Power supply electromotive force and internal resistance measuring circuit

Abstract

The utility model discloses a power supply electromotive force and internal resistance measuring circuit, which comprises a target power supply, a voltage and current measuring unit and a power display unit, and is characterized in that the voltage and current measuring unit measures basic values of the target power supply and inputs the measured values into the power display unit electrically connected with the voltage and current measuring unit; and calculating the obtained numerical value through the power display unit to obtain the output power of the power supply, and displaying the output power. According to the Ohm law of the closed loop, the output power of the power supply is changed along with the change of the external resistance, and when the external resistance of the circuit is equal to the internal resistance of the power supply, the output power of the power supply is maximum. By using the law, the electromotive force and the internal resistance of the power supply can be obtained. According to the measuring method, the tedious step that images need to be drawn in subsequent numerical processing when measuring circuits such as a current voltammetry or a volt-resistance method are used for measuring can be simplified, and the internal resistance and the electromotive force of the power supply can be obtained only by reading the output power of the power supply and performing simple calculation.

Description

Technical Field

[0001] This utility model relates to the field of measuring the electromotive force and internal resistance of a power supply, and specifically to a circuit for measuring the electromotive force and internal resistance of a power supply. Background Technology

[0002] The commonly used method for measuring the electromotive force (EMF) and internal resistance of a DC circuit is the voltmeter-ammeter method. This method involves using a voltmeter and an ammeter to obtain multiple sets of voltage and current values, and then plotting the voltage-current relationship curve (voltmeter-ammeter curve) based on these data. The resistance value is then determined from the voltmeter-ammeter curve (the slope of the curve represents the resistance value), thus determining the EMF and internal resistance of the power supply. Based on this, other methods such as the ammeter-resistance method and the voltmeter-resistance method have been developed. These methods involve connecting an adjustable rheostat and repeatedly changing its resistance value to obtain multiple sets of current and resistance values ​​or voltage and resistance values. Based on the obtained data, a suitable coordinate system is selected to plot the corresponding graph, and the EMF and internal resistance of the power supply are obtained from the ordinate and slope of the curve.

[0003] However, the circuits used in these measurement methods require the measurement personnel to draw graphs after obtaining multiple sets of values, and then perform calculations and judgments based on the graphs. This makes the measurement circuits not simple enough and not convenient enough in practical applications.

[0004] Therefore, there is a need for a power supply electromotive force and internal resistance measurement circuit that can measure the electromotive force and internal resistance of a power supply through simple calculations without the need for image drawing. Utility Model Content

[0005] To address the problems mentioned in the background section, this invention provides a circuit for measuring the electromotive force and internal resistance of a power source. This solves the problem that existing power source electromotive force and internal resistance measurement circuits require image plotting to obtain measurement results, resulting in cumbersome measurement procedures.

[0006] To achieve the above objectives, this utility model provides the following technical solution: a power supply electromotive force and internal resistance measurement circuit, comprising a target power supply, a voltage and current measurement unit, and a power display unit;

[0007] The positive terminal of the target power supply is electrically connected to the positive power supply terminal of the voltage and current measurement unit, the negative power supply terminal of the voltage and current measurement unit is electrically connected to the negative terminal of the target power supply, and the sampling input terminal of the power display unit is electrically connected to the sampling terminal of the voltage and current measurement unit.

[0008] Based on the above-mentioned power supply electromotive force and internal resistance measurement circuit, in one possible design, the voltage and current measurement unit includes a voltmeter, an ammeter, a single-pole double-throw switch, and a resistance adjustment subunit.

[0009] The positive power supply terminal of the ammeter is electrically connected to the positive terminal of the target power supply, and its negative power supply terminal is electrically connected to the negative terminal of the target power supply through the resistor adjustment subunit.

[0010] The negative power supply terminal of the voltmeter is electrically connected to the negative terminal of the target power supply, and its positive power supply terminal is electrically connected to the positive and negative power supply terminals of the ammeter through the single-pole double-throw switch.

[0011] Based on the above-mentioned power supply electromotive force and internal resistance measurement circuit, in one possible design, the resistance adjustment subunit includes a high-precision resistance box.

[0012] The high-precision resistance box is electrically connected between the negative power supply terminal of the ammeter and the negative power supply terminal of the target power source.

[0013] Based on the above-described power supply electromotive force and internal resistance measurement circuit, in one possible design, the sampling terminal of the voltage and current measurement unit includes a voltage sampling terminal and a current sampling terminal, and the sampling input terminal of the power display unit includes a voltage sampling input terminal and a current sampling input terminal.

[0014] Wherein, the two ends of the voltmeter serve as the voltage sampling terminals, and the negative terminal of the target power supply and the negative power supply terminal of the voltage and current measurement unit serve as the current sampling terminals (the negative power supply terminal of the voltage and current measurement unit is the common negative power supply terminal of the voltmeter and the resistance adjustment subunit).

[0015] The voltage sampling input terminal of the power display unit is connected in parallel across the two ends of the voltmeter, and the current sampling input terminal of the power display unit is connected in series between the negative power supply terminal of the voltage and current measurement unit and the negative terminal of the target power supply.

[0016] Based on the above-mentioned power supply electromotive force and internal resistance measurement circuit, a normally open contact switch is also included in one possible design.

[0017] The normally open contact switch is electrically connected between the power display unit and the negative terminal of the target power supply.

[0018] Based on the above-described power supply electromotive force and internal resistance measurement circuit, in one possible design, the power display unit includes a multiplier analog-to-digital converter (ADC) and a display, wherein the ADC is provided with a sampling input terminal of the power display unit, and the digital signal output terminal of the ADC is electrically connected to the display.

[0019] Beneficial effects:

[0020] This utility model discloses a power supply electromotive force and internal resistance measurement circuit, including a target power supply, a voltage and current measurement unit, and a power display unit. The voltage and current measurement unit performs basic numerical measurements on the target power supply and inputs the measured values ​​into the power display unit electrically connected to it. The power display unit calculates the obtained values ​​to obtain the output power of the power supply and displays it. According to Ohm's law for a closed loop, the output power of the power supply changes with the external resistance, and the output power is at its maximum when the external resistance of the circuit equals the internal resistance of the power supply. Using this law, the electromotive force and internal resistance of the power supply can be obtained. This measurement method simplifies the cumbersome steps of subsequent numerical processing, such as plotting graphs, required by existing volt-ampere or volt-resistance measurement circuits. Now, only the output power of the power supply needs to be read and a simple calculation performed to obtain the internal resistance and electromotive force. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a functional block diagram of a power supply electromotive force and internal resistance measurement circuit according to Embodiment 1 of this utility model;

[0023] Figure 2 This is a circuit diagram of the power supply electromotive force and internal resistance measurement circuit in Embodiment 2 of this utility model;

[0024] Figure 3 This is a circuit diagram of the power supply electromotive force and internal resistance measurement circuit in Embodiment 3 of this utility model. Detailed Implementation

[0025] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the present utility model will be briefly introduced below in conjunction with the accompanying drawings and descriptions of the embodiments or the prior art. Obviously, the following description of the structure of the accompanying drawings is only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. It should be noted that the description of these embodiments is used to help understand this utility model, but does not constitute a limitation on this utility model.

[0026] It should be understood that although the terms first, second, etc., may be used herein to describe various units, these units should not be limited by these terms. These terms are only used to distinguish one unit from another. For example, the first unit may be referred to as the second unit, and similarly, the second unit may be referred to as the first unit, without departing from the scope of the embodiments of the invention.

[0027] Specific details are provided in the following description to provide a complete understanding of the exemplary embodiments. However, those skilled in the art will understand that the exemplary embodiments can be implemented without these specific details. For example, the system may be shown in block diagrams to avoid obscuring the example with unnecessary details. In other embodiments, well-known processes, structures, and techniques may be shown without non-essential details to avoid obscuring the embodiments.

[0028] Example 1:

[0029] like Figure 1 As shown, this embodiment provides a power supply electromotive force and internal resistance measurement circuit, including a target power supply, a voltage and current measurement unit, and a power display unit. The target power supply is a DC power supply, preferably a dry cell battery or a rechargeable battery, depending on the actual scenario. The voltage and current measurement unit is designed for the target power supply and can obtain voltage and current parameters related to the target power supply by measuring voltage and current. The power display unit needs to have at least two functions: first, to perform calculations (multiplication calculations) on the acquired digital signals to obtain the required values; second, to digitally display each acquired value for easy reading and recording by the measurement personnel. This power supply electromotive force and internal resistance measurement circuit provided in this embodiment aims to perform relatively accurate measurements on target power supplies with uncertain internal resistance and output electromotive force to obtain their internal resistance and electromotive force for convenient subsequent use; at the same time, it has been optimized based on existing measurement circuits, making the entire measurement work simpler and easier to operate.

[0030] It should be noted that the voltage and current measurement unit mentioned here is not unique in its specific design. It only needs to achieve the purpose of obtaining the voltage and current values ​​related to the target power supply (the voltage and current values ​​are not necessarily the corresponding values ​​of the target power supply, but they need to have a certain correlation and the corresponding values ​​of the target power supply can be obtained through simple calculation). Since this specific design can be implemented by existing measurement circuits, those skilled in the art should be able to obtain a variety of circuit designs that meet the conditions without creative effort. Therefore, it will not be described in detail in this embodiment.

[0031] The positive terminal of the target power supply is electrically connected to the positive power supply terminal of the voltage and current measurement unit, while the negative power supply terminal of the voltage and current measurement unit is electrically connected to the negative terminal of the target power supply. The voltage and current measurement unit operates relative to the target power supply.

[0032] The sampling input terminal of the power display unit is electrically connected to the sampling terminal of the voltage and current measurement unit. The power display unit can acquire the required signal through the sampling input terminal, perform calculations and processing, and display the corresponding value.

[0033] When performing measurements, the target power supply is connected, and the voltage and current measurement unit begins operation. Based on its specific design, the unit obtains the voltage and current values ​​related to the target power supply. After obtaining these values, the unit outputs them to the power display unit via a sampling terminal. The power display unit multiplies the sampled voltage and current values ​​and displays them accordingly. The displayed power reading is P, calculated according to P = I... 2 The internal resistance (r) of the power supply is obtained by r. Then, based on the specific circuit design, the relationship between the voltage reading (U) and the electromotive force (EMF) ε of the power supply is determined. The EMF ε of the power supply is obtained through simple calculation.

[0034] The power supply electromotive force and internal resistance measurement circuit provided in this embodiment can conveniently and quickly obtain the electromotive force and internal resistance of the target power supply through simple calculation and direct reading, without requiring the measurement personnel to perform tedious tasks such as drawing graphs. It is very suitable for application in real life and experimental teaching.

[0035] Example 2:

[0036] like Figure 2 As shown in the figure, this embodiment provides a power supply electromotive force and internal resistance measurement circuit. In a preferred implementation, the voltage and current measurement unit includes a voltmeter, an ammeter, a single-pole double-throw switch, and a resistance adjustment subunit. The positive power supply terminal of the ammeter is electrically connected to the positive terminal of the target power supply, and its negative power supply terminal is electrically connected to the negative terminal of the target power supply through the resistance adjustment subunit. The negative power supply terminal of the voltmeter is electrically connected to the negative terminal of the target power supply, and its positive power supply terminal is electrically connected to both the positive and negative power supply terminals of the ammeter through the single-pole double-throw switch. The voltmeter and ammeter are used to perform corresponding numerical measurements after the resistance adjustment subunit has been adjusted as needed and the single-pole double-throw switch has been placed in the appropriate position, ultimately obtaining the voltage and current values ​​of the target power supply.

[0037] The resistance adjustment subunit includes a high-precision resistance box; the high-precision resistance box is electrically connected between the negative power supply terminal of the ammeter and the negative power supply terminal of the target power supply. The high-precision resistance box referred to here is an adjustable resistance box with a resistance adjustment accuracy of 0.01Ω. This is to ensure its continuous adjustability as much as possible, thereby ensuring the accurate determination of the maximum output power of the target power supply.

[0038] The sampling terminals of the voltage and current measurement unit include voltage sampling terminals and current sampling terminals, while the sampling input terminals of the power display unit include voltage sampling input terminals (pins 3 and 4) and current sampling input terminals (pins 1 and 2). The voltage sampling input terminal of the power display unit is connected in parallel across the voltmeter, and the current sampling input terminal is connected in series between the output terminal of the current measurement circuit and the negative terminal of the target power supply. For the voltmeter and ammeter in the voltage and current measurement unit, the power display unit is equipped with voltage sampling input terminals and current sampling input terminals respectively, used to acquire the measurement results from the voltmeter and ammeter.

[0039] It also includes a normally open contact switch; the normally open contact switch is electrically connected between the power display unit and the negative terminal of the target power supply. The normally open contact switch (preferably a common single-pole single-throw switch or a push-button contact switch) is provided to offer a certain degree of controllability and experimental safety for the measurement circuit provided in this embodiment. Specifically, when the normally open contact switch is normally open, connecting the target power supply will not immediately energize the entire circuit. The normally open contact switch can be closed at any time as needed to control the circuit operation; furthermore, there is no risk of electric shock when the measurement personnel connect the target power supply, making the overall circuit more practical and safer.

[0040] The power display unit includes a multiplier analog-to-digital converter (ADC) and a display. The ADC has a sampling input terminal for the power display unit, and its digital signal output terminal is electrically connected to the display. The ADC performs analog-to-digital conversion on the acquired analog signal and multiplies the resulting digital signal (U, I) by a multiplication operation, i.e., U × I. The calculated result (P) and the converted digital signal (U, I) are then sent to the display for digital display.

[0041] Among them, the multiplication analog-to-digital converter can preferably be a dual 8-bit multiplication analog-to-digital converter such as TLC7528C, TLC7528E or TLC7528I to ensure higher computing power and calculation accuracy.

[0042] When performing measurements, open the normally open contact switch, adjust the high-precision resistance box to its maximum resistance value, connect the target power supply, throw the single-pole double-throw switch to point a, close the normally open contact switch, and the voltage and current measuring unit will start working. At this time, the voltage reading on the display is U1, the current reading on the display is I1, and the reading of the high-precision resistance box is R1. The internal resistance of the ammeter (R) can be obtained. A )for:

[0043] Next, switch the double-throw switch to point b, and then gradually decrease the resistance of the high-precision resistance box. Observe on the display that the power reading P (output power of the target power supply) first increases, then begins to decrease after reaching a certain point. At this time, repeatedly fine-tune the resistance box to find the position of the maximum power reading. Read the voltage reading at this time from the display as U2 (voltage of the high-precision resistance box), and the reading of the high-precision resistance box as R2. When the external resistance equals the internal resistance of the target power supply, the output power of the power supply is the maximum. Using this law, we know that the electromotive force ε of the power supply is: ε = 2U2, and the internal resistance r of the power supply is...

[0044] Example 3:

[0045] like Figure 3 As shown, this embodiment provides a power supply electromotive force and internal resistance measurement circuit. As a preferred implementation, a digital display LCD DC dual display digital detector is used to replace the ammeter, voltmeter and power display unit. Pins 1 and 2 are the current acquisition input terminals of the digital display LCD DC dual display digital detector; pins 3 and 4 are the voltage acquisition input terminals of the digital display LCD DC dual display digital detector.

[0046] When performing measurements, disconnect the normally open contact switch, connect the target power supply, and adjust the high-precision resistance box until the power reading on the digital display LCD DC dual display digital detector reaches its maximum value. Then, read the voltage reading and the resistance value of the high-precision resistance box at this time, and calculate the electromotive force and internal resistance of the power supply at this time through the voltage and current readings.

[0047] Finally, it should be noted that the above are merely preferred embodiments of this utility model and are not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A power source electromotive force and internal resistance measuring circuit characterized by comprising: The target power supply, a voltage and current measurement unit, and a power display unit are included. The positive electrode of the target power supply is electrically connected to the positive power supply end of the voltage and current measurement unit, and the negative power supply end of the voltage and current measurement unit is electrically connected to the negative electrode of the target power supply. The voltage and current measurement unit includes a voltmeter, an ammeter, a single-pole double-throw switch, and a resistance adjustment subunit. The positive power supply end of the ammeter is electrically connected to the positive electrode of the target power supply, and the negative power supply end is electrically connected to the negative electrode of the target power supply through the resistance adjustment subunit. The negative power supply end of the voltmeter is electrically connected to the negative electrode of the target power supply, and the positive power supply end is electrically connected to the positive power supply end and the negative power supply end of the ammeter through the single-pole double-throw switch. The resistance adjustment subunit includes a high-precision resistance box. The high-precision resistance box is electrically connected between the negative power supply end of the ammeter and the negative power supply end of the target power supply. The sampling end of the voltage and current measurement unit includes a voltage sampling end and a current sampling end, and the sampling input end of the power display unit includes a voltage sampling input end and a current sampling input end. The two ends of the voltmeter serve as the voltage sampling end, and the negative electrode of the target power supply and the negative power supply end of the voltage and current measurement unit serve as the current sampling end. The voltage sampling input end of the power display unit is connected in parallel across the two ends of the voltmeter, and the current sampling input end of the power display unit is connected in series between the negative power supply end of the voltage and current measurement unit and the negative electrode of the target power supply. A normally open contact switch is also included. The normally open contact switch is electrically connected between the power display unit and the negative electrode of the target power supply. The power display unit includes a multiplication analog-to-digital converter and a display, wherein the sampling input end of the power display unit is provided with the multiplication analog-to-digital converter, and the digital signal output end of the multiplication analog-to-digital converter is electrically connected to the display.

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