure and the second differential pressure, the resistance of the current thermistor can be determined according to the ratio and the resistance of the reference resistor, and then the currently determined temperature value is inquired and determined according to the pre-stored mapping relation of the resistance and the temperature of the thermistor.

As described by way of example with reference to fig. 1, the temperature measurement steps are as follows:

step (1), only S1 is closed, and a point voltage value Va is measured;

step (2), only S2 is closed, and the voltage value Vb at the point b is measured;

step (3), only closing the S3, and measuring the voltage value Vc of the point c;

step (4), calculating the thermistor resistance value R3=R2× (Vb-Vc)/(Vb-Va);

and (5) inquiring and determining the temperature value corresponding to R3 as the current measured temperature value according to the pre-stored mapping relation of the resistance value and the temperature of the thermistor.

The temperature measuring circuit mainly measures the temperature according to the ratio between the first differential pressure and the second differential pressure, and the ratio is not influenced by the change of the power supply voltage, so that the temperature measuring circuit provided by the utility model has better measuring precision compared with the prior art.

Specifically, referring to fig. 2-4, the temperature measuring resistor can be arranged in some actual scenes, such as measuring the temperature of some large sites or different positions of large equipment, and the temperature measuring circuit can be expanded, such as linear expansion or array expansion. In the expansion process, a plurality of thermistors need to be connected in series in the main circuit, as compared with fig. 1, thermistors R5 and R6 are connected in series in the expansion process in fig. 2, as compared with fig. 2 and 3, and the array arrangement of three main circuits is expanded in the expansion process in fig. 4.

Specifically, referring to the above embodiment, when the power supply voltage is fixed, when the thermistor connected in series with the main circuit is too many, the current of the main circuit is too small, which may cause that the measured value of the voltage division of the parallel point is not in the optimal response interval of the operational amplifier, and the first voltage difference between the two ends of the measured reference resistor and the second voltage difference between the two ends of the thermistor to be measured are too small, so that the measurement accuracy is finally affected by the inaccuracy of the ratio, or the voltage value of the measured voltage division point is too low, and the lowest response voltage value lower than the operational amplifier cannot be measured, so that the expansion quantity of the thermistor is limited.

Therefore, in this embodiment, a short circuit branch may be disposed at all or part of the thermistor of the main circuit, a second electronic switch is disposed on the short circuit branch, and when the second electronic switch is turned on, the thermistor between the actual parallel positions of the short circuit branch on the main circuit may be subjected to short circuit treatment, so as to reduce the load of the main circuit, increase the current passing through the reference resistor and the thermistor to be measured, thereby improving the measurement accuracy, and making the number of expansion of the thermistor unlimited.

For example, referring to fig. 2, S6, S7 and S8 are second electronic switches, and if R3, R5 and R6 are present in the main circuit, the main circuit current is too small, which affects the measurement accuracy. At this time, if temperature measurement is required for the position of R5, that is, the resistance of R5 needs to be measured, in order to improve accuracy, in the measurement process, closing processing may be performed on S6 and S8, so that R3 and R6 are shorted, the current passing through the reference resistor R2 and the thermistor R5 in the main circuit is improved, the first differential pressure and the second differential pressure are increased, and the measurement accuracy is improved.

For example, referring to the above description, fig. 3 is another design, if the measurement at R6 is needed, in order to improve the accuracy, the short circuit between R3 and R5 can be achieved by closing S7, without closing S6, and the number of control times is reduced.

Specifically, the second electronic switch may be electrically connected to the control module, and in the case of having a plurality of thermistors, when performing temperature measurement, the control module may control the second electronic switch to be closed, so that other part or all of the thermistors except the to-be-measured thermistor are short-circuited, the current passing through the to-be-measured thermistor and the reference resistor is increased, and the measurement accuracy is improved.

Specifically, in order to avoid the voltage acquisition point on the main circuit from tending to the power supply rail (the power supply side and the ground side) and always being in the optimal linear interval of the input of the operational amplifier, the temperature measurement precision is improved. Illustratively, taking fig. 1 as an example, R1 represents a first voltage stabilizing resistor and R4 represents a second voltage stabilizing resistor.

Specifically, the temperature measurement circuit may further include a communication module, where the communication module may be a bluetooth module, a wireless network (wireless fidelity, WIFI) or other wireless and wired communication modules, and after the control module measures the temperature, the communication module may send temperature measurement data to other devices.

Specifically, the thermistor may be a negative temperature coefficient thermistor NTC or a positive temperature coefficient thermistor PTC, and fig. 1 to 4 illustrate NTC as an example, and the type of the thermistor is not particularly limited in this embodiment.

Specifically, in order to improve the measurement accuracy, the power supply may be a regulated power supply or a constant current power supply.

Specifically, the control module may include an analog-to-digital converter and a microcontroller, where the analog-to-digital converter is configured to perform analog-to-digital conversion on an analog signal collected by the operational amplifier, and send the analog signal to the microcontroller for storage and processing, and the microcontroller further calculates a ratio of the first differential pressure to the second differential pressure, and further determines the current measurement temperature according to the ratio.

Specifically, the measuring circuit further comprises a display module, a driving circuit of the display module is electrically connected with the control module, and the display module can be used for displaying temperature measurement data and is convenient to observe.

The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the utility model, which are described in detail and are not to be construed as limiting the scope of the utility model. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the utility model, which are all within the scope of the utility model. Accordingly, the scope of protection of the present utility model is to be determined by the appended claims.

Claims

1. A temperature measurement circuit, comprising:

the first electronic switch is electrically connected with the control module;

the control module switches the parallel connection position of the parallel branch circuit on the main circuit by using the first electronic switch so as to detect a first pressure difference at two ends of the reference resistor and a second pressure difference at two ends of the thermistor, and performs temperature measurement according to the ratio between the first pressure difference and the second pressure difference.

2. The thermometry circuit of claim 1, wherein the number of thermistors is plural and serially connected in turn on the main circuit for measuring the ambient temperature at different locations.

3. The temperature measurement circuit according to claim 2, wherein a short circuit branch is provided on the main circuit at all or part of the thermistor, a second electronic switch is provided on the short circuit branch, and when the second electronic switch is closed, the short circuit treatment is performed on the thermistor between the actual parallel positions of the short circuit branch on the main circuit.

4. The thermometry circuit of claim 3, wherein the second electronic switch is electrically connected to and controlled by the control module.

5. The thermometric circuit of any of claims 1 to 4, further comprising a first voltage stabilizing resistor and a second voltage stabilizing resistor, the first voltage stabilizing resistor being connected in series on the main circuit between the power supply and the reference resistor, the second voltage stabilizing resistor being connected in series between the thermistor and the ground.

6. The thermometry circuit of any one of claims 1 to 4, further comprising a communication module electrically connected to the control module.

7. The thermometric circuit of any of claims 1 to 4, wherein the thermistor is a negative temperature coefficient thermistor NTC or a positive temperature coefficient thermistor PTC.

8. The temperature measurement circuit of any one of claims 1 to 4, wherein the power supply is a regulated power supply or a constant current power supply.

9. The thermometric circuit of any of claims 1 to 4, wherein the control module comprises an analog to digital converter and a microcontroller.

10. The thermometry circuit of any one of claims 1 to 4, further comprising a display module electrically connected to the control module.