Self-adaptive frequency measurement circuit and method and universal meter
By designing an adaptive frequency measurement circuit in the multimeter, and automatically divide the voltage or disconnect the voltage divider circuit according to the voltage value, the unreliable and erroneous operation problems of the multimeter when measuring different voltage frequencies is solved, and more accurate and convenient frequency measurement is achieved.
Patent Information
- Application Number
- CN202411569085.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-05
- Publication Date
- 2025-02-25
AI Technical Summary
When measuring frequencies of different voltages, existing multimeters have problems such as unreliable measurement results and easy to operate incorrectly.
An adaptive frequency measurement circuit is designed to detect the input voltage of the circuit after voltage division and compare it with the specified threshold. When the voltage is large, divide the input voltage to prevent the voltage from being too high, which makes the measurement result unreliable; when the voltage is small, disconnect the voltage divider circuit and directly perform frequency measurement, ensuring the accuracy of the frequency measurement of low voltages.
Through the adaptive frequency measurement circuit, the problem of unreliable measurement results at high voltage is solved, while ensuring the accuracy of frequency measurement at low voltage is ensured, and misoperation is avoided.
Smart Images
Figure CN119510885A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of frequency measurement of voltage of a multimeter, and in particular to an adaptive frequency measurement circuit, method and multimeter. Background Art
[0002] The traditional pointer multimeter measures the internal circuit of AC, which involves some non-pure resistance elements, such as the pointer coil of the pointer meter. Therefore, the calibration of the pointer multimeter uses a certain frequency and a certain waveform of AC as the standard calibration. This is why the multimeter can measure 50Hz sine wave AC more accurately. Ordinary multimeters can only measure signal voltages below audio. If the frequency exceeds this too much, the reading error will be relatively large. If it is used to measure AC with higher frequency and waveform, the reading will be inaccurate.
[0003] The frequency measurement circuit of the traditional multimeter voltage is unreliable when measuring the frequency of high voltage. In order to solve this problem, a voltage divider circuit is added to the frequency measurement circuit, but this reduces the sensitivity and the low voltage frequency cannot be measured.
[0004] The common practice of current multimeters is to set two frequency measurement gears and manually switch the corresponding frequency measurement gears for different voltages, which is inconvenient to use and prone to misoperation. Summary of the invention
[0005] In the prior art, when a multimeter measures the frequencies of different voltages, there are problems such as unreliable measurement results and easy misoperation.
[0006] In view of the above problems, an adaptive frequency measurement circuit, method and multimeter are proposed. The circuit input voltage after voltage division is detected and compared with the specified threshold value. When the voltage is large, the input voltage is divided to prevent the measurement result from being unreliable due to excessive voltage. When the voltage is small, the voltage division circuit is disconnected and the frequency measurement is performed directly, thereby ensuring the accuracy of low voltage frequency measurement.
[0007] In a first aspect, an adaptive frequency measurement circuit includes: A first protection module; The second protection module; Voltage divider module; Select the module; Voltage measurement module; Frequency measurement module; Control module; The first protection module is electrically connected to the voltage input terminal, the voltage dividing module, the second protection module, and the selection module respectively; The voltage dividing module is also electrically connected to the selection module and the voltage measuring module; The second protection module is also electrically connected to the frequency measurement module and the common terminal; The selection module is also electrically connected to the control module and the frequency measurement module; The voltage measurement module is also electrically connected to the control module; The frequency measurement module is also electrically connected to the common terminal and the control module.
[0008] In conjunction with the adaptive frequency measurement circuit described in the first aspect of the present invention, in a first possible implementation manner, the first protection module includes: Thermistor First switch; The first end of the thermistor is electrically connected to the voltage input end and the voltage divider module, and the second end is electrically connected to the input end of the first switch; The output end of the first switch is electrically connected to the selection module and the second protection module.
[0009] In combination with the first possible implementation manner of the first aspect of the present invention, in a second possible implementation manner, the second protection module includes: The first triode; The second triode; The source of the first transistor is electrically connected to the output end of the first switch and the selection module, the gate and drain of the first transistor are electrically connected to the gate and drain of the second transistor respectively, and the source of the second transistor is connected to the frequency measurement module and the common end and then grounded.
[0010] In combination with the second possible implementation manner of the first aspect of the present invention, in a third possible implementation manner, the voltage division module includes: A first resistor and a second resistor; The first end of the first resistor is electrically connected to the voltage input end and the first end of the thermistor, and the second end is electrically connected to the first end of the second resistor, the voltage measurement module and the selection module; A second terminal of the second resistor is grounded.
[0011] In combination with the third possible implementation manner of the first aspect of the present invention, in a fourth possible implementation manner, the selection module includes: Second switch; The third switch; The input end of the second switch is electrically connected to the output end of the first switch and the source of the first transistor, and the output end of the second switch is electrically connected to the frequency measurement module; An input end of the third switch is electrically connected to the second end of the first resistor, the first end of the second resistor and the voltage measurement module, and an output end of the third switch is electrically connected to the frequency measurement module.
[0012] In combination with the fourth possible implementation manner of the first aspect of the present invention, in a fifth possible implementation manner, the control module includes: Control chip; The control chip comprises: A first enable pin, a second enable pin and a third enable pin; The first enable pin, the second enable pin and the third enable pin are electrically connected to the control coil of the first switch, the control coil of the second switch and the control coil of the third switch respectively.
[0013] In a second aspect, an adaptive frequency measurement method is provided, using the adaptive frequency measurement circuit described in the first aspect, comprising: Step 100: Perform voltage detection on the voltage dividing module to obtain an input voltage value, and transmit the input voltage value to the control module; Step 200: the control module compares the input voltage value with a set threshold value; Step 300: If the input voltage value is greater than the threshold value, close the third switch to perform frequency measurement; Step 400: If the input voltage value is less than or equal to the threshold, close the second switch to perform frequency measurement.
[0014] In conjunction with the adaptive frequency measurement method described in the second aspect of the present invention, in a first possible implementation manner, between closing the third switch and performing the frequency measurement, the method includes: Step 310: Turn off the first switch to disconnect the electrical connection between the voltage input terminal and the second protection module and the frequency measurement module.
[0015] In combination with the first possible implementation manner of the second aspect of the present invention, in a second possible implementation manner, closing the third switch includes: Step 320: The control chip of the control module outputs an enable signal to the third enable terminal, and turns on the coil of the third switch according to the enable signal to close the third switch.
[0016] In a third aspect, a multimeter is provided, which performs frequency measurement using the adaptive frequency measurement method described in the second aspect.
[0017] The adaptive frequency measurement circuit, method and multimeter described in the present invention are implemented by detecting the circuit input voltage after voltage division and comparing it with a specified threshold value. When the voltage is large, the input voltage is divided to prevent the voltage from being too high and causing unreliable measurement results. When the voltage is small, the voltage division circuit is disconnected and the frequency measurement is performed directly, thereby ensuring the accuracy of low voltage frequency measurement. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0019] Figure 1 Schematic diagram of the module structure of the adaptive frequency measurement circuit in the present invention; Figure 2 Schematic diagram of the circuit structure of the adaptive frequency measurement circuit in the present invention; Figure 3 It is a circuit structure diagram of a control chip in the adaptive frequency measurement circuit of the present invention; Figure 4 Schematic diagram of the process flow of the adaptive frequency measurement method in the present invention.
[0020] Components and their serial numbers: 100 —a first protection module, 200 —a voltage dividing module, 300 —a selection module, 400 —a voltage measuring module, 500 —a control module, 600 —a frequency measuring module, 700 —a second protection module. DETAILED DESCRIPTION
[0021] The following will be combined with the accompanying drawings in the invention to clearly and completely describe the technical solutions in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention.
[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.
[0023] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.
[0024] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.
[0025] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.
[0026] In the prior art, when a multimeter measures the frequencies of different voltages, there are problems such as unreliable measurement results and easy misoperation.
[0027] In view of the above problems, an adaptive frequency measurement circuit, method and multimeter are proposed.
[0028] In a first aspect, an adaptive frequency measurement circuit, such as Figure 1 , Figure 1 The schematic diagram of the module structure of the adaptive frequency measurement circuit in the present invention includes a first protection module 100 , a second protection module 700 , a voltage dividing module 200 , a selection module 300 , a voltage measurement module 400 , a frequency measurement module 600 , and a control module 500 .
[0029] The structure of the frequency measurement circuit is: The first protection module 100 is electrically connected to the voltage input terminal, the voltage dividing module 200, the second protection module 700, and the selection module 300 respectively; the voltage dividing module 200 is also electrically connected to the selection module 300 and the voltage measuring module 400; the second protection module 700 is also electrically connected to the frequency measuring module 600 and the common terminal; the selection module 300 is also electrically connected to the control module 500 and the frequency measuring module 600; the voltage measuring module 400 is also electrically connected to the control module 500; the frequency measuring module 600 is also electrically connected to the common terminal and the control module 500.
[0030] The first protection module 100 is mainly used to perform thermal protection on the input circuit, and the voltage divider module 200 is used to divide the input voltage to prevent unreliable frequency measurement. The second protection module 700 is mainly used to protect the frequency measurement module 600, and the selection module 300 is used to select the corresponding branch to be connected to the frequency measurement module 600 according to the instruction of the control module 500, so as to perform frequency measurement.
[0031] The voltage measurement module 400 measures the voltage of the branch and sends the measured value to the control module 500 for determination.
[0032] The control module 500 is used to obtain the voltage input after the measured voltage division, and compare it with the specified threshold value, and output the corresponding instruction according to the comparison result, and turn on the corresponding switch to measure the frequency. By detecting the circuit input voltage after voltage division and comparing it with the specified threshold value, when the voltage is large, the input voltage is divided to prevent the voltage from being too high and causing unreliable measurement results. When the voltage is small, the voltage division circuit is disconnected and the frequency measurement is performed directly, thereby ensuring the accuracy of low voltage frequency measurement.
[0033] In order to provide thermal protection for the input circuit, such as Figure 2 , Figure 2 FIG. 1 is a schematic diagram of the circuit structure of the adaptive frequency measurement circuit in the present invention. The first protection module 100 in this embodiment includes a thermistor R L , the first switch K1; the circuit structure of the first protection module 100 is: Thermistor R L The first end is electrically connected to the voltage input end and the voltage dividing module 200 , and the second end is electrically connected to the input end of the first switch K1 ; the output end of the first switch K1 is electrically connected to the selection module 300 and the second protection module 700 .
[0034] In order to perform thermal protection on the input circuit, the second protection module 700 in this embodiment includes a first transistor Q1 and a second transistor Q2; the circuit structure of the second protection module 700 is: The source of the first transistor Q1 is electrically connected to the output end of the first switch K1 and the selection module 300, the gate and drain of the first transistor Q1 are electrically connected to the gate and drain of the second transistor Q2 respectively, and the source of the second transistor Q2 is connected to the frequency measurement module 600 and the common end and then grounded.
[0035] In order to divide the input voltage, the voltage dividing module 200 in this embodiment includes: a first resistor R1 and a second resistor R2; the circuit structure of the voltage dividing module 200 is: The first end of the first resistor R1 is connected to the voltage input end and the thermistor R L The first end of the resistor R2 is electrically connected to the first end of the resistor R2, the voltage measuring module 400 and the selecting module 300; the second end of the resistor R2 is grounded.
[0036] In order to adaptively select the corresponding branch for frequency measurement, the selection module 300 in this embodiment includes a second switch K2 and a third switch K3; the circuit structure of the selection module 300 is: The input end of the second switch K2 is electrically connected to the output end of the first switch K1 and the source of the first transistor Q1, and the output end of the second switch K2 is electrically connected to the frequency measurement module 600; the input end of the third switch K3 is electrically connected to the second end of the first resistor R1, the first end of the second resistor R2 and the voltage measurement module 400, and the output end of the third switch K3 is electrically connected to the frequency measurement module 600.
[0037] like Figure 3 , Figure 3 Schematic diagram of the circuit structure of the control chip U1 in the adaptive frequency measurement circuit of the present invention; the control module 500 in this embodiment includes: the control chip U1; the control chip U1 includes: a first enable pin EN1, a second enable pin EN2 and a third enable pin EN3; the first enable pin EN1, the second enable pin EN2 and the third enable pin EN3 are electrically connected to the control coil of the first switch K1, the control coil of the second switch K2 and the control coil of the third switch K3 respectively.
[0038] like Figure 3 The control chip U1 also includes pins (PIN1, PIN2) for connecting to the voltage measurement module 400 and the frequency measurement module 600.
[0039] The principle of the control chip U1 controlling the selection module 300 to select a branch for frequency measurement is: The input voltage is divided by the voltage divider module 200, and the voltage measurement module 400 measures the divided voltage and transmits the measured value to the control chip U1. The control chip U1 compares the measured value with the set threshold value. If it is greater than the specified threshold value, a high-level enable signal is sent to the third enable pin EN3 to energize the control coil of the third switch KE, and at the same time, a low-level enable signal is sent to the first enable pin EN1 to de-energize the control coil of the first switch K1. After the control coil of the third switch K3 is energized, the third switch K3 is closed, so that the voltage divider module 200 and the frequency measurement module 600 are turned on to perform frequency measurement.
[0040] If it is less than the specified threshold, a high-level enable signal is sent to the second enable pin EN2 to turn on the control coil of the second switch K2. At the same time, a high-level enable signal is sent to the first enable pin EN1 to turn on the control coil of the first switch K1. After the first switch K1 is turned on and the control coil of the second switch K2 is energized, the second switch K2 is closed, so that the input circuit is turned on with the frequency measurement module 600 to perform frequency measurement.
[0041] Second, as Figure 4 , Figure 41 is a schematic diagram of the steps of the adaptive frequency measurement method of the present invention. An adaptive frequency measurement method adopts the adaptive frequency measurement electrical connection of the first aspect, comprising: Step 100, perform voltage detection on the voltage divider module, obtain the input voltage value, and transmit the input voltage value to the control module 500; Step 200, the control module 500 compares the input voltage value with the set threshold value; Step 300, if the input voltage value is greater than the threshold value, close the third switch K3 and perform frequency measurement; Step 400, if the input voltage value is less than or equal to the threshold value, close the second switch K2 and perform frequency measurement.
[0042] Preferably, between closing the third switch K3 and performing the frequency measurement, the following steps are included: Step 310 , opening the first switch K1 to disconnect the electrical connection between the voltage input terminal and the second protection module 700 and the frequency measurement module 600 .
[0043] Preferably, closing the third switch K3 includes: step 320, the control chip U1 of the control module 500 outputs an enable signal at the third enable terminal EN3, and turns on the coil of the third switch K3 according to the enable signal to close the third switch K3.
[0044] In a third aspect, a multimeter adopts the adaptive frequency measurement method of the second aspect to perform frequency measurement.
[0045] The adaptive frequency measurement circuit, method and multimeter of the present invention detect the circuit input voltage after voltage division and compare it with a specified threshold value. When the voltage is large, the input voltage is divided to prevent the voltage from being too high and causing unreliable measurement results. When the voltage is small, the voltage division circuit is disconnected and the frequency measurement is performed directly, thereby ensuring the accuracy of low voltage frequency measurement.
[0046] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. An adaptive frequency measurement circuit, characterized in that it includes: A first protection module; The second protection module; Voltage divider module; Select the module; Voltage measurement module; Frequency measurement module; Control module; The first protection module is electrically connected to the voltage input terminal, the voltage dividing module, the second protection module, and the selection module respectively; The voltage dividing module is also electrically connected to the selection module and the voltage measuring module; The second protection module is also electrically connected to the frequency measurement module and the common terminal; The selection module is also electrically connected to the control module and the frequency measurement module; The voltage measurement module is also electrically connected to the control module; The frequency measurement module is also electrically connected to the control module.
2. The adaptive frequency measurement circuit according to claim 1, characterized in that: The first protection module includes: Thermistor First switch; The first end of the thermistor is electrically connected to the voltage input end and the voltage divider module, and the second end is electrically connected to the input end of the first switch; The output end of the first switch is electrically connected to the selection module and the second protection module.
3. The adaptive frequency measurement circuit according to claim 2, characterized in that: The second protection module comprises: The first triode; The second triode; The source of the first transistor is electrically connected to the output end of the first switch and the selection module, the gate and drain of the first transistor are electrically connected to the gate and drain of the second transistor respectively, and the source of the second transistor is connected to the frequency measurement module and the common end and then grounded.
4. The adaptive frequency measurement circuit according to claim 3, characterized in that: The voltage divider module comprises: A first resistor and a second resistor; The first end of the first resistor is electrically connected to the voltage input end and the first end of the thermistor, and the second end is electrically connected to the first end of the second resistor, the voltage measurement module and the selection module; A second terminal of the second resistor is grounded.
5. The adaptive frequency measurement circuit according to claim 4, characterized in that: The selection module comprises: Second switch; The third switch; The input end of the second switch is electrically connected to the output end of the first switch and the source of the first transistor, and the output end of the second switch is electrically connected to the frequency measurement module; An input end of the third switch is electrically connected to the second end of the first resistor, the first end of the second resistor and the voltage measurement module, and an output end of the third switch is electrically connected to the frequency measurement module.
6. The adaptive frequency measurement circuit according to claim 5, characterized in that: The control module comprises: Control chip; The control chip comprises: A first enable pin, a second enable pin and a third enable pin; The first enable pin, the second enable pin and the third enable pin are electrically connected to the control coil of the first switch, the control coil of the second switch and the control coil of the third switch respectively.
7. An adaptive frequency measurement method, using the adaptive frequency measurement circuit according to any one of claims 1 to 6, characterized in that: include: Step 100: Perform voltage detection on the voltage dividing module to obtain an input voltage value, and transmit the input voltage value to the control module; Step 200: the control module compares the input voltage value with a set threshold value; Step 300: If the input voltage value is greater than the threshold value, close the third switch to perform frequency measurement; Step 400: If the input voltage value is less than or equal to the threshold, close the second switch to perform frequency measurement.
8. The adaptive frequency measurement method according to claim 7, characterized in that: Between closing the third switch and performing frequency measurement, the method includes: Step 310: Turn off the first switch to disconnect the electrical connection between the voltage input terminal and the second protection module and the frequency measurement module.
9. The adaptive frequency measurement method according to claim 8, characterized in that: The closing of the third switch comprises: Step 320: The control chip of the control module outputs an enable signal to the third enable terminal, and turns on the coil of the third switch according to the enable signal to close the third switch.
10. A multimeter, characterized in that: The frequency measurement is performed using the adaptive frequency measurement method described in any one of claims 7 to 9.