General rule update time for load cell selection

In the electronic weighing instrument, what kind of weighing sensor is used should be comprehensively measured. In the following, the structure, the range, and the accuracy level of the load cell are described in terms of general considerations.

First, the choice of structure and form

Which type of structure is used for the load cell, mainly depends on the structure of the instrument and the environmental conditions used. If you want to make low-profile scales, you should generally use cantilever beam and spoke type sensors. If the height requirements are not strict, you can use column sensors. In addition, if the environment used by the instrument is very humid and there is a lot of dust, the sealing form should be better; if there is danger of explosion, the intrinsically safe sensor should be used; if it is in the elevated weighing system, it should be considered. Safety and overload protection; if used in high temperature environment, the load cell with water cooling jacket should be used; if it is used in high and cold areas, the sensor with heating device should be considered. In the choice of form, one factor to consider is whether the maintenance is convenient or not and the cost required, that is, once the weighing system is out of order, the repair device can be obtained smoothly and quickly. If you can't do it, it means that the form selection is not suitable.

Second, the choice of range

The closer the weighing value of the weighing system is to the rated capacity of the sensor, the higher the weighing accuracy is. However, in actual use, due to the weight, tare and vibration, impact, and eccentric load of the scale body, it is different. The principle that the measurement system uses the sensor's limit is very different. As a general rule, there may be: * Single sensor static weighing system: fixed load (weighing platform, container, etc.) + variable load (load to be weighed) ≤ rated load of selected sensor X70% * multi-sensor static weighing system : Fixed load (weighing platform, container, etc.) + variable load (load to be weighed) ≤ sensor rated load X number of sensors X70%

70% of the coefficients are added in consideration of vibration, shock, and eccentric load.

It should be noted that: First, the rated capacity of the sensor should be selected to meet the value of the manufacturer's standard product series. Otherwise, non-standard products are selected, which are not only expensive but also difficult to replace after damage. Secondly, in the same weighing system, sensors with different rated capacities are not allowed. Otherwise, the system cannot work normally. Furthermore, the so-called variable load (the load to be weighed) refers to the actual load applied to the sensor. If the force value is transmitted from the weighing platform to the sensor, there is a mechanism for multiplying and attenuating (such as a lever system). Then the impact should be considered.

Third, the choice of accuracy

The accuracy level of the load cell should be selected to meet the accuracy level of the weighing system, as long as it meets this requirement. That is, if the 2500-division sensor can meet the requirements, do not use 3000-division. If several identical forms are used in a weighing system and the sensors of the same rated capacity are operated in parallel, the combined error is Δ, then:

Δ=Δ/n1/2 (2-12)

Where: Δ: the combined error of a single sensor; n: the number of sensors. In addition, electronic weighing systems generally consist of three major components, they are weighing sensors, weighing displays and mechanical structural components. When the tolerance of the system is 1, the integrated error (Δ) of the load cell, which is one of the main components of the non-automatic weighing instrument, can only reach a proportional component of 0.7. According to this and the formula (2--12), it is not difficult to make a choice of the required sensor accuracy.

Fourth, how should some special requirements be achieved?

In some weighing systems, there may be some special requirements. For example, in the railway scale, it is desirable that the load cell has a smaller amount of elastic deformation, so that the weighing platform can be reduced in weight during weighing, so that the truck is driving. Reduce shock and vibration when entering and exiting the weighing platform. In addition, when constructing a dynamic weighing system, it is inevitable to consider the natural frequency of the load cell used, and whether it can meet the requirements of dynamic measurement. These parameters are not listed in the general product introduction. Therefore, when you want to understand these technical parameters, you should consult the manufacturer to avoid mistakes.