Coaxial cable length and terminal load detection device (Question B) [Undergraduate Group]
1. Task
Design and build a coaxial cable length and terminal load detection device (hereinafter referred to as the "device"), as shown in Figure 1. The starting end of the cable to be tested is connected to the device through a cable connector, and the cable terminal can be open-circuited or connected to a resistive or capacitive load. Set two buttons "Length Detection" and "Load Detection" to select and start the corresponding functions. Load resistance value range: 10Ω 30Ω, capacitance value range: 100pF 300pF. The device is powered by a single power supply not greater than 6V.
2. Requirements
1. Basic requirements
- (1) The device can display the working status, cable length, load type, and load parameters. The display format is shown in Table 1.
- (2) If the cable length is 1000cm≤L≤2000cm and the terminal is open circuit, press the "Length Detection" button to start the detection. The device can detect and display the cable length L. The absolute value of the relative error is not greater than 5%, and the detection time is not more than 5s.
- (3) After completing the cable length detection under the terminal open circuit condition, keep L unchanged, connect a load of resistor or capacitor to the terminal, press the "Load Detection" button to start the detection, the device can correctly judge and display the load type, once The detection time does not exceed 5s.
2. Play part
- (1) Improve the cable length detection accuracy: if the cable length is 1000cm ≤ L ≤ 2000cm, and the terminal is open circuit, the absolute value of the relative error in cable length detection shall not be greater than 1%, and the detection time shall not exceed 5 seconds.
- (2) After the length detection is completed under the terminal open circuit condition, keep L unchanged, connect a load of resistor or capacitor to the terminal, press the "Load Detection" button to start the detection, the device will detect and detect based on the correct judgment of the load type. Display the resistance and capacitance values of the load, the absolute value of the relative error is not greater than 10%, and the detection time is not more than 5 seconds.
- (3) Reduce the blind zone of cable length detection: When the terminal is open-circuited, under the conditions that the absolute value of the relative error of cable length detection is not greater than 1% and the time of one detection does not exceed 5 seconds, the length of the cable that can be detected is reduced to L≤100cm. .
- (4) Others.
3. Description
- (1) The device should include a signal source and a measurement processing circuit. Use appropriate excitation signals according to the measurement method, measure incident, reflected and other signals at the beginning of the cable and process them to calculate the parameters required for detection.
- (2) The coaxial cable to be tested shall be prepared by the participating team and brought to the site when participating in the test. The total length of the cable must be measured in advance. The length of at least one cable shall not be less than 2000cm. The type of plug connected to the starting end of the cable is customized, and the terminal can easily connect the load between the core wire and the shielding layer. The cable should be allowed to be coiled. During the test, other than cutting the cable to the specified length and connecting the specified load, no other changes to the state of the cable are allowed.
- (3) During the evaluation process of the work, except for pressing "Length Detection" and "Load Detection" to activate the corresponding functions, no other adjustments or operations are allowed on the device.
- (4) In the question,
the actual value of the absolute value resistor and capacitor used to detect the relative error is measured using an LCR tester. - (5) In the performance part (3), the minimum detectable length L≤100cm will get full marks, and L≥1000cm will not score this item. During the test, the participating team will specify a test length, measure around this length and conduct accuracy verification. If the absolute value of the relative error in cable length measurement is no more than 1% and the test time is no more than 5 seconds, the requirements will be considered met and the length will be deemed valid.
- (6) Ranging sensors and cameras are not allowed to be used in the work.
4. Scoring Criteria
Open source reference for excellent works (source: Lichuang Open Source Platform)
- Jialichuang : https://lceda.cn/
- LiChuang open source platform : https://oshwhub.com/
- 2023 Electronic Competition Question B [Coaxial Cable Length and Terminal Load Detection
- 2023 Question B [Coaxial cable length and terminal load detection device]
- 2023 Question B [Coaxial cable length and terminal load detection device]
