1. Accuracy
Definition: Refers to the degree to which the sensor measurement results are close to the true value, usually expressed as a percentage, such as 0.1%, 0.5%, etc.
Influencing factors: uniformity of elastic component materials, stability of elastic modulus, dimensional accuracy and surface roughness during processing, linearity and sensitivity of sensitive components such as strain gauges, as well as accuracy of amplifiers and characteristics of filters in signal processing circuits. For example, in the aerospace field, engine torque measurement requires extremely high accuracy, and small errors may lead to deviations in engine performance evaluation, affecting flight safety. Therefore, high-precision torque sensors with an accuracy of 0.1% or even higher are needed.
Range
Definition: It refers to the torque range that a sensor can measure, including the minimum measurable torque and the maximum measurable torque.
Selection criteria: It is necessary to comprehensively consider the torque during normal operation of the equipment, the impact torque during startup and braking, and the possible overload torque. It is generally recommended to select a range greater than 20% -30% of the estimated maximum torque to ensure the safe and reliable operation of the sensor. For example, in the drive system of a large fan, the torque during startup is relatively high. If the estimated maximum startup torque is 5000 N · m, a torque sensor with a range of at least 6000 N · m should be selected.
Response time
Definition: Refers to the time interval from the change in torque to the corresponding change and stabilization of the sensor output signal.
Importance: It is crucial in dynamic torque measurement. For example, during the acceleration and deceleration process of a car engine, the torque changes frequently in an instant. Only sensors with short response times, such as those that can complete signal response within a few milliseconds, can accurately capture torque changes and provide timely and accurate data for the engine control system to optimize fuel injection and ignition timing, improve engine performance and fuel economy.
Stability
Definition: Refers to the ability of a sensor to maintain stable performance parameters under various environmental conditions during long-term use.
Influencing factors: Changes in environmental temperature can cause thermal expansion and contraction of elastic components, as well as changes in material properties. Humidity may affect the insulation performance of circuits and the characteristics of sensitive components. Vibration can cause loosening or deformation of the internal structure of sensors, and long-term use can also lead to material aging and performance degradation. Taking the continuous casting machine in a metallurgical plant as an example, its working environment is high temperature, humidity, and large vibration, which requires the torque sensor to have good stability and be able to work stably for a long time in such harsh environments, ensuring accurate measurement of the rotating torque of the ladle during the continuous casting process. Otherwise, frequent calibration and maintenance will affect production efficiency.
2. model selection
Application scenario adaptation:
Industrial automation: For the motor drive system of the assembly line, torque sensors with general accuracy and response speed can meet the needs of monitoring motor load and preventing overload; In the joint drive of high-precision robot arms, in order to achieve precise force control and trajectory tracking, high-precision and fast response torque sensors are needed to sense small force changes, ensuring the accuracy and flexibility of robot actions.
Automotive industry: In electronic power steering systems, torque sensors are used to measure the torque of the driver turning the steering wheel, providing control signals for the power assist motor. High precision and fast response are required to achieve sensitive and comfortable steering assistance; In automotive powertrain testing, it is necessary to measure engine output torque and transmission input/output torque, which requires torque sensors with large range, high accuracy, and the ability to adapt to complex vibration environments.
Signal output matching:
Analog signal: Voltage output type (such as 0-5V, 0-10V) torque sensor, the output signal is proportional to the torque, suitable for simple control systems with low signal processing speed requirements and close distances; Current output type (such as 4-20mA) torque sensor, with strong anti-interference ability, suitable for long-distance transmission, but requires external power supply.
Digital signal: RS485 interface torque sensor, using differential signal transmission, strong anti-interference ability, can realize network communication of multiple sensors, suitable for industrial fieldbus control systems; The torque sensor with CAN bus interface has the characteristics of high speed, reliability, and strong real-time performance, and is widely used in fields such as automotive electronics and industrial automation that require high data transmission speed and reliability.
3. maintenance
Fault diagnosis method:
Appearance inspection: Regularly inspect the sensor housing for cracks, deformation, wear, loose or corroded connections, and damaged or aged cables. If cracks are found on the outer shell, it may be caused by mechanical impact or long-term stress, and further inspection of the internal structure is required; Loose connections can cause unstable signals and should be tightened in a timely manner.
Electrical performance testing: Use a multimeter to measure the input and output resistance of the sensor and check if it is within the specified range. If the resistance value is abnormal, it may be due to an open circuit, short circuit, or component damage in the internal circuit; Use a signal generator to input standard signals and check if the output signal of the sensor is normal. If the output signal deviates significantly from the theoretical value, it indicates that there is a problem with the sensor's signal processing circuit or sensitive components.
Self diagnostic function utilization: For intelligent torque sensors with self diagnostic function, the fault type and location can be quickly located by reading the internal fault codes or status information of the sensor. For example, some sensors can automatically detect issues such as high internal temperature and zero drift, and provide corresponding prompt information.
Regular maintenance measures:
Calibration: Send the torque sensor to a professional metrology institution or use high-precision calibration equipment for calibration according to the prescribed calibration cycle. During the calibration process, by applying a known torque value, comparing the measured value of the sensor with the true value, adjusting the parameters of the sensor to ensure that its measurement accuracy meets the requirements. Generally speaking, for sensors used in high-precision measurement scenarios or harsh environments, the calibration cycle should be shortened to about six months; Sensors used in ordinary industrial environments can be calibrated once a year.
Cleaning: Regularly wipe the sensor housing and connection parts with a clean soft cloth to remove dust, oil, water vapor, and other pollutants. For some difficult to clean oil stains, a moderate amount of neutral cleaner can be used, but attention should be paid to avoiding the cleaner from entering the interior of the sensor. Sensors used in humid environments should also pay attention to preventing water vapor from condensing on the housing. Appropriate moisture-proof measures can be taken, such as adding protective coatings or using desiccants.
Check installation: Check whether the installation base of the sensor is firm, whether there is looseness or displacement; Whether the coupling is worn or deformed, and whether the connection is tight. If the installation base is found to be loose, it should be tightened in a timely manner; When the coupling is severely worn, it needs to be replaced in a timely manner to ensure the accuracy and stability of torque transmission and avoid measurement errors caused by installation problems.