Discharge capacity measuring device
By designing a measuring device that includes components such as power supply, constant current circuit, op-amp circuit, timer, etc., the battery being tested is directly discharged in a constant current and recorded the discharge time, which solves the problem of low efficiency caused by the cumbersome test methods, and achieves more efficient and accurate battery capacity testing.
Patent Information
- Application Number
- CN202421550292.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-02
- Publication Date
- 2025-06-06
- Estimated Expiration
- 2034-07-02
AI Technical Summary
The existing lithium battery capacity testing methods are cumbersome, the equipment occupancy rate is high, and the external lengthened wire impedance is large, resulting in large current errors, increasing test errors and low test efficiency.
A measurement device including a power supply, a constant current circuit, an operational amplifier circuit, a timer, a positive electrode input terminal and a negative electrode input terminal is designed. The battery to be tested is directly discharged through a constant current circuit, and the discharge time is recorded through a timer to calculate the discharge capacity.
It reduces the cumbersomeness of the test method, improves the accuracy of the test results, improves the testing efficiency, and solves the problem of low testing efficiency caused by the cumbersome battery capacity testing methods.
Smart Images
Figure CN222952465U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of batteries, and in particular to a discharge capacity measuring device. Background Art
[0002] The RTC (Real Time Clock) function of lithium battery projects is becoming increasingly popular, and verification of RTC capacity is also necessary. The current RTC capacity test method is: first discharge the lithium battery at 0.5C to RSOC=0%, then discharge the lithium battery to an undervoltage state with 100mA, connect the lithium battery to a charge and discharge cabinet, set the static step log lithium battery voltage data, and set an external high-precision load to discharge at 2mA. When the lithium battery voltage of the aging cabinet log drops to 2.5V, the protection IC (integrated circuit) will turn off the lithium battery and stop discharging. The lithium battery voltage drops to 0V, and the lithium battery is judged to be empty. The time Δt when the voltage drops to 0V is calculated, and it is qualified if it is ≥30h. The RTC capacity can be calculated through the formula C=I·Δt. This test method requires placing the battery in an incubator and connecting it to a charging and discharging cabinet, then moving the high-precision load to the incubator area and externally extending the wire. The test method is cumbersome, the equipment occupancy rate is high, and the impedance of the external extension wire is greater, resulting in large current errors, increased test errors, and low test efficiency. Utility Model Content
[0003] The present application provides a discharge capacity measuring device to solve the technical problem that the current battery capacity testing method is cumbersome and leads to low testing efficiency.
[0004] The present application provides a discharge capacity measuring device, comprising: a power supply, a constant current circuit, an operational amplifier circuit, a timer, a positive input terminal and a negative input terminal, wherein the positive input terminal is used to be connected to the positive electrode of a battery under test, the negative input terminal is used to be connected to the negative electrode of the battery under test, the first end of the constant current circuit is connected to the positive input terminal, the second end of the constant current circuit is connected to the negative input terminal, the third end of the constant current circuit is connected to the first end of the operational amplifier circuit, the fourth end of the constant current circuit is connected to the first end of the timer, the second end of the operational amplifier circuit is connected to the first end of the power supply, and the second end of the power supply is connected to the second end of the timer.
[0005] As an optional example, the measuring device further includes: a power switch, wherein the first end of the power switch is connected to the second end of the power supply, the second end of the power switch is connected to the second end of the timer, and the timer is used to start timing when the power switch is turned on, and stop timing when the measured battery is discharged.
[0006] As an optional example, the above-mentioned constant current circuit includes: a constant current driving chip, the first end of the above-mentioned constant current driving chip is connected to the above-mentioned positive input end, the second end of the above-mentioned constant current driving chip is connected to the above-mentioned negative input end, the third end of the above-mentioned constant current driving chip and the fourth end of the above-mentioned constant current driving chip are connected to the first end of the above-mentioned operational amplifier circuit, the fifth end of the above-mentioned constant current driving chip, the sixth end of the above-mentioned constant current driving chip, the seventh end of the above-mentioned constant current driving chip and the eighth end of the above-mentioned constant current driving chip are connected to the ground.
[0007] As an optional example, the constant current driving chip includes: an LED lamp, which is used to light up when the power switch is turned on, and turn off when the tested battery is discharged.
[0008] As an optional example, the above-mentioned constant current circuit also includes: a first diode, a second diode and a transient suppression diode, the first end of the above-mentioned first diode is connected to the sixth end of the above-mentioned constant current driving chip, the second end of the above-mentioned first diode is connected to the seventh end of the above-mentioned constant current driving chip, the first end of the above-mentioned second diode is respectively connected to the third end of the above-mentioned constant current driving chip and the fourth end of the above-mentioned constant current driving chip, the second end of the above-mentioned second diode is connected to the first end of the above-mentioned operational amplifier circuit, the first end of the above-mentioned transient suppression diode is respectively connected to the third end of the above-mentioned constant current driving chip and the fourth end of the above-mentioned constant current driving chip, and the second end of the above-mentioned transient suppression diode is connected to ground.
[0009] As an optional example, the constant current circuit further includes: a first resistor, wherein the first end of the first resistor is respectively connected to the seventh end of the constant current driving chip and the second end of the first diode, and the second end of the first resistor is connected to the ground.
[0010] As an optional example, the resistance of the first resistor is determined by the input voltage and output current of the constant current driving chip.
[0011] As an optional example, the constant current circuit further includes a capacitor, wherein a first end of the capacitor is connected to the eighth end of the constant current driving chip, and a second end of the capacitor is connected to the ground.
[0012] As an optional example, the operational amplifier circuit includes: an operational amplifier, a second resistor and a third resistor, the output end of the operational amplifier is respectively connected to the third end of the constant current circuit and the first end of the second resistor, the inverting input end of the operational amplifier is respectively connected to the second end of the second resistor and the first end of the third resistor, the positive input end of the operational amplifier is connected to the first end of the power supply, and the second end of the third resistor is connected to the ground.
[0013] As an optional example, the operational amplifier is used to convert the low voltage of the power supply into a high voltage and then input it into the constant current drive chip.
[0014] In an embodiment of the present application, a power supply, a constant current circuit, an operational amplifier circuit, a timer, a positive input terminal and a negative input terminal are used. The positive input terminal is used to be connected to the positive electrode of the battery under test, and the negative input terminal is used to be connected to the negative electrode of the battery under test. The first end of the constant current circuit is connected to the positive input terminal, the second end of the constant current circuit is connected to the negative input terminal, the third end of the constant current circuit is connected to the first end of the operational amplifier circuit, the fourth end of the constant current circuit is connected to the first end of the timer, the second end of the operational amplifier circuit is connected to the first end of the power supply, and the fourth end of the constant current circuit is connected to the first end of the timer. The test device has two ends connected to the second end of the above-mentioned timer. In the above-mentioned test device, a constant current test circuit is composed of a power supply, a constant current circuit, an operational amplifier circuit, a timer, a positive input terminal and a negative input terminal. The constant current test circuit directly performs constant current discharge on the battery under test, and the discharge time of the battery under test can be recorded by the timer, and finally the discharge capacity of the battery under test is calculated, thereby achieving the purpose of reducing the cumbersomeness of the original test method, improving the accuracy of the test results, and improving the test efficiency, thereby solving the technical problem that the current battery capacity test method is cumbersome and leads to low test efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.
[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.
[0017] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.
[0018] Figure 1 is a schematic structural diagram of an optional discharge capacity measuring device according to an embodiment of the present application;
[0019] Figure 2 This is a circuit connection diagram of an optional discharge capacity measuring device according to an embodiment of the present application. DETAILED DESCRIPTION
[0020] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.
[0021] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed.
[0022] According to a first aspect of an embodiment of the present application, a discharge capacity measuring device is provided, optionally, as Figure 1 As shown, the above device comprises:
[0023] A power supply 102, a constant current circuit 104, an operational amplifier circuit 106, a timer 108, a positive input terminal 109 and a negative input terminal 110, wherein the positive input terminal is used to be connected to the positive electrode of the battery under test, the negative input terminal is used to be connected to the negative electrode of the battery under test, a first end of the constant current circuit is connected to the positive input terminal, a second end of the constant current circuit is connected to the negative input terminal, a third end of the constant current circuit is connected to the first end of the operational amplifier circuit, a fourth end of the constant current circuit is connected to the first end of the timer, a second end of the operational amplifier circuit is connected to the first end of the power supply, and a second end of the power supply is connected to the second end of the timer.
[0024] Optionally, the current existing RTC capacity test method needs to put the tested battery into a thermostat and connect the charging and discharging cabinet, and then move the high-precision load to the thermostat area, and extend the wire externally. The test method is cumbersome, the equipment occupancy rate is high, and the impedance of the external extension wire is larger, resulting in large current error, increased test error, and low test efficiency. Therefore, the measuring device in this embodiment includes a power supply, an operational amplifier circuit, a constant current circuit, a timer, a positive input terminal, and a negative input terminal. The first end of the constant current circuit is connected to the positive input terminal, the second end of the constant current circuit is connected to the negative input terminal, the third end of the constant current circuit is connected to the first end of the operational amplifier circuit, the fourth end of the constant current circuit is connected to the first end of the timer, the second end of the operational amplifier circuit is connected to the first end of the power supply, and the second end of the power supply is connected to the second end of the timer. The operational amplifier circuit mainly adjusts the input voltage of the constant current circuit for the normal operation of the constant current circuit. The constant current circuit can achieve a 2mA constant current output through an external resistor. The timer can use a 555 timer, which can record the working time of the circuit, and then calculate the discharge capacity of the tested battery by time. Specifically, the battery under test is connected to the positive input terminal and the negative input terminal, and the constant current circuit discharges the battery port under test with a constant current of 2mA. The timer starts timing. When the capacity of the battery under test is emptied, the timer stops timing. The time displayed by the timer is used to record the working time of the circuit, that is, the discharge time of the battery under test. The discharge capacity of the resistor under test is calculated through the discharge time.
[0025] Optionally, in this embodiment, the power supply, the constant current circuit, the operational amplifier circuit, the timer, the positive input terminal and the negative input terminal constitute a constant current test circuit, through which the battery under test is directly discharged at a constant current, and the discharge time of the battery under test can be recorded by the timer, and finally the discharge capacity of the battery under test is calculated, thereby reducing the complexity of the original test method, improving the accuracy of the test results, and improving the test efficiency, thereby solving the technical problem that the current battery capacity test method is cumbersome and leads to low test efficiency.
[0026] As an optional example, the above-mentioned measuring device further includes:
[0027] A power switch, wherein a first end of the power switch is connected to a second end of a power source, and a second end of the power switch is connected to a second end of a timer, wherein the timer is used to start timing when the power switch is turned on, and stop timing when the discharge of the tested battery is completed.
[0028] Optionally, in this embodiment, the measuring device further includes a power switch, which can be arranged between the power supply and the timer. After the measured battery is connected to the positive input terminal and the negative input terminal, the power switch is turned on, the constant current circuit discharges the measured battery port with a constant current of 2 mA, and the timer starts timing. When the capacity of the measured battery is emptied, the timer stops timing, and the working time of the circuit is recorded by the time displayed by the timer, that is, the discharge time of the measured battery, and then the discharge capacity of the measured resistor is calculated by the discharge time.
[0029] As an optional example, the constant current circuit includes:
[0030] A constant current drive chip, a first end of the constant current drive chip is connected to the positive input end, a second end of the constant current drive chip is connected to the negative input end, a third end of the constant current drive chip and a fourth end of the constant current drive chip are connected to the first end of the operational amplifier circuit, and a fifth end of the constant current drive chip, a sixth end of the constant current drive chip, a seventh end of the constant current drive chip and an eighth end of the constant current drive chip are connected to ground.
[0031] Optionally, in this embodiment, if Figure 2 As shown in the circuit connection diagram, the constant current circuit includes a constant current driver chip, the first end X1 of the constant current driver chip is connected to the positive input end, the second end X2 of the constant current driver chip is connected to the negative input end, the third end I of the constant current driver chip and the fourth end PWN of the constant current driver chip are connected to the first end of the operational amplifier circuit, the fifth end GND of the constant current driver chip, the sixth end Q of the constant current driver chip, the seventh end REF of the constant current driver chip and the eighth end D of the constant current driver chip are connected to the ground. The constant current driver chip can use the TL4242 chip, or other constant current driver chips with the same function. The TL4242 chip is an LED constant current driver chip with an internal integrated switch tube and a constant current control circuit. The output current can be controlled by adjusting the resistance value of the external resistor to achieve LED constant current drive. The operational amplifier circuit is used to convert the fixed input voltage of the power supply into a high voltage input to the TL4242 constant current driver chip. The resistance value of the external resistor can be calculated according to the constant current voltage and constant current defined by the TL4242 constant current driver chip, so as to achieve constant current control. For example, the operational amplifier circuit converts the fixed input voltage of 3V of the power supply into an input voltage of 9V and gives it to the TL4242 constant current driver chip. The TL4242 constant current driver chip defines the output voltage VRefmax = 0.185V, the output current I = 2mA, and the resistance value of the external resistor Ref = 92.5Ω can be obtained by calculating V = IR, thereby achieving constant current control.
[0032] As an optional example, the constant current driver chip includes:
[0033] LED light: When the power switch is turned on, the LED light will light up, and when the battery under test is discharged, the LED light will go out.
[0034] Optionally, in this embodiment, there is an LED light on the constant current driver chip. After the battery under test is connected to the positive input terminal and the negative input terminal, the power switch is turned on, the LED light of the constant current driver chip lights up, and the constant current driver chip starts to discharge the battery port under test with a constant current of 2mA. When the capacity of the battery under test is emptied, the LED light of the constant current driver chip will go out. The discharge time of the battery under test can also be determined by the time when the LED light of the constant current driver chip lights up, and then the discharge capacity of the battery under test can be calculated using the method of C=I·Δt. In this way, the discharge time and discharge capacity of the battery under test can be tested simply and directly, eliminating many cumbersome processing steps and saving equipment.
[0035] As an optional example, the constant current circuit further includes:
[0036] A first diode, a second diode and a transient suppression diode, the first end of the first diode is connected to the sixth end of the constant current drive chip, the second end of the first diode is connected to the seventh end of the constant current drive chip, the first end of the second diode is respectively connected to the third end of the constant current drive chip and the fourth end of the constant current drive chip, the second end of the second diode is connected to the first end of the operational amplifier circuit, the first end of the transient suppression diode is respectively connected to the third end of the constant current drive chip and the fourth end of the constant current drive chip, and the second end of the transient suppression diode is connected to ground.
[0037] Optionally, in this embodiment, Figure 2 As shown in the circuit connection diagram, the constant current circuit also includes a first diode D1, a second diode D2 and a transient suppression diode TVS. Specifically, the first end of the first diode D1 is connected to the sixth end Q of the constant current drive chip, the second end of the first diode D1 is connected to the seventh end REF of the constant current drive chip, the first end of the second diode D2 is respectively connected to the third end I of the constant current drive chip and the fourth end PWN of the constant current drive chip, the second end of the second diode D2 is connected to the first end of the operational amplifier circuit, the first end of the transient suppression diode TVS is respectively connected to the third end I of the constant current drive chip and the fourth end PWN of the constant current drive chip, and the second end of the transient suppression diode TVS is connected to the ground GND.
[0038] As an optional example, the constant current circuit further includes:
[0039] A first resistor, wherein a first end of the first resistor is respectively connected to the seventh end of the constant current driving chip and the second end of the first diode, and a second end of the first resistor is connected to the ground;
[0040] Optionally, in this embodiment, if Figure 2 As shown in the circuit connection diagram, the constant current circuit also includes a first resistor Ref. Specifically, the first end of the first resistor Ref is connected to the seventh end of the constant current driver chip and the second end of the first diode D1, respectively, and the second end of the first resistor Ref is connected to the ground. The constant current driver chip integrates a switch tube and a constant current control circuit, and can control the output current by adjusting the resistance value of the external resistor first resistor Ref to achieve constant current drive of the LED. For example, the constant current driver chip defines the output voltage VRefmax=0.185V, the output current I=2mA, and the resistance value of the first resistor Ref Ref=92.5Ω can be obtained by calculating V=IR, thereby achieving constant current control.
[0041] As an optional example, the resistance of the first resistor is determined by the input voltage and output current of the constant current driving chip.
[0042] Optionally, in this embodiment, the constant current driver chip integrates a switch tube and a constant current control circuit, and can control the output current by adjusting the resistance value of the external first resistor Ref to achieve constant current driving of the LED. For example, the constant current driver chip defines the output voltage VRefmax = 0.185V, the output current I = 2mA, and the resistance value of the first resistor Ref Ref = 92.5Ω can be obtained by calculating V = IR, thereby achieving constant current control.
[0043] As an optional example, the constant current circuit further includes:
[0044] A capacitor, wherein a first end of the capacitor is connected to the eighth end of the constant current driving chip, and a second end of the capacitor is connected to the ground.
[0045] like Figure 2 As shown in the circuit connection diagram, the constant current circuit further includes a capacitor C1. Specifically, a first end of the capacitor C1 is connected to the eighth end of the constant current driving chip, and a second end of the capacitor C1 is connected to the ground GND.
[0046] As an optional example, the operational amplifier circuit includes:
[0047] An operational amplifier, a second resistor and a third resistor, the output end of the operational amplifier is respectively connected to the third end of the constant current circuit and the first end of the second resistor, the inverting input end of the operational amplifier is respectively connected to the second end of the second resistor and the first end of the third resistor, the positive input end of the operational amplifier is connected to the first end of the power supply, and the second end of the third resistor is connected to the ground.
[0048] Optionally, in this embodiment, if Figure 2The circuit connection diagram shown, the operational amplifier circuit includes an operational amplifier A1, a second resistor R2 and a third resistor R1, specifically, the output terminal VCC of the operational amplifier A1 is respectively connected to the third terminal I of the constant current drive chip and the first end of the second resistor R2, the inverting input terminal of the operational amplifier A1 is respectively connected to the second end of the second resistor R2 and the first end of the third resistor R1, and the positive input terminal of the operational amplifier A1 is connected to the power supply Vin. The first end of the second resistor R2 is respectively connected to the first end VCC of the operational amplifier A1 and the third end I of the constant current drive chip, and the second end of the second resistor R2 is respectively connected to the inverting input terminal of the operational amplifier A1 and the first end of the third resistor R1. The first end of the third resistor R1 is respectively connected to the second end of the second resistor R2 and the inverting input terminal of the operational amplifier A1, and the second end of the third resistor is connected to the ground GND.
[0049] As an optional example, an operational amplifier is used to convert a low voltage of a power supply into a high voltage and then input it into a constant current driving chip.
[0050] Optionally, in this embodiment, the operational amplifier A1 is mainly used to adjust the input voltage of the constant current driver chip so that the LED constant current circuit can work normally. For example, the operational amplifier A1 converts the 3V fixed input voltage of the power supply Vin into a 9V input voltage to the TL4242 constant current driver chip, thereby achieving constant current control.
[0051] The specific testing method of this application is described with an example:
[0052] Step 1: Select components according to requirements to achieve constant current control, and set aside a positive input terminal and a negative input terminal of a constant current circuit measuring device composed of an operational amplifier circuit, a constant current circuit, and a 555 timer, wherein the positive input terminal and the negative input terminal are connected to the constant current circuit;
[0053] Step 2: directly connect the battery under test to the positive input terminal and the negative input terminal of the measuring device;
[0054] Step 3: Turn on the power switch of the measuring device circuit, the LED light of the constant current driver chip of the constant current circuit lights up, the display screen on the front of the measuring device, that is, the 555 timer starts timing and is displayed on the display screen on the front of the measuring device, and the measuring device starts to discharge the measured battery port with a constant current of 2mA;
[0055] Step 4: When the battery capacity is empty, the LED light will go out and the 555 timer will stop timing;
[0056] Step 5: By reading the time recorded by the 555 timer on the display screen, the discharge time of the tested battery can be determined;
[0057] Step 6: Calculate the discharge capacity of the battery under test using the method of C=I·Δt.
[0058] This test method can simply and directly test the discharge time and discharge capacity of the battery under test, eliminating many tedious processing steps and saving equipment.
[0059] It should be noted that, for the above-mentioned various device embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the described order of actions, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present application.
Claims
1. A discharge capacity measuring device, characterized in that: include: A power supply, a constant current circuit, an operational amplifier circuit, a timer, a positive input terminal and a negative input terminal, wherein the positive input terminal is used to be connected to the positive electrode of a battery under test, the negative input terminal is used to be connected to the negative electrode of the battery under test, the first end of the constant current circuit is connected to the positive input terminal, the second end of the constant current circuit is connected to the negative input terminal, the third end of the constant current circuit is connected to the first end of the operational amplifier circuit, the fourth end of the constant current circuit is connected to the first end of the timer, the second end of the operational amplifier circuit is connected to the first end of the power supply, and the second end of the power supply is connected to the second end of the timer.
2. The measuring device according to claim 1, characterized in that The measuring device also includes: a power switch, a first end of the power switch is connected to the second end of the power supply, and the second end of the power switch is connected to the second end of the timer, and the timer is used to start timing when the power switch is turned on, and stop timing when the discharge of the measured battery is completed.
3. The device according to claim 2, characterized in that The constant current circuit includes: a constant current drive chip, a first end of the constant current drive chip is connected to the positive input end, a second end of the constant current drive chip is connected to the negative input end, a third end of the constant current drive chip and a fourth end of the constant current drive chip are connected to the first end of the operational amplifier circuit, and a fifth end of the constant current drive chip, a sixth end of the constant current drive chip, a seventh end of the constant current drive chip and an eighth end of the constant current drive chip are connected to ground.
4. The measuring device according to claim 3, characterized in that The constant current driving chip comprises: an LED lamp, which is used to light up when the power switch is turned on, and turn off when the discharge of the tested battery is completed.
5. The measuring device according to claim 3, characterized in that The constant current circuit also includes: a first diode, a second diode and a transient suppression diode, wherein the first end of the first diode is connected to the sixth end of the constant current drive chip, the second end of the first diode is connected to the seventh end of the constant current drive chip, the first end of the second diode is respectively connected to the third end of the constant current drive chip and the fourth end of the constant current drive chip, the second end of the second diode is connected to the first end of the operational amplifier circuit, the first end of the transient suppression diode is respectively connected to the third end of the constant current drive chip and the fourth end of the constant current drive chip, and the second end of the transient suppression diode is connected to ground.
6. The measuring device according to claim 5, characterized in that The constant current circuit further includes: a first resistor, a first end of the first resistor is respectively connected to the seventh end of the constant current driving chip and the second end of the first diode, and a second end of the first resistor is connected to the ground.
7. The measuring device according to claim 6, characterized in that The resistance value of the first resistor is determined by the input voltage and output current of the constant current driving chip.
8. The measuring device according to claim 3, characterized in that The constant current circuit further includes: a capacitor, a first end of the capacitor is connected to the eighth end of the constant current driving chip, and a second end of the capacitor is connected to the ground.
9. The measuring device according to claim 1, characterized in that The operational amplifier circuit includes: an operational amplifier, a second resistor and a third resistor, the output end of the operational amplifier is respectively connected to the third end of the constant current circuit and the first end of the second resistor, the inverting input end of the operational amplifier is respectively connected to the second end of the second resistor and the first end of the third resistor, the positive input end of the operational amplifier is connected to the first end of the power supply, and the second end of the third resistor is connected to the ground.
10. The measuring device according to claim 9, characterized in that The operational amplifier is used to convert the low voltage of the power supply into a high voltage and then input it into the constant current drive chip.