The lag error is usually defined as the difference between the load cell process (input increase) and the return load (input decrease) output measurement for the same external load value. In other words, corresponding to the same size of the input signal, weighing the size of the output signal of the positive and negative stroke of the sensor
They're not equal. That's the lag error. The lag error loop of most load cells is usually cigar-shaped, and the width of the loop is determined by the load
The magnitude of the cycle is determined. When measuring hysteresis, there are always some effects of creep and creep recovery, so the hysteresis test is required
In a very short time.
The hysteresis error of load cell is related to the structure and heat treatment process of elastic element, the thickness of resistance strain gauge base and strain adhesive layer
There is a great relationship, summed up to affect the lag error of the main factors are:
(1) The design of the contact surface between the bearing surface of the elastic element and the lower pressure pad is unreasonable, mainly because the contact area is too large and the friction coefficient of the pressure pad material is large
Let's wait. When the elastic element is loaded, the bottom surface will inevitably produce an outward moving torque. When the load is removed, due to the existence of friction torque on the bottom surface,
The backward-facing torque is smaller than the outward-moving torque, which retards the recovery of elastic element deformation and causes hysteresis error.
(2) The design of the elastic element strain zone and supporting boundary is unreasonable, and the inherent lag is large, and the more typical structure is the spoke type weighing transmission
The sensillum. The deformation displacement of the tire is closely related to its stiffness. The stiffness is large, the deformation displacement is small, the bottom friction action time is short, and the spoke strain recovery is fast.
The lag is small, and vice versa, the lag is large. Therefore, the stiffness of the wheel hub and tire should be large enough to ensure that the Angle of the joint between the wheel spoke and the wheel hub and tire is zero.
(3) The boundary condition of the double-shear beam type weighing sensor has a great influence on the hysteresis, and the contact surface between the elastic element of the double-shear beam and the base slides
It is an important cause of lag error. In the process of loading and unloading, the elastic element of the double shear beam is opposite to the sliding direction of the base, so it acts
The direction of the friction force on the elastic element is also opposite, and it is this friction force that causes the change of shear stress in the strain region. The friction coefficient of the contact surface is large
The absolute value of hysteresis increases from small to large as the load increases. The distance between the center of the blind hole and the end face of the elastic element is too small, and the friction force will affect the strain zone
The influence is also larger.
(4) The influence of machining form and position tolerance is prominent in the ring type and plate ring type elastic elements, when the threads are loaded at both ends
When the elastic element is concentric, the real load value through the elastic element is α Angle with the measurement axis, and the α Angle gradually becomes smaller with the increase of the load
A parabola in which the output increases as the load increases. After unloading, each connector does not return to the initial position, resulting in hysteresis error.
(5) The protective shell and sealing diaphragm on the elastic element of the weighing sensor should be reasonably designed as far as possible not to affect the sensitivity. If any is incorrect
Contact or subjected to a certain stress will produce a force or moment that blocks the recovery of elastic element deformation, resulting in hysteresis error.
(6) Reasonable selection of heat treatment process of elastic element metal materials to reduce the elastic hysteresis of the material itself. For example, the most widely used
The elastic hysteresis of alloy steel 40CrNiM0A is related to its microstructure, and different tempering temperatures get different metallographic microstructure, there is no
With the same elastic hysteresis, the maximum value can reach 0.11%.