Screwdriver for measuring contact resistance and measuring method

Abstract

The invention relates to the technical field of equipment maintenance, and discloses a screwdriver for measuring contact resistance and a measuring method.The screwdriver comprises a screwdriver body, a replaceable conductive tool bit is arranged at the front end of the screwdriver body, an internal driving shaft is connected with the replaceable conductive tool bit, and an expansion line interface is further formed in the screwdriver body; a torque unit, a processing control unit, a voltage detection unit and a current source are integrated in the screwdriver body, and the processing control unit is in communication connection with the torque unit, the current source and the voltage detection unit. According to the invention, the existing wiring harness of the maintained equipment is utilized to form a measurement loop, an additional complex test wire clamp is not needed, the method is especially suitable for a field maintenance scene of intensive terminal strips such as a PLC module, and convenient and independent measurement of inner and outer side contact points of a double-screw terminal is supported.

Description

Technical Field

[0001] This invention relates to the field of equipment maintenance technology, and in particular to a screwdriver and a method for measuring contact resistance. Background Technology

[0002] In the maintenance of industrial automation and electrical control cabinets, the reliability of terminal block connections is crucial. A reliable connection must possess both good mechanical tightness and excellent electrical conductivity. The existing process involves steps: operators use tools to tighten screws to the specified torque, then switch to a contact resistance tester to measure whether the point is within acceptable limits. The drawbacks of this traditional method are that the operation requires switching tools, impacting efficiency during heavy maintenance workloads; furthermore, the tightening action and electrical measurement results are independent in terms of time and recording, making timely assessment impossible.

[0003] Currently, there is a lack of a tool that can integrate fastening and measurement functions, that is, to complete contact resistance measurement and instant judgment when a specified torque is reached. Summary of the Invention

[0004] The purpose of this invention is to provide a screwdriver and a method for measuring contact resistance, which aims to achieve simultaneous automatic measurement, judgment and recording of contact resistance during one-time tightening of terminals, and solve the problems of lack of professional tools and inconvenient operation in the prior art.

[0005] This invention is achieved through the following scheme: A screwdriver for measuring contact resistance includes: a screwdriver body, which integrates a torque unit, a processing control unit, a voltage detection unit, and a current source; A replaceable conductive tip is replaceably mounted on the front end of the screwdriver body and electrically connected to the output terminal of a current source; The drive shaft is driven by a torque unit and rotates the replaceable conductive blade head. An extension line interface is located on the screwdriver body and is electrically connected to the return terminal of the current source and the input terminal of the voltage detection unit. The processing control unit is communicatively connected to the torque unit, current source, and voltage detection unit, and performs the following operations: S1: Receives torque signal from torque unit; S2: When the torque signal indicates that the torque value has reached the preset threshold, a command is sent to the current source to output a constant measurement current, and a command is sent to the voltage detection unit to start the voltage measurement. S3: Calculate the total resistance of the external circuit electrically connected between the replaceable conductive tip and the extension line interface based on the voltage measured by the voltage detection unit and the constant measuring current.

[0006] Furthermore, it also includes a prompting unit, which includes a buzzer and / or an indicator light; the processing control unit compares the calculated total resistance value with a preset resistance threshold range, and controls the prompting unit to issue a corresponding prompting signal based on the comparison result.

[0007] Furthermore, it also includes a data storage unit; the processing control unit associates and stores one or more of the following: torque value, total resistance value, operation timestamp, and corresponding terminal identification information, into the data storage unit.

[0008] Furthermore, a handle is connected to the rear end of the screwdriver body, and a start button is set on the handle.

[0009] Furthermore, the replaceable conductive tip makes electrical contact with the target screw at the terminal block, and the wiring harness is connected to the expansion cable interface via the terminal block and the cabinet wiring. In this case, the external circuit includes the contact resistance of the target screw.

[0010] A method for measuring contact resistance includes the following steps: S1: Connect the wire harness end of the terminal block to be tested to the expansion cable interface; S2: Use a replaceable conductive tip to tighten the target screw of the terminal under test; S3: The tightening torque is monitored by the torque unit, and the resistance measurement process is automatically triggered by the processing control unit when the tightening torque reaches the preset threshold. S4: In the resistance measurement process, the current source outputs a constant measurement current, which flows through a current loop consisting of a replaceable conductive tip, target screw, terminal block body, wire harness and extension wire interface. At the same time, the voltage detection unit measures the voltage of the current loop. S5: The processing control unit calculates the total resistance of the current loop based on the voltage and constant measured current.

[0011] Furthermore, after calculating the total resistance value, the method also includes a step of comparing the total resistance value with a preset acceptable range and generating an audio-visual prompt signal to indicate the comparison result.

[0012] Furthermore, a step of waiting for a predetermined delay time is included before triggering the resistance measurement process.

[0013] Furthermore, the method also includes measuring the contact resistance of another screw on the terminal block under test after completing the measurement of the target screw, and repeating the above steps.

[0014] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: This system combines tightening and measurement into a single, simultaneous operation, simplifying on-site procedures. Utilizing the maintained wiring harness itself to form the measurement loop eliminates the need for external test clamps, making it suitable for maintenance scenarios involving dense terminal blocks. It allows for independent measurement of the inner and outer screws of a single terminal. Measurement is performed after the final tightening torque is reached, and audible and visual prompts indicate whether the result is satisfactory, providing rapid feedback on the outcome. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the screwdriver structure of the present invention; Figure 2 This is a schematic diagram of the screwdriver measurement connection of the present invention; Figure 3 This is a block diagram of the screwdriver measuring unit of the present invention; Figure 4 This is the circuit diagram of the screwdriver of this invention; Figure label: 100-Screwdriver body; 110-Torque unit; 120-Processing control unit; 130-Current source; 140-Voltage detection unit; 150-Indication unit; 160-Data storage unit; 200-Replaceable conductive tip; 300-Extension cable interface; 400-Handle; 500-Start button; 600-Terminal; 601-Target screw; 602-Internal wiring; 603-PLC wiring harness. Detailed Implementation

[0016] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0017] Any feature disclosed in this specification (including any appended claims and abstract) may be replaced by other equivalent or similar features, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features.

[0018] In the description of this invention, it should be understood that the terms "upper", "lower", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0019] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature.

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. These descriptions are exemplary and are not intended to limit the scope of protection of this invention.

[0021] See Figures 1-4 This invention illustrates a specific embodiment of a screwdriver for measuring contact resistance. Externally, it consists of a screwdriver tip and a PLC wiring harness 603 connected to the screwdriver from a terminal block. The PLC wiring harness 603 itself is incorporated into a measurement circuit, where current and voltage are measured internally within the screwdriver body 100. The screwdriver body 100 integrates a torque unit 110, a processing control unit 120, a voltage detection unit 140, and a current source 130. A replaceable conductive tip is mounted at the front end of the body, connecting to a drive shaft for torque transmission; its interface provides both mechanical and electrical connection. An extension cable interface 300 is located on the screwdriver body 100 for connecting external wires. A handle 400 is connected to the rear end of the screwdriver body 100 for manual tightening, and a start button 500 is located on the handle 400.

[0022] A replaceable conductive cutting tip 200 is mounted on the front end of the main body via an interface, serving as both a screw-tightening tool and a current injection electrode. A drive shaft transmits power from the torque unit 110 to the cutting tip. An extension line interface 300 is located on the side or rear of the main body, connected to the input terminal of the voltage detection unit 140, and electrically connected to the output terminal of the current source 130. Specifically, the replaceable conductive cutting tip 200 makes electrical contact with the first screw at the terminal block 600, and the terminal block 600, along with the cabinet wire 602, is connected to the extension line interface 300 via a wire harness 603. In this case, the external circuit includes the contact resistance of the first screw.

[0023] Through the above structure, a measurement loop is constructed: when tightening a screw at the target terminal 600, such as the outer screw, the wire of the PLC wiring harness connected to the terminal is first connected to the expansion cable interface 300; when the torque reaches the set value, the system automatically triggers the constant current output by the current source 130 to flow through the loop consisting of the cutting head, the contact surface of the screw being tested, the terminal, and the connected wire; the voltage detection unit 140 measures the total voltage drop of the loop; the processing control unit 120 calculates the loop resistance based on this, and the resistance value directly reflects the contact quality of the screw being tested, and can immediately perform qualification judgment and data recording. For the terminal 600 with two screws, by exchanging the screw being tested and the wire connection terminal, the independent measurement of the inner and outer screws can be completed separately.

[0024] It also includes a prompting unit 150, which is a buzzer and an indicator light; the processing control unit 120 compares the calculated total resistance value with a preset resistance threshold range, and controls the prompting unit 150 to issue a corresponding prompting signal according to the comparison result.

[0025] It also includes a data storage unit 160; the processing control unit 120 associates and stores one or more of the torque value, the total resistance value, the operation timestamp and the corresponding terminal identification information in the data storage unit 160.

[0026] The processing control unit 120 is communicatively connected to the torque unit 110, the current source 130, and the voltage detection unit 140, and performs the following operations: First, it receives a torque signal from the torque unit 110; second, when the torque signal indicates that the torque value reaches a preset threshold, it sends a command to the current source 130 to output a constant measuring current, and simultaneously sends a command to the voltage detection unit 140 to start voltage measurement; finally, based on the voltage measured by the voltage detection unit 140 and the constant measuring current, it calculates the total resistance value of the external circuit electrically connected between the replaceable conductive blade 200 and the extension line interface 300.

[0027] The present invention also provides a method for measuring contact resistance using the above-described system. The method includes the following steps: S1: Disconnect one of the wires already connected to the target terminal and connect its conductor end to the screwdriver's extension cable connector.

[0028] S2: Use a replaceable conductive tip to tighten the target screw of the terminal under test; S3: The tightening torque is monitored by the torque unit, and when the tightening torque reaches a preset threshold, the processing control unit automatically triggers the resistance measurement process; after the torque value reaches the preset threshold, the processing control unit sends a start command to the current source and the voltage detection unit; specifically, the threshold range is 0.05Ω-0.1Ω.

[0029] S4: In the resistance measurement process, the current source 130 outputs a constant measurement current, which flows through a complete circuit consisting of the replaceable conductive blade 200, the target screw 601, the terminal block 600, the wire harness 603, and the extension wire interface 300. At the same time, the voltage detection unit measures the voltage of the circuit and calculates the total resistance of the circuit according to Ohm's law.

[0030] S5: The processing control unit calculates the total resistance value of the current loop based on the voltage and the constant measuring current. After calculating the total resistance value, it stores the relevant data and compares the total resistance value with a preset qualified range. Based on the comparison result, it controls the prompting unit to issue different audible and visual prompt signals to achieve immediate and intuitive feedback on the measurement results.

[0031] After completing the measurement of the target screw 601, measure the contact resistance of another screw on the terminal to be tested, and repeat the above steps.

[0032] Optionally, in order to eliminate the instantaneous impact of mechanical vibration on electrical contact at the moment the fastening action stops and improve measurement stability, the processing control unit will control the program to wait for a short time interval, such as 100-500 milliseconds, after the torque value reaches the preset threshold before sending a start command to the current source and voltage detection unit, thereby triggering the measurement process.

[0033] Working Principle: According to the cable list, tighten each terminal corresponding to the PLC output terminal. Each terminal 600 has two wiring screws (inner and outer), allowing for two measurements. The PLC wiring harness 603 typically has 16 or more wires, each connected to a terminal. During operation, disconnect the terminal and connect it to the interface of the smart screwdriver. The screwdriver's mechanical structure is electrically powered with torque feedback. When the torque is reached, it stops working, and the screwdriver head acts as the current output terminal. The current flows through terminal 600 to the PLC wiring harness 603 wire and back to the screwdriver's interior. A constant current is sent internally, and the voltage at the current output and input terminals is measured. This allows calculation of the voltage across the screwdriver from the terminal to the wire and back to the screwdriver's interior, ultimately calculating the resistance of this loop. Thus, tightening the screwdriver on a particular circuit forms a complete loop with terminal 600 and the cabinet wiring 602 for that circuit.

[0034] Excessive tightening force when tightening inner and outer screws can damage the terminals. Therefore, the tightening degree is determined by the torque. After reaching the tightening torque, the circuit resistance is automatically measured and the data is recorded. An alarm is triggered if there is an abnormality. For connection points such as wiring terminals and line connectors in the PLC measurement circuit, oxidation or loosening can significantly increase contact resistance, potentially leading to attenuation of analog signals or abnormal transmission of digital signals. Therefore, in actual maintenance, the contact resistance of these contacts must be controlled within the range of 0.05Ω-0.1Ω.

[0035] This invention utilizes the existing wiring harness of the device being maintained to form a measurement circuit, eliminating the need for additional complex test clamps. It is particularly suitable for on-site maintenance scenarios involving dense terminal blocks such as PLC modules, and supports convenient and independent measurement of the inner and outer contact points of double-screw terminals.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A screwdriver for measuring contact resistance, characterized in that, include: The screwdriver body (100) integrates a torque unit (110), a processing control unit (120), a voltage detection unit (140), and a current source (130). A replaceable conductive tip (200) is replaceably disposed at the front end of the screwdriver body (100) and electrically connected to the output end of the current source (130); The drive shaft is driven by the torque unit (110) and drives the replaceable conductive blade (200) to rotate; An extension line interface (300) is provided on the screwdriver body (100) and electrically connected to the return terminal of the current source (130) and the input terminal of the voltage detection unit (140); The processing control unit (120) is communicatively connected to the torque unit (110), the current source (130), and the voltage detection unit (140), and performs the following operations: S1: Receive torque signal from the torque unit (110); S2: When the torque signal indicates that the torque value has reached the preset threshold, a command is sent to the current source (130) to output a constant measurement current, and a command is sent to the voltage detection unit (140) to start the voltage measurement. S3: Calculate the total resistance of the external circuit electrically connected between the replaceable conductive blade (200) and the extension line interface (300) based on the voltage measured by the voltage detection unit (140) and the constant measuring current.

2. A screwdriver for measuring contact resistance according to claim 1, characterized in that, It also includes a prompting unit (150), which includes a buzzer (151) and / or an indicator light (152); the processing control unit (120) compares the calculated total resistance value with a preset resistance threshold range, and controls the prompting unit (150) to issue a corresponding prompting signal according to the comparison result.

3. A screwdriver for measuring contact resistance according to claim 1, characterized in that, It also includes a data storage unit (160); the processing control unit (120) associates and stores one or more of the torque value, the total resistance value, the operation timestamp and the corresponding terminal identification information in the data storage unit (160).

4. A screwdriver for measuring contact resistance according to claim 1, characterized in that, The screwdriver body (100) has a handle (400) connected to its rear end, and a start button (500) is provided on the handle (400).

5. A screwdriver for measuring contact resistance according to claim 1, characterized in that, The replaceable conductive tip (200) makes electrical contact with the target screw of the terminal block, and is connected to the extension line interface (300) by a wire harness through the terminal block with internal wiring. At this time, the external circuit includes the contact resistance of the target screw.

6. A method for measuring contact resistance, using a screwdriver for measuring contact resistance as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1: Connect the wire harness end of a terminal block to be tested to the expansion cable interface (300). S2: Use the replaceable conductive tip (200) to tighten the target screw of the terminal to be tested; S3: The torque unit (110) monitors the tightening torque, and when the tightening torque reaches a preset threshold, the processing control unit (120) automatically triggers the resistance measurement process. S4: In the resistance measurement process, the current source (130) outputs a constant measurement current, which flows through a current loop consisting of a replaceable conductive blade (200), a target screw, a terminal block, a wire harness, and an extension wire interface (300), while the voltage detection unit (140) measures the voltage of the current loop. S5: The processing control unit (120) calculates the total resistance value of the current loop based on the voltage and constant measured current.

7. The contact resistance measurement method according to claim 6, characterized in that, After calculating the total resistance value, the method further includes a step of comparing the total resistance value with a preset acceptable range and generating an audio-visual prompt signal to indicate the comparison result.

8. The contact resistance measurement method according to claim 6 or 7, characterized in that, Before triggering the resistance measurement process, a step of waiting for a predetermined delay time is also included.

9. The contact resistance measurement method according to claim 8, characterized in that, It also includes measuring the contact resistance of another screw on the terminal under test after completing the measurement of the target screw, and repeating the above steps.

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