The influence of temperature on weight sensors

The influence of temperature on weight sensors

With the continuous development of intelligent manufacturing, the use of weighing systems in various industries is gradually increasing. However, when using weighing, a problem will be found. After installing the weighing system, even if there is no material, the displayed weight will vary with the time of day. The larger the division value is set, the more obvious this phenomenon becomes. So why does this problem occur?
According to the constantly changing environmental temperature in the usage scenario of the weighing sensor, the weighing system will also produce a certain temperature drift. When we choose the weighing sensor, the technical parameters column will list the temperature compensation range, working temperature range, sensitivity temperature coefficient, and zero temperature coefficient. Within the rated temperature range, it should not exceed the single or cumulative error listed in the technical parameter table. The temperature range is used to define the temperature limit of the weighing sensor for measuring functions and not being damaged, which means that some errors may exceed the data in the technical parameter table. The storage temperature range is also indicated in the technical parameter table.
The reasons why temperature affects sensors:
The impact of temperature on sensors mainly consists of two parts: the zero temperature coefficient and the sensitivity temperature coefficient.

So how is the zero temperature coefficient generated? When making a weighing sensor, it is necessary to stick the strain gauges one by one onto the elastic body. The strain gauges generally consist of a base and a wire grid, and a patch adhesive is also used during the bonding process. Non outdated substrates, wire grids, patch adhesives, and elastomers all have a common characteristic: thermal expansion and contraction, that is, expansion when heated and contraction when cooled; And these materials also have different sizes of expansion and contraction according to temperature changes; On the other hand, since the strain gauge wire grid is made of a resistive material, the resistivity also changes with temperature. So when they are combined together, the resistance value of the strain gauge will also change with temperature changes; Due to the extensive manual labor involved in the production of strain gauges and sensors, each strain gauge on the same sensor exhibits different resistance changes. These changes are then combined into a zero point output through a detection circuit. At this point, the zero point output has already become a function of temperature, constantly changing with temperature.
The reason for the generation of sensitivity temperature coefficient is also due to the attachment of strain gauges to elastic bodies. Research has shown that the sensitivity coefficient of strain gauges varies with changes in ambient temperature. That is to say, although a strain gauge senses the same strain at different temperatures, the magnitude of the resistance change it produces is different; In addition, elastomers are generally made of metal materials, and metal materials also have an important parameter, which is their elastic modulus E. It is a parameter that describes the magnitude of deformation of metal materials under stress. Research has shown that the elastic modulus changes under the influence of temperature and generally decreases with increasing temperature. This causes the weighing sensor to deform with the increase of environmental temperature without any change in the external force it is subjected to. When combined with the change in the sensitivity coefficient of the strain gauge, the output of the sensor will increase. This increase is known as the sensitivity temperature coefficient of the weighing sensor, which increases with the increase of environmental temperature.

So now that we know the reasons why temperature affects sensors, how can we improve it?

To improve the impact of temperature on sensors, manufacturers need to compensate for the zero temperature coefficient and sensitivity temperature during production; Another prerequisite for compensation is that we first need to measure their values before we can proceed with compensation. When sensors are produced in large quantities, the dispersion of their zero temperature characteristics is still very large, so it is not possible to compensate each sensor with a unified compensation parameter. Only each sensor can be compensated separately and then tested one by one before compensation. This production efficiency is relatively low, and temperature testing needs to be completed under different environmental conditions. To complete this task, it is necessary to first prepare a large environmental laboratory, where the internal temperature can be adjusted freely between -10 ℃ and 40 ℃, and there is only a very small temperature difference at different positions in the greenhouse, and the accuracy of the temperature should be quite high; Only through continuous compensation and testing can the stability of the weighing sensor be ensured after it is deployed.

Generally speaking, the method of testing is to use high and low temperature compensation boxes. However, due to the expensive price of this equipment, many companies hesitate and can only conduct various tests outside. Yunlang Sensing has several high and low temperature test boxes in the production process to ensure that the temperature impact of the weighing sensor is reduced during production.