Safety test instrument

Abstract

The utility model discloses a safety test instrument, which relates to the technical field of test and comprises a main body shell, a test interface group, a drain voltage and ground resistance test circuit and a leakage current test circuit. The leakage voltage and grounding resistance test circuit comprises a first isolation transformer, a voltage adjusting knob, a resistance adjusting knob, a first control switch and a second control switch, and is used for detecting leakage voltage and grounding resistance values. The leakage current test circuit comprises a power supply selection switch, a second isolation transformer, a measuring range selection switch and a current adjusting knob and is used for detecting the magnitude of current; the voltage adjusting knob, the resistance adjusting knob, the current adjusting knob, the first control switch, the second control switch, the voltage display meter, the current display meter, the resistance display meter and the range selection switch are all arranged on the main body shell. The utility model solves the problem that a test instrument in the prior art is difficult to be compatible with a plurality of instruments and is inconvenient to use.

Description

Technical Field

[0001] This utility model relates to the field of testing technology, and in particular to a safety testing instrument. Background Technology

[0002] To ensure that the power distribution system meets national safety standards, key safety indicators such as grounding resistance, leakage voltage, and leakage current must be tested regularly.

[0003] Currently, existing technologies typically employ separate testing instruments to test the aforementioned safety indicators, using grounding resistance testers, leakage voltage testers, and leakage current testers for individual measurements. Testing personnel must carry multiple instruments and repeatedly connect and switch equipment for different test items, resulting in cumbersome and time-consuming operations. This makes it difficult to meet the rapid testing needs of field or mobile environments, and the reliability of the test results is questionable. Utility Model Content

[0004] The main purpose of this utility model is to propose a safety testing instrument, which aims to solve the problem that existing testing instruments are difficult to be compatible with multiple instruments, resulting in inconvenience in use.

[0005] To achieve the above objectives, the safety testing instrument proposed in this utility model includes a main housing, a test interface group disposed on the main housing, a leakage voltage and grounding resistance test circuit disposed inside the main housing, and a leakage current test circuit.

[0006] The test interface group includes at least a first interface pair for connecting the device under test and a second interface pair for connecting an external current monitoring device;

[0007] The leakage voltage and grounding resistance test circuit includes: a first isolation transformer, a voltage adjustment knob, a resistance adjustment knob, a first control switch, and a second control switch;

[0008] The second control switch has a common terminal, a first selection terminal, and a second selection terminal;

[0009] The output terminal of the first isolation transformer is connected to the common terminal of the second control switch;

[0010] The first selection terminal is connected to the input terminal of the voltage adjustment knob, and the output terminal of the voltage adjustment knob is connected to a voltage display meter;

[0011] The second selection terminal is connected to the input terminal of the first control switch; the first control switch is configured to selectively switch its input terminal to the input terminal of the resistance adjustment knob or the first interface pair, and the output terminal of the first control switch is connected to a resistance display meter;

[0012] The leakage current test circuit includes: a power selection switch, a second isolation transformer, a range selection switch, and a current adjustment knob.

[0013] The input terminal of the power selection switch is used to selectively connect to one phase of a single-phase AC power supply or a three-phase AC power supply, and the output terminal is connected to the input terminal of the second isolation transformer.

[0014] The output terminal of the second isolation transformer, the range selection switch, and the current adjustment knob are connected in series in sequence, and the output terminal of the current adjustment knob is connected to a current display meter.

[0015] The voltage adjustment knob, resistance adjustment knob, current adjustment knob, first control switch, second control switch, voltage display meter, current display meter, resistance display meter, and range selection switch are all located on the main body shell.

[0016] In one embodiment, the main housing includes a front panel and a rear panel. The test interface group, voltage adjustment knob, resistance adjustment knob, current adjustment knob, first control switch, second control switch, and range selection switch are disposed on the front panel; the power selection switch, single-phase power input, and three-phase power input are disposed on the rear panel.

[0017] In one implementation, the second interface is configured to either connect an external ammeter or be in a short-circuited state.

[0018] In one embodiment, a cooling fan is also provided inside the main housing, and the airflow path of the cooling fan passes through the area where the leakage current test circuit is located.

[0019] In one embodiment, an air inlet is provided on the rear panel, the position of which corresponds to the air intake side of the cooling fan; an air outlet is provided on the left and / or right side of the main housing, the air outlet corresponding to the air duct of the cooling fan.

[0020] In one embodiment, the resistance adjustment knob is used to adjust the grounding resistance value in the range of 0-100kΩ, the voltage adjustment knob is used to adjust the leakage voltage value in the range of 0-60V, and the current adjustment knob is used to adjust the leakage current value in the range of 5mA-500mA. The adjustment range of the current adjustment knob is set by the range selection switch.

[0021] In one embodiment, the range selection switch is a mechanical switch with multiple fixed positions, including at least a first position, a second position, and a third position, corresponding to leakage current adjustment ranges of less than 15mA, 10mA-60mA, and 40mA-500mA, respectively.

[0022] In one embodiment, the main body housing is further provided with an indicator at the lower end of the resistance adjustment knob, voltage adjustment knob and current adjustment knob, the indicator being used to indicate the adjustment direction of each knob.

[0023] In one embodiment, a handle is provided on the main body shell.

[0024] In one embodiment, two fixing seats are disposed opposite each other on the top of the main body shell, and the two ends of the handle are respectively fixedly disposed in the fixing seats, and the middle part of the handle is arc-shaped with an opening facing the main body shell.

[0025] The technical solution of this utility model is to set up a test instrument that integrates grounding resistance detection, leakage voltage detection and leakage current detection functions, thereby integrating the three major safety test functions into a single instrument, thus solving the problems of complicated wiring, inconvenient equipment carrying and low test efficiency caused by the incompatibility of using multiple separate instruments.

[0026] By setting up coordinated control of various adjustment knobs and range selection switches, a continuous, stable, and precisely adjustable leakage current simulation signal is generated within the range, meeting the needs of small current testing and large range coverage, and ensuring the accuracy and reliability of test results. Attached Figure Description

[0027] 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 the structures shown in these drawings without creative effort.

[0028] Figure 1 A schematic diagram of the structure of the safety testing instrument provided by this utility model;

[0029] Figure 2 for Figure 1 A schematic diagram of the back structure;

[0030] Figure 3 for Figure 1 A schematic diagram of the top structure in the diagram;

[0031] Figure 4 for Figure 1 A schematic diagram of the side structure in the middle;

[0032] Figure 5 Schematic diagram of leakage voltage and grounding resistance detection principle of the safety testing instrument provided by this utility model;

[0033] Figure 6The leakage current detection principle diagram of the safety testing instrument provided by this utility model.

[0034] Explanation of icon numbers:

[0035] 100. Main body casing; 101. Handle; 102. Air inlet; 103. Air outlet; 200. Power input interface; 300. First interface pair; 301. Second interface pair; 401. First control switch; 402. Second control switch; 501. Resistance adjustment knob; 502. Voltage adjustment knob; 503. Current adjustment knob; 504. First isolation transformer; 505. Second isolation transformer; 601. Power selection switch; 602. Three-phase power interface; 603. Single-phase power interface; 700. Range selection switch; 801. Current display meter; 802. Voltage display meter; 803. Resistance display meter.

[0036] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0037] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.

[0038] It should be noted that if the embodiments of this utility model involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0039] Furthermore, if the embodiments of this utility model involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0040] This utility model proposes a safety testing instrument.

[0041] Please see Figure 1 and Figure 2 In one embodiment of the present invention, the safety test instrument includes a main housing 100, a test interface group, a leakage voltage and grounding resistance test circuit, and a leakage current test circuit.

[0042] The leakage voltage and grounding resistance test circuit and the leakage current test circuit are disposed inside the main body housing 100; the test interface group is disposed on the main body housing 100, and the test interface group includes at least a first interface pair 300 for connecting the device under test and a second interface pair 301 for connecting an external current monitoring device;

[0043] The leakage voltage and grounding resistance test circuit includes: a first isolation transformer 504, a voltage adjustment knob 502, a resistance adjustment knob 501, a first control switch 401, and a second control switch 402.

[0044] The input terminal of the first isolation transformer 504 is connected to a single-phase AC power supply, and the output terminal is connected to the input terminal of the second control switch 402; the second control switch 402 has a common terminal, a first selection terminal, and a second selection terminal.

[0045] The output terminal of the first isolation transformer 504 is connected to the common terminal of the second control switch 402; the first selection terminal is connected to the input terminal of the voltage adjustment knob 502; the second selection terminal is connected to the input terminal of the first control switch 401; the first control switch 401 is configured to selectively switch its input terminal to the input terminal of the resistance adjustment knob 501 or the first interface pair 300.

[0046] It is understood that the leakage voltage and grounding resistance test circuit of this application includes at least a leakage voltage test circuit and a grounding resistance test circuit;

[0047] In this application, the second control switch 402 is a dual-position switch with a leakage voltage position and a grounding resistance position. When the second control switch 402 is set to the leakage voltage position, the adjustment terminal of the voltage adjustment knob 502 is connected to the leakage voltage output circuit of the second control switch 402, and the output terminal of the voltage adjustment knob 502 is connected to the voltage display meter 802. When the second control switch 402 is set to the grounding resistance position, the adjustment terminal of the resistance adjustment knob 501 is connected to the grounding resistance output circuit of the second control switch 402, and can be selectively connected to the resistance adjustment knob 501 or the first interface pair 300 by switching the first control switch 401.

[0048] The leakage current testing circuit includes: a power selection switch 601, a second isolation transformer 505, a range selection switch 700, and a current adjustment knob 503; the input terminal of the power selection switch 601 is used to selectively connect to one phase of a single-phase AC power supply or a three-phase AC power supply, and the output terminal is connected to the input terminal of the second isolation transformer 505; the output terminal of the second isolation transformer 505, the range selection switch 700, and the current adjustment knob 503 are connected in series, and the output terminal of the current adjustment knob 503 is connected to the current display meter 801;

[0049] The voltage adjustment knob 502, resistance adjustment knob 501, current adjustment knob 503, first control switch 401, second control switch 402, voltage display meter 802, current display meter 801, resistance display meter 803, and range selection switch 700 are all located on the main housing 100.

[0050] It is understood that the leakage voltage and grounding resistance test circuit and the leakage current test circuit are integrated functional circuits on the printed circuit board (PCB) and housed inside the main body housing 100. They are used to perform three safety test functions: grounding resistance, leakage voltage and leakage current, and receive control signals from the operation panel and output drive signals to each display meter.

[0051] It is understood that the power supply of this application is provided through a power input interface 200 provided on the main housing 100; optionally, the power input interface 200 is provided on the side or rear of the main housing 100, and may be an AC power socket, which is directly electrically connected to the power input terminal of the test circuit to provide working power for the entire instrument.

[0052] In this application, the first isolation transformer 504 is used for safe isolation and voltage adaptation of the leakage voltage and grounding resistance test circuit. The first isolation transformer 504 electromagnetically isolates the higher power supply voltage on the primary side and transforms it into a lower safe voltage on the secondary side to prevent high voltage from entering the subsequent test circuit and output terminal, thus ensuring operational safety.

[0053] In this embodiment, the test interface group is centrally arranged on the front panel or side panel of the main housing 100 and electrically connected to the internal test circuit. The test interface group specifically includes: the first interface pair 300 is configured with two terminals, and in some preferred embodiments, 4mm terminals are used for connecting the external vehicle ground and the test ground; in use, it is connected to the vehicle ground of the equipment under test and the grounding point to be tested through wires respectively.

[0054] Similarly, the second interface pair 301 is located on one side of the first interface pair 300. The second interface pair 301 is electrically connected to the leakage current test circuit of the test circuit, and is used to connect an external high-precision ammeter for calibration or high-precision monitoring. If no external instrument is connected, it must be shorted with a shorting piece to ensure the continuity of the internal circuit.

[0055] In this embodiment, the voltage display meter 802, current display meter 801, and resistance display meter 803 are all embedded in the operation panel. They are pointer-type or digital instruments used to display various parameters during the testing process in real time, and their signal input terminals are electrically connected to the output terminals of the test circuit. The signal input terminal of the resistance display meter 803 is connected to the signal output or measurement terminal of the leakage voltage and grounding resistance test circuit; the signal input terminal of the voltage display meter 802 is connected to the signal output terminal of the leakage voltage and grounding resistance test circuit; and the signal input terminal of the current display meter 801 is connected to the signal output terminal of the leakage current test circuit. The three meters are used to display the corresponding test parameters in real time, independently, and synchronously. When performing any one or a combination of tests, the user can directly read the precise set value or measured value from the corresponding meter. For example, when adjusting the leakage current, the current display meter 801 displays the changing current value in real time.

[0056] In this embodiment, the first control switch 401 has a resistance measurement range, a resistance display range, and a disconnect range. The first control switch 401 is electrically connected to the leakage voltage and grounding resistance test circuit. The second control switch 402 has a leakage voltage range and a grounding resistance range, and is used to switch the first interface pair 300 to the leakage voltage test circuit or the grounding resistance test circuit.

[0057] In this embodiment, the first control switch 401 is a three-position toggle switch, and the corresponding positions are marked on the main housing 100 as resistance measurement and resistance display; the common terminal or output terminal of the first control switch 401 is electrically connected to the control and signal path of the grounding resistance test circuit; the user toggles this switch to select the working state related to the grounding resistance test, and the working states of each position include:

[0058] Resistance measurement mode: The instrument acts as a signal source and outputs an adjustable analog grounding resistance value, set by the resistance adjustment knob 501, to the outside via the first interface 300.

[0059] Resistance display mode: As a measuring instrument, the instrument measures and displays the actual grounding resistance value in the external measured circuit through the first interface.

[0060] Disconnect setting: This setting ensures a safe physical disconnect between the leakage voltage and grounding resistance test circuit and the test interface.

[0061] The second control switch 402 is a two-position toggle switch. The corresponding positions on the main housing 100 are marked with leakage voltage and grounding resistance. When the user toggles the second control switch 402 to select a test item, this essentially switches the electrical connection path between the first interface and 300. The operating states of each position include:

[0062] Leakage voltage setting: The first interface is directly connected to the leakage voltage and grounding resistance test circuit, and the instrument performs leakage voltage test.

[0063] Grounding resistance setting: Connect the first interface pair 300 to the output terminal of the first control switch 401; at this time, the resistance measurement or resistance display function of the first interface pair 300 is determined by the current setting of the first control switch 401.

[0064] Understandably, the second control switch 402 is used to make a primary selection between the two major items of voltage testing and resistance-related testing; when resistance-related testing is selected, the first control switch 401 is responsible for making a secondary selection between the two operating modes of output resistance and measurement resistance.

[0065] The leakage voltage and grounding resistance test circuit includes a first isolation transformer 504 for achieving electrical safety isolation between the input and output. The first isolation transformer 504 safely transforms the higher power supply voltage on the primary side to a lower voltage on the secondary side, suitable as a source for simulating leakage voltage; and through magnetic coupling, it transfers energy, achieving electrical isolation between the primary circuit and the secondary output circuit. This ensures that even if an abnormally high voltage occurs on the primary side, it will not be directly conducted to the output terminal of the device under test, thus protecting the safety of the operator.

[0066] The leakage current test circuit includes a second isolation transformer 505, which is used to achieve electrical safety isolation between the test power supply and the current generation circuit. The second isolation transformer 505 safely transforms the primary side single-phase or three-phase power supply voltage selected by the power selection switch 601 into a uniform low voltage suitable for Ohm's law constant current source on the secondary side; and transfers energy through magnetic coupling, realizing electrical isolation between the external test power supply network and the internal adjustable current circuit. This ensures that even if there is an abnormality or interference on the external test power supply side, it will not be directly conducted to the internal circuitry and final output of the instrument, thereby ensuring the safety of the leakage current test process. Together with the first isolation transformer 504, it forms a double safety isolation within the instrument.

[0067] It is understood that the single-phase power interface 603 is a standard two- or three-pin AC power socket used to connect a single-phase AC220V test power supply. The three-phase power interface 602 is a four-pin aviation plug used to connect a three-phase AC380V test power supply, with its pins corresponding to phase A, phase B, phase C, and the neutral line (N). In this application, the conductive terminals of both the single-phase power interface 603 and the three-phase power interface 602 are led into and connected to the input terminal of the power selection switch 601.

[0068] The power selection switch 601 is a multi-position mechanical rotary switch or toggle switch. For example, the power selection switch 601 is a mechanical rotary switch, and its multiple input terminals are respectively connected to the live wire (L) terminal of the single-phase interface and the A, B, and C phase terminals of the three-phase interface; the common output terminal of the power selection switch 601 is directly connected to the power input terminal of the leakage current test circuit.

[0069] The user-operated power selection switch 601 allows users to select one of multiple connected power sources as the excitation power for leakage current testing. The switch offers four positions: Off, Single Phase, A Phase, B Phase, and C Phase. Selecting the Single Phase position connects the power from the single-phase interface; selecting A Phase, B Phase, or C Phase connects the power from the corresponding phase of the three-phase interface. This allows a single instrument to flexibly adapt to different power environments in the field and test the leakage current protection performance of each phase.

[0070] See Figure 5In this application, the power input terminal of the leakage voltage grounding resistance detection circuit is equipped with an input protection circuit; the input protection circuit includes at least a fuse and an electromagnetic interference filter; its input terminal is connected to the single-phase AC power supply of the instrument, and its output terminal is connected to the first isolation transformer. The fuse inside the input protection circuit can quickly blow and cut off the power supply when a short circuit or severe overload occurs in the circuit, preventing the fault from spreading; the EMI filter can suppress instantaneous high voltage spikes and electromagnetic interference from the power grid, and also helps to reduce the reverse interference of the instrument's internal circuit to the power grid, improving the stability and safety of the entire test system.

[0071] See Figure 5 The principle of the leakage voltage and grounding resistance detection function of the test circuit in this application is as follows: When the power supply is connected, the single-phase AC input power is converted from the primary AC220V to the secondary AC60V through the input socket with built-in switch and fuse, and then through the first isolation transformer 504. This provides a safer AC voltage for the subsequent stages. When the grounding resistance / leakage voltage measurement selection switch is operated, the leakage voltage measurement value of the device under test from AC0V to 60V can be provided through the leakage voltage adjustment knob 502. The leakage voltage display meter 802 can display the leakage voltage value in real time. When the grounding resistance measurement is selected, the grounding resistance display / measurement selection switch needs to be used. If the grounding resistance display is to be viewed, the grounding resistance display / measurement is to be switched to the resistance display position, and the current resistance value can be displayed on the grounding resistance display meter 803. If the grounding resistance is to be tested, the grounding resistance display / measurement is to be switched to the resistance measurement position, and the grounding resistance adjustment knob 501 can provide the grounding resistance measurement value of the device under test from 0 to 100kΩ.

[0072] See Figure 6 The leakage current detection principle of the test circuit in this application is as follows: an external excitation power supply for leakage current testing is provided, which can be selected from either single-phase AC220V or three-phase AC380V. The user selects the input source through the power selection switch 601 on the operation panel. The selected power supply is then connected to an isolation transformer, which converts the higher primary input voltage AC220V to AC60V to achieve electrical safety isolation, ensuring complete isolation between the subsequent circuit and the output terminal from dangerous high voltage. The output current range is coarsely selected through the range selection switch 700 to determine the approximate range of current adjustment. Based on a resistor R circuit selected by the range selection switch 700, the user can change the effective resistance value R in that circuit by rotating the current adjustment knob 503 on the operation panel.

[0073] It should be noted that the range selection switch 700 includes four ranges: <15mA, Off, 10mA~60mA, and 40mA~500mA. Among them, <15mA, 0mA~60mA, and 40mA~500mA correspond to different internal resistor R circuits.

[0074] According to Ohm's law, the final output leakage current value I is determined by the formula I=U / R. Since the voltage U is a fixed AC60V, by adjusting the resistor R, any desired simulated leakage current value from 5mA to 500mA can be stably generated within the selected range. The generated current is output to 301 via the second interface. When no external monitoring instrument is required, this pair of terminals must be shorted with a shorting cap to form a complete current path.

[0075] See Figure 1 and Figure 2 In one embodiment, the main housing 100 includes a front panel and a rear panel. The test interface group, voltage adjustment knob 502, resistance adjustment knob 501, current adjustment knob 503, first control switch 401, second control switch 402, and range selection switch 700 are disposed on the front panel. The power selection switch 601, single-phase power input port, and three-phase power input port are all disposed on the rear panel, and the power input interface 200 is also disposed on the rear panel.

[0076] In this embodiment, the front and rear panels are used to achieve functional zoning and separation of high and low voltage circuits, thereby optimizing the operation process and improving safety. All components requiring frequent user operation and observation, including test interfaces, adjustment knobs, function switches, and displays, are centrally located on the front panel. This allows a series of testing actions, such as wiring, setting, and reading, to be efficiently completed within a user-facing area, greatly improving ergonomics and convenience. Simultaneously, all power interfaces, such as power input, test power connection, and power selection switch 601, are centrally located on the rear panel. This isolates high-voltage, interference-prone power connections from the low-voltage operating area, effectively preventing accidental power contact, simplifying the complexity of the front panel layout, and making overall cable management more organized.

[0077] In one implementation, the second interface 301 is configured to either connect an external ammeter or be in a short-circuited state.

[0078] External ammeter status: When the test task requires higher accuracy in current measurement, the user can connect the test leads of a higher-precision external current monitoring instrument to the two terminals of the second interface 301; at this time, all the current signals generated by the leakage current test circuit will flow through this external instrument, thereby achieving more accurate measurement and recording of the output current.

[0079] Short-circuit state: When no external instrument is needed and only the built-in current display meter 801 is used for monitoring, this second interface 301 must be in the short-circuit state. It is understood that the test instrument in this solution is typically connected between the two sockets of this pair of terminals using a dedicated metal short-circuit cap provided with the instrument, to provide a low-impedance DC path for the leakage current test circuit. If not short-circuited, the current loop is in an open-circuit state, the circuit will not be able to output the set current, and the instrument function will be disabled.

[0080] In one embodiment, a cooling fan is also provided inside the main housing 100, and the airflow path of the cooling fan passes through the area where the leakage current test circuit is located.

[0081] In this embodiment, a DC cooling fan is fixedly mounted on the internal frame or circuit board bracket of the main housing 100. Optionally, the cooling fan is a small axial fan, and the main direction of the axial airflow generated by the cooling fan can cover the area where the leakage current test circuit is located.

[0082] Because the leakage current test circuit generates significant Joule heat in its internal power resistor when simulating large leakage currents, causing a rapid rise in local temperature, the cooling fan is configured as an active forced air cooling device. When operating, a continuous airflow directly blows onto or flows over the surface of the heat-generating element, quickly removing the heat generated by the element through convection heat transfer. Its core function is to establish active heat dissipation conditions for the target heat-generating area, effectively reducing the junction temperature of the power element and the surrounding ambient temperature. This ensures that the resistance value of the power resistor remains stable even during prolonged full-load testing or in high-temperature environments.

[0083] See Figure 2 and Figure 4 Furthermore, an air inlet 102 is provided on the rear panel, and the position of the air inlet 102 corresponds to the air intake side of the cooling fan; an air outlet 103 is provided on the left and / or right sides of the main body shell 100, and the air outlet 103 corresponds to the air duct of the cooling fan.

[0084] In this application, on the rear panel, in the area behind the air intake side of the cooling fan, an array of air intake holes 102 are provided. Optionally, the air intake holes 102 are multiple densely distributed circular holes or small louver-type openings, and their positions correspond to the air intake of the fan in the vertical projection.

[0085] An air outlet 103 is provided on the left and / or right side walls of the main housing 100, corresponding to the downstream of the airflow path of the cooling fan or the end of the air duct. Optionally, the air outlet 103 is a horizontal or oblique grid-like or elongated opening.

[0086] The air inlet 102 and air outlet 103 are respectively located on the rear panel and side panel to achieve directional and short airflow path, avoid airflow turbulence inside the shell or hot air recirculation, thereby improving heat dissipation efficiency.

[0087] In one embodiment, the resistance adjustment knob 501 is used to adjust the grounding resistance value in the range of 0-100kΩ, the voltage adjustment knob 502 is used to adjust the leakage voltage value in the range of 0-60V, and the current adjustment knob 503 is used to adjust the leakage current value in the range of 5mA-500mA. The adjustment range of the current adjustment knob 503 is set by the range selection switch 700.

[0088] The resistance adjustment knob 501 is used to adjust the simulated value of the grounding resistance. The effective adjustment range is set to 0-100kΩ. The 0-100kΩ range design covers the full-state test requirements from excellent grounding to severe insulation degradation or near-open circuit, and can verify the response threshold of the grounding resistance alarm device under different fault levels.

[0089] The voltage adjustment knob 502 is configured to adjust the simulated leakage voltage value, with an effective adjustment range set to 0-60V. The upper limit of the 0-60V range is set according to the general upper limit of safety extra-low voltage (SELV) and related safety standards to ensure that the early warning and protection functions of the insulation monitoring equipment can be effectively tested before dangerous voltages occur.

[0090] The current adjustment knob 503 is configured to adjust the simulated leakage current value, with a total adjustment range of 5mA-500mA. This comprehensively covers multiple levels of safety standards and test scenarios, from human perception current thresholds and dangerous ventricular fibrillation thresholds to equipment circuit protection operating currents.

[0091] In one embodiment, a marking part is also provided on the main body shell 100 at the lower end of the parameter regulator, the marking part being used to indicate the adjustment direction of the parameter regulator.

[0092] In this embodiment, clear markings are printed or engraved on the lower ends of the resistance adjustment knob 501, voltage adjustment knob 502, and current adjustment knob 503 on the main housing 100. These markings visually indicate the adjustment direction and numerical trend of the knob to the operator. Each marking includes a clear arrow symbol or a graduated arc-shaped area. For example, the marking is a straight line with arrows at both ends, with the left arrow indicating a small value and the right arrow indicating a large value. This enhances the intuitiveness and accuracy of operation, helping users to quickly and accurately set parameters.

[0093] See Figure 1In one embodiment, the range selection switch 700 is a mechanical switch with multiple fixed positions, including at least a first position, a second position, and a third position, which correspond to leakage current adjustment ranges of less than 15mA, 10mA-60mA, and 40mA-500mA, respectively.

[0094] In this application, the first setting corresponds to a current adjustment range of <15mA; the second setting corresponds to a current adjustment range of 10mA to 60mA; and the third setting corresponds to a current adjustment range of 40mA to 500mA. Each setting has a corresponding range marking on the housing.

[0095] In this application, the range selection switch 700 is connected in series between the output terminal of the current adjustment knob 503 and the leakage current test circuit. By rotating this switch to select different ranges, the user essentially switches the feedback resistor network inside the leakage current test circuit, thereby changing the amplification factor or reference of the entire current generation circuit. The rotation angle of the same current adjustment knob 503 can be adjusted within the three different and more precise current output ranges mentioned above, which is used to set an appropriate range for leakage current testing, ensuring both adjustment accuracy at low currents and output capability at high currents.

[0096] In one implementation, see Figures 1 to 3 The top of the main body shell 100 is provided with a handle 101.

[0097] Furthermore, two fixing seats are arranged opposite each other on the top of the main body shell 100, and the two ends of the handle 101 are respectively fixed in the fixing seats. The middle part of the handle 101 is arc-shaped with an opening facing the main body shell.

[0098] In this application, the two ends of the handle 101 are symmetrically connected to the corresponding mounting structures on both sides of the top of the main housing 100 via pivots or fixed supports, allowing it to bear weight when lifted and lie flat against the housing surface to save space when lowered. Optionally, the handle 101 is made of metal, and the surface may have anti-slip textures or be covered with insulating material. The handle 101 provides a convenient carrying point for the user. Considering that the instrument contains test circuits, cooling fans, and multiple meters, the whole machine has a certain weight, for example, 10kg. The handle 101 allows the operator to easily and steadily lift and move the entire instrument with one hand, greatly facilitating transfer and on-site testing operations in the field, workshop, or between different equipment.

[0099] Furthermore, a nameplate is also provided on one side of the outer casing of the handle 101; the nameplate is made of corrosion-resistant metal sheet or engineering plastic and is fixed by riveting, pasting or laser engraving. The nameplate clearly and permanently records the key identification information of the product, including at least: product name, product model, serial number, date of manufacture and manufacturer.

[0100] In some preferred embodiments, the main housing 100 is configured with a width of 252mm ± 2mm, a height of 198mm ± 2mm, and a depth of 237mm ± 2mm, and is made of cold-rolled steel sheet. This compact size design ensures the feasibility of integrating the three major test circuits—grounding resistance, leakage voltage, and leakage current—into a single chassis. Simultaneously, the ±2mm tolerance provides reasonable process tolerances for sheet metal processing, welding, and assembly in mass production, ensuring product consistency and reliability. Furthermore, the use of cold-rolled steel sheet for the main housing 100 provides excellent mechanical strength, rigidity, and impact resistance, offering robust physical protection for the internal precision test circuits and effectively resisting bumps and vibrations that may occur during field handling and vehicle transportation. At the same time, the good conductivity of cold-rolled steel sheet facilitates overall electromagnetic shielding and safe grounding.

[0101] The above description is merely an exemplary embodiment of the present utility model and does not limit the patent scope of the present utility model. Any equivalent structural transformations made based on the technical concept of the present utility model and the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present utility model.

Claims

1. A safety testing instrument, characterized in that, include: The main body casing, the test interface group disposed on the main body casing, the leakage voltage and grounding resistance test circuit and the leakage current test circuit disposed inside the main body casing; The test interface group includes at least a first interface pair for connecting the device under test and a second interface pair for connecting an external current monitoring device; The leakage voltage and grounding resistance test circuit includes: a first isolation transformer, a voltage adjustment knob, a resistance adjustment knob, a first control switch, and a second control switch; The second control switch has a common terminal, a first selection terminal, and a second selection terminal; The output terminal of the first isolation transformer is connected to the common terminal of the second control switch; The first selection terminal is connected to the input terminal of the voltage adjustment knob, and the output terminal of the voltage adjustment knob is connected to a voltage display meter; The second selection terminal is connected to the input terminal of the first control switch; the first control switch is configured to selectively switch its input terminal to the input terminal of the resistance adjustment knob or the first interface pair, and the output terminal of the first control switch is connected to a resistance display meter; The leakage current test circuit includes: a power selection switch, a second isolation transformer, a range selection switch, and a current adjustment knob. The input terminal of the power selection switch is used to selectively connect to one phase of a single-phase AC power supply or a three-phase AC power supply, and the output terminal is connected to the input terminal of the second isolation transformer. The output terminal of the second isolation transformer, the range selection switch, and the current adjustment knob are connected in series in sequence, and the output terminal of the current adjustment knob is connected to a current display meter. The voltage adjustment knob, resistance adjustment knob, current adjustment knob, first control switch, second control switch, voltage display meter, current display meter, resistance display meter, and range selection switch are all located on the main body shell.

2. The safety testing instrument as described in claim 1, characterized in that, The main body housing includes a front panel and a rear panel. The test interface group, voltage adjustment knob, resistance adjustment knob, current adjustment knob, first control switch, second control switch and range selection switch are disposed on the front panel; the power selection switch, single-phase power input and three-phase power input are disposed on the rear panel.

3. The safety testing instrument as described in claim 1, characterized in that, The second interface is configured to either connect an external ammeter or be in a short-circuited state.

4. The safety testing instrument as described in claim 2, characterized in that, The main housing is also equipped with a cooling fan, and the airflow path of the cooling fan passes through the area where the leakage current test circuit is located.

5. The safety testing instrument as described in claim 4, characterized in that, An air inlet is provided on the rear panel, and the position of the air inlet corresponds to the air intake side of the cooling fan; an air outlet is provided on the left and / or right side of the main body shell, and the air outlet corresponds to the air duct of the cooling fan.

6. The safety testing instrument as described in claim 1, characterized in that, The resistance adjustment knob is used to adjust the grounding resistance value in the range of 0-100kΩ, the voltage adjustment knob is used to adjust the leakage voltage value in the range of 0-60V, and the current adjustment knob is used to adjust the leakage current value in the range of 5mA-500mA. The adjustment range of the current adjustment knob is set by the range selection switch.

7. The safety testing instrument as described in claim 6, characterized in that, The range selection switch is a mechanical switch with multiple fixed positions, including at least a first position, a second position, and a third position, which correspond to leakage current adjustment ranges of less than 15mA, 10mA-60mA, and 40mA-500mA, respectively.

8. The safety testing instrument as described in claim 6, characterized in that, The main body shell is also provided with an indicator at the lower end of the resistance adjustment knob, voltage adjustment knob and current adjustment knob, the indicator being used to indicate the adjustment direction of each knob.

9. The safety testing instrument as described in claim 1, characterized in that, The main body shell is equipped with a handle.

10. The safety testing instrument as described in claim 9, characterized in that, The top of the main body shell has two fixed seats opposite each other, and the two ends of the handle are respectively fixed in the fixed seats. The middle part of the handle is an arc shape with an opening facing the main body shell.

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