Grounding resistance measuring system

Abstract

The utility model provides a ground resistance measuring system, which belongs to the technical field of ground resistance measurement, and comprises a metal table board, the metal table board is connected with a ground terminal through a ground resistor, and the metal table board is interfered to generate alternating current on the ground resistor; the input end of the signal amplification module is connected with the metal table board; the signal sampling and processing module is respectively connected with the output end of the signal amplification module, the alarm module and the display module; and the power supply module is respectively connected with the metal table board, the signal amplification module and the signal sampling processing module. The beneficial effects are that through the integration of the metal table top, the signal amplification module, the sampling processing module, the power supply module and the alarm display module, real-time and automatic determination, display and abnormity alarm of the grounding resistance of the metal table top on a production site are realized in interference environments of static ion eliminating wind, an electric field and the like without stopping production and closing an interference source for point inspection; therefore, continuous and stable operation of the production line is ensured.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of grounding resistance measurement, especially relates to a grounding resistance measurement system. BACKGROUND

[0002] Grounding resistance is the resistance generated when the grounding point of a circuit or device is connected to the ground. Its main function is to protect the circuit and device from electromagnetic interference and electrostatic discharge, and to ensure that the current can flow into the ground through the grounding system when a short circuit or lightning strike occurs, thereby protecting the safety of personnel and equipment.

[0003] In the prior art, a digital multimeter is usually used to measure the grounding resistance. When there is ionizing air blowing to the metal platform and electric field interference in the production site, the metal platform will collect alternating positive and negative ions in the ionizing air and be affected by the electric field interference, generating alternating current on the grounding resistance, which in turn superimposes the measurement sampling current applied by the digital multimeter during measurement, resulting in abnormal measurement values and failing to accurately reflect the actual grounding resistance value.

[0004] To address this problem, the current practice is usually to use periodic inspection to measure. However, the point detection method needs to be measured when the line is stopped and the ionizing air and other interference sources are turned off, which will interfere with the normal production process, reduce production efficiency, increase the complexity and cost of measurement operation. Moreover, the existing measurement method lacks visualization and alarm functions, and cannot timely and intuitively find problems and take countermeasures. UTILITY MODEL CONTENT

[0005] To solve the above technical problems, the utility model provides a grounding resistance measurement system.

[0006] The technical problem solved by the utility model can be realized by the following technical solutions:

[0007] A grounding resistance measurement system, comprising:

[0008] A metal platform connected to the ground through a grounding resistance, the metal platform generates alternating current on the grounding resistance under interference;

[0009] A signal amplification module connected to the metal platform;

[0010] A signal sampling processing module connected to the output of the signal amplification module, an alarm module and a display module;

[0011] A power module connected to the metal platform, the signal amplification module and the signal sampling processing module.

[0012] Preferably, the area of the metal platform is 2-3 square meters.

[0013] Preferably, the interference is periodic symmetric alternating interference.

[0014] Preferably, the frequency of the interference is 50 Hz.

[0015] Preferably, the signal amplification module comprises:

[0016] an operational amplifier, a non-inverting input terminal of the operational amplifier being connected to the metal platform through a first resistor, an inverting input terminal of the operational amplifier being electrically connected to an output terminal of the operational amplifier, the output terminal of the operational amplifier being connected to the signal sampling processing module;

[0017] a second resistor, connected between the non-inverting input terminal of the operational amplifier and a power supply terminal;

[0018] a first capacitor, connected between the non-inverting input terminal of the operational amplifier and a ground terminal.

[0019] Preferably, the resistance value of the first resistor is an order of magnitude multiple of the resistance value of the ground resistor.

[0020] The resistance value of the second resistor is an order of magnitude multiple of the resistance value of the ground resistor.

[0021] Preferably, the resistance value of the ground resistor is 1 megaohm.

[0022] The resistance value of the first resistor is greater than or equal to 10 megaohm.

[0023] The resistance value of the second resistor is greater than or equal to 10 megaohm.

[0024] Preferably, the signal sampling processing module comprises:

[0025] an analog-to-digital conversion sampling unit, an input terminal of the analog-to-digital conversion sampling unit being connected to an output terminal of the signal amplification module;

[0026] an average calculation unit, an input terminal of the average calculation unit being connected to an output terminal of the analog-to-digital conversion sampling unit;

[0027] a resistance conversion unit, an input terminal of the resistance conversion unit being connected to an output terminal of the average calculation unit.

[0028] Preferably, the sampling period of the signal sampling processing module is an integer multiple of the period of the interference.

[0029] Preferably, the alarm module comprises: a double-color indicator light, the double-color indicator light being used to display a first color in a first mode and a second color in a second mode.

[0030] The utility model discloses technical scheme's advantage or beneficial effect lies in:

[0031] The utility model discloses through integration metal platform, signal amplification, sampling processing, power and alarm display module, realized in the interference environment such as static ion wind and electric field, to the production site metal platform ground resistance, real -time, automatic determination, display and abnormal alarm, need not stop production and close interference source and carry out point inspection to ensure the continuous stable operation of production line, and effectively promote the intellectualization and efficiency of static protection management. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 For the preferred embodiment of the utility model, the structure block diagram of the ground resistance measurement system;

[0033] Figure 2 For the preferred embodiment of the utility model, the voltage waveform schematic diagram at the ground resistance;

[0034] Figure 3 For the preferred embodiment of the utility model, the voltage waveform schematic diagram of filtering and sampling. DETAILED DESCRIPTION

[0035] The technical scheme in the embodiments of the utility model will be described clearly and completely below in conjunction with the drawings of the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the utility model.

[0036] It should be noted that the embodiments in the utility model and the features in the embodiments can be combined with each other without conflict.

[0037] The utility model will be further described below in conjunction with the drawings and specific embodiments, but not as the limitation of the utility model.

[0038] Referring to Figure 1 , in the preferred embodiment of the utility model, based on the above-mentioned problems existing in the prior art, a ground resistance measurement system is provided, comprising:

[0039] Metal platform 1, metal platform 1 is connected to the ground end through ground resistance R0, and the metal platform 1 generates alternating current on the ground resistance R0 under interference;

[0040] Signal amplification module 3, the input end of signal amplification module 3 is connected to metal platform 1;

[0041] Signal sampling processing module 4 is respectively connected to the output end of signal amplification module 3, alarm module 5 and display module 6;

[0042] A power module 7 is connected to the metal platform 1, the signal amplification module 3 and the signal sampling processing module 4 respectively.

[0043] Specifically, in the embodiment, the metal platform 1 is connected to the ground end through a 1-mega-ohm grounding resistor R0. In actual application, the metal platform 1 will be disturbed by the 50-Hz alternating ionic wind generated by the static-eliminating ionic wind rod above and the interference source 2 such as the surrounding electric field, and the alternating voltage and current will be induced on the grounding resistor R0.

[0044] In order to effectively capture and process these weak signals, the system is equipped with a signal amplification module 3, the input end of which is connected to the metal platform 1, for amplifying the induced alternating current signal. Subsequently, the amplified signal is sent to the signal sampling processing module 4, which is responsible for sampling, processing and analyzing the signal, and once the abnormality of the grounding resistor R0 is detected, the alarm module 5 is triggered to issue a warning, and the current resistance value of the grounding resistor R0 is displayed in real time through the display module 6.

[0045] The power module 7 provides stable power support for the entire system, and the power module 7 is connected to the metal platform 1, the signal amplification module 3 and the signal sampling processing module 4 respectively, to ensure that each module can operate normally and efficiently.

[0046] The utility model can realize real-time, automatic measurement, display and abnormal alarm of the grounding resistor R0 of the metal platform 1 in the interference environment of static-eliminating ionic wind and electric field, without stopping production to close the interference source for inspection, thereby ensuring the continuous and stable operation of the production line and effectively improving the intelligence and efficiency of static protection management.

[0047] As a preferred embodiment, the area of the metal platform is 2-3 square meters.

[0048] Specifically, in the embodiment, a large metal platform with an area of 2-3 square meters is used as a test platform, and the metal platform can be made of stainless steel, such as a common stainless steel workbench, to ensure sufficient test area and facilitate various grounding resistance measurement operations.

[0049] As a preferred embodiment, the interference is periodic and symmetric alternating interference.

[0050] As a preferred embodiment, the frequency of the interference is 50Hz.

[0051] Specifically, in actual application, it is found that the 50-Hz alternating ionic wind generated by the static-eliminating ionic wind rod above the metal platform 1 and the interference generated by the interference source 2 such as the surrounding electric field is periodic and symmetric alternating interference, and the frequency of the interference is 50Hz.

[0052] For periodic symmetrical alternating interference, such as Figure 2 As shown in the figure, curve S1 represents the interference voltage signal applied by the interference source 2 on the grounding resistor R0, which is characterized in that: since the frequency is 50Hz, the arithmetic mean of the interference signal is 0.

[0053] Curve S2 represents the voltage signal applied on the grounding resistor R0 when measured by the digital multimeter.

[0054] Curve S3 represents the result of the addition of the measurement voltage signal S2 and the interference voltage signal S1 when measured by the digital multimeter.

[0055] As a preferred embodiment, wherein the signal amplification module 3 comprises:

[0056] The non-inverting input terminal of the operational amplifier 31 is electrically connected to the metal platform 1 through the first resistor R1, and the inverting input terminal and the output terminal of the operational amplifier 31 are electrically connected, and the output terminal of the operational amplifier 31 is connected to the signal sampling processing module 4;

[0057] The second resistor R2 is connected between the non-inverting input terminal of the operational amplifier 31 and the power supply terminal;

[0058] The first capacitor C1 is connected between the non-inverting input terminal of the operational amplifier 31 and the ground terminal.

[0059] Specifically, the signal amplification module 3 mainly comprises the operational amplifier 31, the second resistor R2 and the first capacitor C1. The non-inverting input terminal of the operational amplifier 31 is electrically connected to the metal platform 1 through the first resistor R1, for receiving the signal from the metal platform 1, and the inverting input terminal and the output terminal thereof are electrically connected to form a feedback loop. The output terminal transmits the amplified signal to the signal sampling processing module 4.

[0060] The second resistor R2 is connected to the 5V power supply terminal, which provides the necessary bias current for the operational amplifier 31 and ensures its normal work.

[0061] In this embodiment, the operational amplifier 31 adopts a single power supply mode. Under the interference of ion wind power field and the like, the resistance value of the grounding resistor may be affected and always jumps and changes, or even appears a negative resistance value, and the operational amplifier with single power supply cannot measure the negative voltage. In the embodiment of the utility model,

[0062] In the presence of ion wind power plant and other interference, by connecting the first capacitor C1 between the positive input terminal and the ground terminal of the operational amplifier 31, the input signal is filtered, the amplitude of the alternating current signal is reduced, and the negative value in the measurement process is avoided. At the same time, the operational amplifier 31 also plays a role in voltage following and improving input resistance, replacing the low input resistance of the single-chip microcomputer AD port with its high input resistance, thereby ensuring the accuracy of the measurement.

[0063] As shown in Figure 3 The curve S4 represents the effect of adding the first capacitor C11: filtering the interference signal of the alternating current characteristic through the first capacitor C1 can significantly reduce its amplitude, ensuring that all measured signals are positive, thereby meeting the requirements of the single power supply operational amplifier and the signal sampling processing module 4 of the MCU, which cannot measure negative values. The addition of the first capacitor C1 not only improves the stability and accuracy of the signal, but also ensures the reliable operation of the entire system in complex environments.

[0064] Specifically, by selecting a suitable capacitance value, such as C1 = 0.1uf, and combining the resistance value of the first resistor R1, the time constant τ = RC = 10000Ω*0.1*10E-6 = 0.01s can be calculated. The time constant ensures that the response speed of the circuit to the alternating current interference signal is fast enough to effectively reduce the amplitude of the alternating current signal and avoid negative values.

[0065] As a preferred embodiment, the resistance value of the first resistor R1 is an order of magnitude multiple of the resistance value of the ground resistor R0.

[0066] The resistance value of the second resistor R2 is an order of magnitude multiple of the resistance value of the ground resistor R0.

[0067] Specifically, the order of magnitude refers to the scale or level of the quantity, and the order of magnitude is generally based on 10 (i.e. 10 raised to the power of how many times). That is, the resistance value of the first resistor R1 and the second resistor R2 is an order of magnitude of the resistance value of the ground resistor R0.

[0068] As a preferred embodiment, the resistance value of the ground resistor R0 is 1 megaohm.

[0069] The resistance value of the first resistor R1 is greater than or equal to 10 megaohm.

[0070] The resistance value of the second resistor R2 is greater than or equal to 10 megaohm.

[0071] Specifically, in order to meet the requirement that the measurement system does not affect the original ESD 1M ohm discharge system, the operational amplifier 31 is used to improve the input impedance in this embodiment. The first resistor R1 and the second resistor R2 use resistors greater than 10 megaohm, which basically do not destroy the original ground resistor R0 electrostatic discharge (ESD) conditions.

[0072] The first resistance R1 is equivalent to the input resistance of the measuring system, and after being connected in parallel with the 1MΩ grounding resistance R0 for electrostatic discharge (ESD), the equivalent resistance is 0.91MΩ, which has little effect on the 1MΩ condition of the measured ESD. Therefore, when selecting the resistance value of R1, the resistance value of the first resistance R1 is generally greater than 10MΩ, that is, the input impedance of the operational amplifier is as high as 1GΩ or more, which can ensure that the original ESD discharge system is not affected during the measurement.

[0073] At the same time, the first resistance R1 and the second resistance R2 also provide a measuring voltage and current for the grounding resistance R0, ensuring the accuracy and reliability of the measurement process.

[0074] As a preferred embodiment, the signal sampling processing module 4 comprises:

[0075] an analog-to-digital conversion sampling unit, the input end of the analog-to-digital conversion sampling unit being connected to the output end of the signal amplification module, for converting the analog signal into a digital signal;

[0076] an average calculation unit, the input end of the average calculation unit being connected to the output end of the analog-to-digital conversion sampling unit, for performing arithmetic average processing on the sampled digital signal to remove the alternating current interference signal;

[0077] a resistance conversion unit, the input end of the resistance conversion unit being connected to the output end of the average calculation unit, for converting the resistance value according to the signal value after the average processing.

[0078] Specifically, the signal sampling processing module has the functions of analog-to-digital conversion sampling, average calculation and resistance conversion. In this embodiment, the functions of the signal sampling processing module can be realized by a microcontroller unit (MCU). The MCU has the functions of analog-to-digital conversion sampling, average calculation and resistance conversion, and can efficiently complete the signal processing.

[0079] The AD port of the MCU has an input resistance of about several hundred KΩ (KΩ), which is not suitable for directly measuring the resistance of the order of MΩ (MΩ), and it is also not allowed to be directly connected to the electrostatic discharge (ESD) system, because this may weaken the original ESD discharge 1MΩ condition. If the AD port of the single-chip microcomputer is directly connected to the 1MΩ grounding resistance R0, it is equivalent to connecting a 500KΩ resistance in parallel with the 1MΩ resistance. Assuming that the input resistance of the AD port is 500KΩ, the equivalent resistance of the 1MΩ grounding resistance R0 connected in parallel with the 500KΩ resistance will be reduced to about 333KΩ, which obviously destroys the original 1MΩ ESD discharge condition.

[0080] Therefore, the embodiment of the utility model in series links an operational amplifier 31 in front of the AD port of MCU. The operational amplifier has very high input impedance, can choose the MOS technology operational amplifier of input impedance above 1GΩ, guarantees that the access of operational amplifier will not affect the voltage division relationship of the first resistance R1 and the second resistance R2. When the input impedance of operational amplifier 31 is 1GΩ, and the resistance value of the second resistance R2 is 10MΩ, the equivalent resistance of parallel connection is 9.901MΩ, still close to 10MΩ, the influence to the original circuit is infinitesimal.

[0081] It should be noted that the utility model aims at realizing real-time full-time automatic real-time ground resistance measurement display and abnormal alarm to meet the actual application demand, the utility model belongs to the industrial innovation by the way of combination using the data processing capacity and hardware control capacity of microprocessor, the utility model does not involve any innovation of software, the transmission mode or control mode between the analog-digital conversion sampling unit, average calculation unit and resistance conversion unit, although it cannot be separated from software code, but these software codes belong to prior art, the technical personnel in the art only need to cut or transplant the existing code to the utility model, of course, can also be according to the product technical document to write, therefore, the utility model wants to protect is the hardware connection relationship, and does not involve the innovation of software.

[0082] As a preferred embodiment, the sampling period of the signal sampling processing module 4 is an integer multiple of the period of the interference.

[0083] In order to obtain accurate sampling value, the sampling period is set as an integer multiple of the period of the interference signal. Specifically, since the interference signal has a 50HZ alternating symmetry characteristic, the embodiment uniformly and continuously samples and AD converts an integer number of complete period sinusoidal signals at high density to ensure that there are enough sampling points in each sinusoidal period, thereby more accurately reflecting the change of the signal. After sampling is completed, the collected data is arithmetically averaged to obtain the AD value of the direct current component signal sampling voltage after removing the alternating interference signal, and the resistance value of the grounding resistance is converted based on this value. The error of the value is about 1% to 2%, which has high accuracy.

[0084] As shown in Figure 3 S5 represents uniformly interval sampling and AD conversion of an integer number of complete periods to obtain the average value of the required alternating interference voltage AD value. In specific operation, the sampling time interval of the embodiment is set to 5us to 100us, and no less than 200 points are sampled in each sinusoidal period. At the same time, the number of complete sampling periods can be selected as 1 to 20. The utility model samples 5 complete periods, the sampling time interval is 5us, and the number of sampling points is 20ms / 5us=40000 points, for example, to improve the precision and stability of measurement.

[0085] For the control of the complete cycle, timing control or Max value control can be adopted. Timing control is to sample according to the set time interval, while Max value control is to start the sampling process after detecting the maximum value of the signal, and to stop sampling until the 6th maximum value is detected.

[0086] Specifically, in the average calculation unit, the calculation formula is:

[0087] DATAad = (AD0 + AD1 +... ADn) / n

[0088] Wherein, n is the number of samples, ADn is the sampling value of the nth time, and DATAad is the average value of n sampling values.

[0089] In the resistance conversion unit, the resistance conversion formula is:

[0090] Vad = DATAad / 1024 * 5V

[0091] Wherein, Vad is the analog-to-digital conversion value; the AD converter is 10 bits, and the 10-bit AD converter has a resolution of 1 / 1024. The power module, i.e. the voltage provided by the power supply end, is 5V.

[0092] The ground resistance Resd is calculated according to the following formula:

[0093] 10M / (10M + Resd + 10M) * 5V = DATAad / 1024 * 5V

[0094] It is derived that:

[0095] Resd = (1024 * 11 - 20 * DATAad) / DATAad

[0096] After the resistance value of the ground resistance is converted, the real-time resistance value is displayed by the OLED, and the real-time resistance value is compared with the set upper and lower limit values, and the warning is given by the indicator light.

[0097] As a preferred embodiment, wherein the warning module 5 comprises: a double-color indicator light, the double-color indicator light is used to display a first color in a first mode and a second color in a second mode.

[0098] In this embodiment, the first mode is that the resistance value of the ground resistance is within the specification, i.e. the resistance value of the ground resistance is within the set upper and lower limit range.

[0099] In this embodiment, the second mode is that the resistance value of the ground resistance is out of the specification, i.e. the resistance value of the ground resistance exceeds the set upper and lower limit range.

[0100] In this embodiment, the upper limit value and the lower limit value of the upper and lower limit range can be set by the user.

[0101] In the embodiment, the double-color indicator light is preferably a red-green double-color LED indicator light, which displays a red light to give an alarm when the resistance value of the grounding resistor exceeds the set upper and lower limit ranges, and displays a green light when the resistance value does not exceed the ranges.

[0102] Further, two indicator lights can be provided, which display different colors, preferably one displays red and the other displays green, to replace the single double-color indicator light.

[0103] Further, in order to enhance the alarm function of the system, the alarm module 5 can further include a buzzer. When the system detects that the resistance value of the grounding resistor exceeds the set upper and lower limit ranges, the red light is on, and the buzzer emits a sound alarm to give a sound-light dual alarm.

[0104] Further, the display module 6 adopts an IIC interface OLED screen to display the resistance value and the alarm signal in real time.

[0105] Further, the power module 7 adopts a USB 5V adapter as the power supply of the measurement system. The USB line is the power line (5V+, 5V-) of the measurement system, wherein the 5V- end is connected with the ground of the power supply extension board.

[0106] The above technical scheme has the advantages or beneficial effects that: the utility model integrates a metal table top, signal amplification, sampling processing, power supply and alarm display module, realizes real-time, automatic measurement, display and abnormal alarm of the grounding resistor of the metal table top in the interference environment such as electrostatic ion wind and electric field, does not need to stop production, closes the interference source to carry out point inspection, thereby ensuring the continuous and stable operation of the production line, and effectively improving the intelligentization and efficiency of electrostatic protection management.

[0107] The above is only the preferred embodiment of the utility model, and does not limit the implementation and protection scope of the utility model. For those skilled in the art, it should be realized that any equivalent replacement and obvious change made according to the content of the specification and drawings should be included in the protection scope of the utility model.

Claims

1. A ground resistance measuring system characterized by, The utility model relates to a kind of signal sampling device, including: Metal platform, the ground end is connected by ground resistance connection, alternating current is generated on the ground resistance by interference on the metal platform; Signal amplification module, the input of the signal amplification module is connected to the metal platform; Signal sampling processing module is connected to the output of the signal amplification module, alarm module and display module respectively; Power module is connected to the metal platform, the signal amplification module and the signal sampling processing module respectively.

2. The ground resistance measurement system of claim 1, wherein, The area of the metal platform is 2-3 square meters.

3. The ground resistance measurement system of claim 1, wherein, The interference is periodic symmetric alternating interference.

4. The ground resistance measurement system of claim 1, wherein, The frequency of the interference is 50Hz.

5. The ground resistance measurement system of claim 1, wherein, The signal amplification module includes: Operational amplifier, the positive phase input of the operational amplifier is connected to the metal platform by first resistance, the output between the inverting input of the operational amplifier and is electrically connected, the output of the operational amplifier is connected to the signal sampling processing module; Second resistance is connected between the positive phase input of the operational amplifier and power supply end; First capacitor is connected between the positive phase input of the operational amplifier and ground terminal.

6. The ground resistance measurement system of claim 5, wherein, The resistance value of the first resistance is the order of magnitude multiple of the resistance value of the ground resistance; The resistance value of the second resistance is the order of magnitude multiple of the resistance value of the ground resistance.

7. The ground resistance measurement system of claim 5, wherein, The resistance value of the ground resistance is 1MΩ; The resistance value of the first resistance is greater than or equal to 10MΩ; The resistance value of the second resistance is greater than or equal to 10MΩ.

8. The ground resistance measurement system of claim 1, wherein, The signal sampling processing module includes: Analog-digital conversion sampling unit, the input of the analog-digital conversion sampling unit is connected to the output of the signal amplification module; Average calculation unit, the input of the average calculation unit is connected to the output of the analog-digital conversion sampling unit; Resistance conversion unit, the input of the resistance conversion unit is connected to the output of the average calculation unit.

9. The ground resistance measurement system of claim 1, wherein, The sampling period of the signal sampling processing module is the integer multiple of the period of the interference.

10. The ground resistance measurement system of claim 1, wherein, The alarm module includes: double-color indicating lamp, the double-color indicating lamp is used to display first color in first mode, and display second color in second mode.

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