Multichannel PT temperature measuring device based on analog switch

Abstract

The utility model relates to the technical field of PT temperature measuring circuit devices, in particular to a multichannel PT temperature measuring device based on an analog switch, which comprises a constant current source circuit, a multichannel switch switching circuit and an MCU (Microprogrammed Control Unit) which are connected with one another, the multi-channel switch switching circuit comprises a second analog switch chip and a third analog switch chip which are connected with each other, and first pins on the second analog switch chip and the third analog switch chip are used for being connected with WPT0 signals. Second pins on the second analog switch chip and the third analog switch chip are used for being in signal connection with a WPT1; a third pin of the second analog switch chip is connected with the constant current source circuit, and a third pin of the third analog switch chip is connected with the MCU. A channel switching method is adopted to build a discrete scheme, so that the problems of more devices and resource occupation of a traditional scheme are solved, and the problems of high cost, difficulty in maintenance and the like of an integrated temperature measurement module are also solved.

Description

Technical Field

[0001] The utility model relates to the technical field of PT temperature measurement circuit devices, in particular to a multi-channel PT temperature measurement device based on an analog switch. Background Art

[0002] The traditional PT temperature measurement circuit, as Figure 1 shown, is composed of an operational amplifier, a triode, a thermal resistor, etc. The thermal resistor is connected in series into a constant current source circuit. At this time, a voltage difference will be generated across the thermal resistor. After the voltage across the thermal resistor is collected by an ADC chip, the corresponding temperature is calculated through an MCU.

[0003] However, when the number of channels increases, this circuit layout method will seriously occupy the space of the PCB board and consume the resources of the MCU pins, affecting the use of other functions. At the same time, the accuracy of temperature measurement is also easily affected by key devices such as the temperature drift of the triode and the accuracy of the resistor.

[0004] Now, compared with the discrete temperature measurement module, the integrated temperature measurement module has the following disadvantages:

[0005] 1. Limited customizability: The integrated temperature measurement module usually has fixed functions and interfaces, which may limit the user's ability to customize the system. In contrast, the discrete temperature measurement solution allows users to select and optimize each component according to specific needs.

[0006] 2. Price factor: The integrated temperature measurement module usually integrates multiple functions, so the price may be relatively high. The discrete temperature measurement solution can select individual components according to needs, which may be more cost-effective.

[0007] 3. Specific environment adaptability: The integrated temperature measurement module is usually designed for specific application scenarios, such as household appliances, automobiles, etc. If the application scenario requires a specific temperature measurement solution, it may be necessary to select and configure discrete components by oneself.

[0008] 4. Difficult maintenance and upgrade: If there is a problem with the integrated temperature measurement module or it needs to be upgraded, it may be necessary to replace the entire module. The discrete temperature measurement solution can more conveniently replace or upgrade a certain component separately.

[0009] Therefore, there is an urgent need for a new technical solution to solve the above technical problems. Content of the Utility Model

[0010] The purpose of the utility model is to overcome the problems of the above-mentioned existing technologies, and provides a multi-channel PT temperature measurement device based on an analog switch, so as to solve the technical problems of the complex traditional circuit structure, resource occupation, and the high cost and difficult maintenance of the integrated temperature measurement module compared with the discrete temperature measurement module.

[0011] The above object is achieved by the following technical solutions:

[0012] A multi-channel PT temperature measurement device based on analog switches, comprising a constant current source circuit, a multi-channel switch switching circuit and an MCU connected to each other; the multi-channel switch switching circuit includes a second analog switch chip and a third analog switch chip connected to each other. The first pins on the second analog switch chip and the third analog switch chip are used to connect to the WPT0 signal, and the second pins on the second analog switch chip and the third analog switch chip are used to connect to the WPT1 signal; the third pin of the second analog switch chip is connected to the constant current source circuit, and the third pin of the third analog switch chip is connected to the MCU.

[0013] Further, the second analog switch chip and the third analog switch chip have the same specifications, and the model numbers are both 75HC4051D.

[0014] Further, the ninth pin of the second analog switch chip and the eleventh pin of the third analog switch chip are connected to each other to form a CH2 channel; the tenth pin of the second analog switch chip and the tenth pin of the third analog switch chip are connected to each other to form a CH1 channel; the eleventh pin of the second analog switch chip and the ninth pin of the third analog switch chip are connected to each other to form a CH0 channel.

[0015] Further, a tenth resistor, an eleventh resistor and a twelfth resistor are respectively connected to the CH0 channel, the CH1 channel and the CH2 channel, and the other ends of the tenth resistor, the eleventh resistor and the twelfth resistor are respectively connected to the power supply.

[0016] Further, a first π filter circuit is connected to the first pin of the third analog switch chip, and a second π filter circuit is connected to the second pin of the third analog switch chip.

[0017] Further, the first π filter circuit includes a fifth resistor, a fourth capacitor and a sixth resistor connected to each other; the second π filter circuit includes a seventh resistor, a seventh capacitor and an eighth resistor connected to each other.

[0018] Further, the constant current source circuit includes a constant current source chip. The sixth pin of the constant current source chip is connected to the third pin, the seventh pin is connected to the second pin, and the second pin is connected to the third pin. A third diode is provided at the connection end of the second pin and the third pin. The cathode of the third diode is connected to the third pin of the second analog switch chip through the fifteenth resistor.

[0019] Further, a sixteenth resistor and a seventeenth resistor are connected in parallel to the anode of the third diode, and an eighteenth resistor and a nineteenth resistor are connected in parallel to the cathode of the third diode. The other ends of the sixteenth resistor, the seventeenth resistor, the eighteenth resistor, and the nineteenth resistor are respectively connected to the first pin of the constant current source chip.

[0020] Further, the model of the constant current source chip is LM334MX.

[0021] A multi-channel PT temperature measurement device based on an analog switch provided by the present invention uses a channel switching method to build a discrete solution, which not only solves the problems of many devices and resource occupation in the traditional solution, but also solves the problems of high cost and difficult maintenance of the integrated temperature measurement module. The constant current source discrete temperature measurement solution built by the multi-channel analog switch has the advantages of more flexible design, lower cost, and can save the PCB space to a certain extent. In addition, when collecting temperature, it will not be affected by the temperature drift of external transistors, thus resulting in the accuracy of temperature collection. Description of the Drawings

[0022] Figure 1 It is a traditional PT temperature measurement circuit diagram in the prior art;

[0023] Figure 2 The circuit diagram of a multi-channel PT temperature measurement device based on an analog switch of the present invention. Detailed Embodiments

[0024] The present invention will be further described in detail below with reference to the drawings and embodiments. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] As Figure 2 shown, a multi-channel PT temperature measurement device based on an analog switch includes a constant current source circuit, a multi-channel switch switching circuit, and an MCU that are connected to each other;

[0026] The multi-channel switch switching circuit includes a second analog switch chip U2 and a third analog switch chip U3 that are connected to each other. The first pin Y4 on the second analog switch chip U2 and the third analog switch chip U3 is used to connect to the WPT0 signal, and the second pin Y6 on the second analog switch chip U2 and the third analog switch chip U3 is used to connect to the WPT1 signal; the third pin Z of the second analog switch chip U2 is connected to the constant current source circuit, and the third pin Z of the third analog switch chip U3 is connected to the MCU.

[0027] Working principle:

[0028] A constant current is designed through the constant current source circuit, and the constant current is delivered to the second analog switch chip U2. The second analog switch chip U2 and the third analog switch chip U3 cooperate with each other to switch, so as to realize the acquisition of temperature, and output the voltage PT to the MCU. The circuit temperature is measured through this design method.

[0029] It should be noted that in this embodiment, the second analog switch chip U2 and the third analog switch chip U3 have the same specifications, and the model is 75HC4051D; the 74HC4051D chip has three digital selection inputs (S0 to S2) and an active LOW enable input (EN), and is also equipped with eight independent input / output ports (Y0 to Y7) and a common input / output port (Z).

[0030] The ninth pin S2 of the second analog switch chip U2 is connected to the eleventh pin S0 of the third analog switch chip U3 to form the CH2 channel;

[0031] The tenth pin S1 of the second analog switch chip U2 is connected to the tenth pin S1 of the third analog switch chip U3 to form the CH1 channel;

[0032] The eleventh pin S0 of the second analog switch chip U2 is connected to the ninth pin S2 of the third analog switch chip U3 to form the CH0 channel;

[0033] The CH0 channel, the CH1 channel and the CH2 channel are used for signal acquisition and transmission.

[0034] Specifically, a tenth resistor R10, an eleventh resistor R11 and a twelfth resistor R12 are respectively connected to the CH0 channel, the CH1 channel and the CH2 channel, and the other ends of the tenth resistor R10, the eleventh resistor R11 and the twelfth resistor R12 are respectively connected to the power supply VCC.

[0035] In this embodiment, the tenth resistor R10, the eleventh resistor R11 and the twelfth resistor R12 are used as pull-up resistors to give a high-level state to the signal in advance.

[0036] When an external signal is input, through the mutual cooperation of the second analog switch chip U2 and the third analog switch chip U3, the state of the high and low levels of the control signal can be controlled by controlling the sixth pin E# of the second analog switch chip U2 and the third analog switch chip U3, so as to control the conduction and medium of the signal.

[0037] By further coordinating the cooperation of the ninth pin S2, the tenth pin S1, and the eleventh pin S0 of the second analog switch chip U2 and the third analog switch chip U3, the acquisition of the CH0 channel, the CH1 channel, or the CH2 channel is controlled, and then the acquired signal is output to the MCU through the third pin ZPT of the third analog switch chip U3, and the required temperature measurement signal can be obtained.

[0038] As an optimization of this solution, a first π-filter circuit is connected to the first pin Y4 of the third analog switch chip U3, and a second π-filter circuit is connected to the second pin Y6 of the third analog switch chip U3.

[0039] Specifically, the first π-filter circuit includes a fifth resistor R5, a fourth capacitor C4, and a sixth resistor R6 connected to each other; the second π-filter circuit includes a seventh resistor R7, a seventh capacitor C7, and an eighth resistor R8 connected to each other.

[0040] In this embodiment, the WPT0 signal and the WPT1 signal can remove external interference through the first π-filter circuit and the second π-filter circuit, ensuring the stability of the circuit to a certain extent and enhancing the anti-interference ability.

[0041] In this embodiment, the constant current source circuit includes a constant current source chip U4. The sixth pin of the constant current source chip U4 is connected to the third pin, the seventh pin is connected to the second pin, the second pin is connected to the third pin, and a third diode D3 is provided at the connection end of the second pin and the third pin. The cathode of the third diode D3 is connected to the third pin Z of the second analog switch chip U2 through the fifteenth resistor R15.

[0042] The anode of the third diode D3 is connected in parallel with a sixteenth resistor R16 and a seventeenth resistor R17, and the cathode of the third diode D3 is connected in parallel with an eighteenth resistor R18 and a nineteenth resistor R19. The other ends of the sixteenth resistor R16, the seventeenth resistor R17, the eighteenth resistor R18, and the nineteenth resistor R19 are respectively connected to the first pin R of the constant current source chip U4.

[0043] Through the constant current source circuit in this embodiment, a stable and high-quality current signal can be output to the second analog switch chip U2; the sixteenth resistor R16, the seventeenth resistor R17, the eighteenth resistor R18, and the nineteenth resistor R19 in this circuit play a role in configuring the current, and the required current signal can be output by adjusting their resistance values.

[0044] The model of the constant current source chip U4 is LM334MX. The LM334MX chip is a current mode control integrated circuit produced by National Semiconductor Corporation of the United States and is used for power management applications.

[0045] The above is only to illustrate the embodiments of the present invention and is not intended to limit the present invention. For those skilled in the art, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A multi-channel PT temperature measuring device based on analog switches, characterized in that: It includes a constant current source circuit, a multi-channel switch circuit and an MCU connected to each other; The multi-channel switch switching circuit comprises a second analog switch chip (U2) and a third analog switch chip (U3) connected to each other, wherein the first pin (Y4) on the second analog switch chip (U2) and the third analog switch chip (U3) is used to connect to a WPT0 signal, and the second pin (Y6) on the second analog switch chip (U2) and the third analog switch chip (U3) is used to connect to a WPT1 signal; the third pin (Z) of the second analog switch chip (U2) is connected to the constant current source circuit, and the third pin (Z) of the third analog switch chip (U3) is connected to the MCU.

2. A multi-channel PT temperature measuring device based on analog switches according to claim 1, characterized in that: The second analog switch chip (U2) and the third analog switch chip (U3) have the same specifications, and both are model 75HC4051D.

3. A multi-channel PT temperature measuring device based on analog switches according to claim 1 or 2, characterized in that: The ninth pin (S2) of the second analog switch chip (U2) and the eleventh pin (S0) of the third analog switch chip (U3) are connected to each other to form a CH2 channel; The tenth pin (S1) of the second analog switch chip (U2) and the tenth pin (S1) of the third analog switch chip (U3) are connected to each other to form a CH1 channel; The eleventh pin (S0) of the second analog switch chip (U2) and the ninth pin (S2) of the third analog switch chip (U3) are connected to each other to form a CH0 channel.

4. A multi-channel PT temperature measuring device based on analog switches according to claim 3, characterized in that: The CH0 channel, the CH1 channel and the CH2 channel are respectively connected with a tenth resistor (R10), an eleventh resistor (R11) and a twelfth resistor (R12), and the other ends of the tenth resistor (R10), the eleventh resistor (R11) and the twelfth resistor (R12) are respectively connected to a power supply (VCC).

5. The multi-channel PT temperature measuring device based on analog switches according to claim 1 is characterized in that: A first π filter circuit is connected to the first pin (Y4) of the third analog switch chip (U3), and a second π filter circuit is connected to the second pin (Y6) of the third analog switch chip (U3).

6. A multi-channel PT temperature measuring device based on analog switches according to claim 5, characterized in that: The first π filter circuit includes a fifth resistor (R5), a fourth capacitor (C4) and a sixth resistor (R6) connected to each other; the second π filter circuit includes a seventh resistor (R7), a seventh capacitor (C7) and an eighth resistor (R8) connected to each other.

7. A multi-channel PT temperature measuring device based on analog switches according to claim 1, characterized in that: The constant current source circuit comprises a constant current source chip (U4), the sixth pin of the constant current source chip (U4) is connected to the third pin, the seventh pin is connected to the second pin, the second pin is connected to the third pin, and a third diode (D3) is provided at the connection end between the second pin and the third pin, and the cathode of the third diode (D3) is connected to the third pin (Z) of the second analog switch chip (U2) via a fifteenth resistor (R15).

8. The multi-channel PT temperature measuring device based on analog switches according to claim 7 is characterized in that: The anode of the third diode (D3) is connected in parallel with a sixteenth resistor (R16) and a seventeenth resistor (R17), the cathode of the third diode (D3) is connected in parallel with an eighteenth resistor (R18) and a nineteenth resistor (R19), and the other ends of the sixteenth resistor (R16), the seventeenth resistor (R17), the eighteenth resistor (R18) and the nineteenth resistor (R19) are respectively connected to the first pin (R) of the constant current source chip (U4).

9. A multi-channel PT temperature measuring device based on analog switches according to claim 7 or 8, characterized in that: The model of the constant current source chip (U4) is LM334MX.

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