High-frequency test points for Mechanical and Electrical Engineering in the First-Class Constructor Exam: Automation instruments
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1. Instrument debugging and calibration ✅ Key point: Stability of the test power supply； The standard instrument error ≤ 1/3 of the error of the instrument being calibrated ； Calibration points should be selected evenly (≥5 points for a single device, ≥3 points for a circuit). 💡 Mnemonic: Ensure stable power supply for accurate calibration; 3% error with 5 or 3 points
📌 2024 First-Class Constructor Exam: Mechanical and Electrical Engineering – True Questions (Single Choice) – Question 8: Regarding the procedures for commissioning automated instruments, which of the following is correct? A. The power supply voltage remains stable during instrument testing.
B. Loop testing can be conducted after the system is put into service.
C. The absolute value of the basic error of the test instruments is greater than that of the instruments being tested.
D. The calibration points for each individual instrument are selected randomly within the instrument’s full measurement range
B. Loop testing can be conducted after the system is put into service.
C. The absolute value of the basic error of the test instruments is greater than that of the instruments being tested.
D. The calibration points for each individual instrument are selected randomly within the instrument’s full measurement range
Answer: A 🔍 Explanation: A is correct; the power supply voltage for instrument testing should be stable. B is incorrect; loop testing should be conducted before the system is put into service. C is incorrect; the error of the standard instrument should be ≤ 1/3 of that of the instrument being calibrated. D is incorrect. Calibration points should be selected uniformly, not randomly.
2. Installation of instrument piping ✅ Key point: Pipes buried directly underground must be welded； Stainless steel pipe and carbon steel bracket with isolation pads ； Bending radius of high-pressure steel pipes ≥ 5 times the outer diameter ； Spacing of steel pipe supports: 1.0–1.5 m horizontally, 1.5–2.0 m vertically. 💡 Mnemonic: Use insulation for buried welds; when the bend radius is five times the pipe diameter, place supports more frequently
📌 2025 First-Class Constructor Mechanical and Electrical Real Exam (Single Choice) – Question 19: Which of the following statements regarding the general regulations for instrument pipeline construction is incorrect? A. Welding must be used for the connections of pipes that are buried directly in the ground. B. A gasket should be placed between stainless steel pipes and carbon steel supports. C. The spacing between horizontal supports for steel pipe instrumentation systems should be 2 to 3 meters. D. The bending radius of high-pressure steel pipes should be greater than 5 times the outer diameter of the pipes
Answer: C 🔍 Explanation: Option C is incorrect. For horizontally installed steel pipes, the spacing between supports should be 1.00–1.50 m; for vertically installed pipes, it should be 1.50–2.00 m. A, B, and D are all correct.
3. Installation of temperature detection instruments ✅ Key point: The sensing element of pressure-type thermometers must be fully submerged； Bending prevention measures are taken at the impacted area ； Take anti-wear measures in dusty environments ； The surface thermometer must be in close contact with the surface. 💡 Mnemonic: Apply full pressure; prevent bending from impacts; protect against wear caused by dust; ensure close surface contact
📌 2023 First-Class Constructor Exam: Mechanical and Electrical Engineering – True Questions (Single Choice) – Question 6: Which of the following statements regarding the installation of temperature measuring instruments is incorrect? A. Anti-bending measures should be taken when installing in locations subject to strong impacts from materials. B. The temperature sensing bulb of a pressure-type thermometer should be mostly immersed in the medium being measured. C. Wear prevention measures should be implemented for temperature measuring elements installed in dusty environments. D. The temperature sensing surface of a surface thermometer must make close contact with the surface of the object being measured
Answer: B 🔍 Explanation: B is incorrect; the sensor bulb of a pressure-type thermometer must be completely submerged in the substance being measured, not just “mostly”.
For reference: There are two possible orders for the subjects that need to be studied for the First-Class Constructor exam. One is to start with the more difficult subjects first, namely Management → Practice → Economics → Regulations. In this approach, one first tackles the more complex management and practical aspects that are closely related to each other, and once those are handled, dealing with economics and regulations becomes much easier. Another approach is to start with the easier tasks first: regulations → economics → management → practical applications. This is a gradual approach, making it difficult to feel discouraged when faced with difficulties. Each of the above has its own advantages and disadvantages.
The case study questions in the First-Class Constructor Mechanical and Electrical Practice section are really tough; there are answering strategies that can help improve scores. The case analysis questions in the Mechanical and Electrical Practice section of the First-Class Constructor exam are key points and difficulties in the test; candidates are usually required to conduct comprehensive analyses by integrating practical engineering knowledge, regulatory standards, and management principles.