Definition
A pressure spring torque meter is a mechanical measuring instrument used to measure the torque or rotational force subjected to rotating parts. Its core measuring element is a coil compression spring, which indicates the torque value by the deformation of the spring under the action of torque. Due to their simple structure, easy portability, and direct readings, this type of instrument is widely used in many non-medical fields such as industrial production, quality control, and equipment maintenance.
Principle
The working principle of the pressure spring torque gauge is based on Hooke's law and the principle of lever balance. When the measured torque is applied to the instrument spindle through a drive tenon or sleeve, the torque is transferred to a precision-calibrated coil compression spring. The spring produces compression deformation under the action of torque, and its deformation is directly proportional to the torque it receives. The deformation is amplified by a set of levers or gear mechanisms and drives the pointer to deflect on a circular dial, thus directly indicating the torque value. Its core relationship can be expressed as:
M = k · θ
where M represents torque, k is the torsional stiffness coefficient of the spring, and θ is the angular displacement of the spring or the corresponding pointer deflection angle.
Measurement method
Measuring with a pressure spring torque meter typically follows a standardized process. First, select an instrument with a suitable range according to the estimated torque value to ensure that the measured torque is within the range of 20% to 80% of its range. Second, the drive head of the instrument (such as a square tenon or sleeve) is reliably connected to the rotating axis of the system under test. When measuring, the rotational force should be applied smoothly and uniformly along the axis of the instrument spindle to avoid shock loads. Read the torque value when the pointer indicates stability. For applications where peak torque needs to be recorded, some models are equipped with a peak hold function. After the measurement is completed, the value should be set to zero, and the instrument should be properly stored in a special box to avoid the spring being stressed for a long time.
Influencing factors
The measurement accuracy of a spring torque gauge can be affected by several factors. Changes in ambient temperature can cause small changes in the spring rate coefficient, which can cause readings to drift. The instrument's mounting is moderate, i.e., whether the direction of the applied force is completely parallel to the spindle axis, which affects the accuracy of the measurement results. The speed and uniformity of the operator's force are also critical factors, and rapid impact can lead to pointer overshoot. In addition, the condition of the instrument itself, such as spring fatigue, wear or lubrication of mechanical components, and whether it is calibrated on time after long-term use, can affect measurement reliability.
Applications
Spring torque gauges play an important role in numerous industries and technologies. In the electronic and electrical industry, it is used to measure the assembly torque of micro screws and potentiometers. In automobile manufacturing and maintenance, it is used for the fastening force control of spark plugs, tire nuts, and engine head bolts. In the packaging industry, it is used to detect the tightening torque of bottle caps. In materials research, it can be used to evaluate the rotational friction properties of small components. In addition, it is often used as a tool for rapid on-site inspection in aerospace, precision instrument assembly, and other occasions where tightening force is strictly required.
Selection considerations
When choosing a pressure spring torque meter, multiple technical parameters need to be taken into account. Range is the primary factor, covering the conventional range of the torque being measured with a margin. The resolution should meet the requirements of measurement accuracy. The size and shape of the drive head (e.g., square, hexagonal, or pin) must match the part being measured. Considering the reading, the dial pointer is intuitive and the digital is easy to record and data output. It is also important to pay attention to the accuracy level of the instrument, which is usually expressed as a percentage of full scale. Other factors include the need for peak hold, bidirectional measurement capability in both forward and counterclockwise directions, and whether the instrument size and weight meet field operating conditions. Finally, confirming that the instrument has a traceable calibration certificate and complies with relevant national or international standards is the basis for ensuring the validity of the measurement.