Force sensors and load cells work on the same principle, but they are used for different purposes and have different measurement requirements, especially for small-range measurements.
Force measurement requires that the line of force applied to the force being measured be coaxial with the force on the sensor . Therefore, most force sensors adopt spoke-type, torsion ring-type, and column-type structures. In some cases, S-type sensors are also used as alternatives.
Torsion ring type force sensors are widely used in precision machinery and testing applications because they can be used in high-altitude spaces. Below is a brief explanation of the structure and working principle of a torsion ring type force sensor to facilitate correct selection, such as range, signal processing, etc., avoiding unnecessary measurement errors and resulting product quality problems.
We can determine whether the design and technical parameters of a sensor meet the usage requirements from the following aspects:
Metal elastomer: It may look like just a metal, but it is the force-bearing carrier. The material of the elastomer is the guarantee of the sensor's reliable technical performance in terms of force strength, durability, zero point, linearity, creep, overload resistance, etc.
Simple testing method: Maintain the force for 30 minutes, unload, and observe the zero-point recovery speed and zeroing time.
Fixed screw holes: The presence or absence of fixed screw holes on micro sensors not only requires metal materials, but also greatly increases the difficulty of processing, especially the processing of 17-4PH stainless steel.
Force-bearing endpoint R: This is a key distinguishing feature. Ordinary machining results in a simple flat surface without any curved surfaces. This makes it impossible to guarantee the consistency of force distribution, as the force cannot be applied at the tangent point of the curved surface, and the pressure varies with the force-bearing surface.
Height and diameter: Due to the limited volume of the micro-sensor and the metal elastomer, the magnitude of the force it receives will directly affect the metal's load-bearing capacity.
Some manufacturers reduce the height by increasing the diameter, which makes it easier for the strain gauge to resonate under stress and prone to yielding and damage under long-term loads. Generally, the diameter-to-height ratio is around 2:1. Manufacturing difficulty is judged by a diameter of φ10. For diameters of φ20 and above, the manufacturing difficulty is greatly reduced because strain gauges are relatively simple to manufacture.
Strain gauges: those with a diameter of φ10 or less are only imported products. For φ20 gauges, there are domestically produced alternatives. Therefore, the diameter of the sensor is also a typical indicator of the sensor's manufacturing capability.
Working principle:
When the elastic body is subjected to force and deforms, the resistance strain gauges (four gauges forming a Whitworth bridge) attached to the elastic body deform, and the resistance value changes. The bridge becomes unbalanced. Since the excitation voltage is constant, a corresponding balance voltage is generated at the signal terminal.
Measurement principle:
The sensor signal processor, through low-pass filtering, amplification, and analog-to-digital conversion, transforms the raw voltage signal into a measurable standard analog signal or a computational digital signal.
Outlet hole: The protection of the outlet hole indicates the quality of the sensor cable. If it is a high-quality cable that is resistant to breakage, there is no need to add a protective device, as it will affect the strain of the elastic body.
