1. Selection of accuracy

Accuracy is a crucial performance indicator of sensors, serving as a vital link in determining the measurement accuracy of the entire measurement system. The higher the accuracy of a sensor, the more expensive it tends to be. Therefore, it is sufficient for the sensor's accuracy to meet the requirements of the entire measurement system, rather than being excessively high. This approach allows for the selection of cheaper and simpler sensors among various options that serve the same measurement purpose. If the measurement purpose is qualitative analysis, a sensor with high repeatability accuracy is preferred over one with high absolute value accuracy. If quantitative analysis is required to obtain precise measurement values, a sensor with an appropriate accuracy level should be chosen.

 The accuracy selection meets the following two conditions:

 1. Meet the requirements for instrument input. The output signal of the sensor must be greater than or equal to the input signal required by the instrument.

 2. Meet the accuracy requirements of the entire electronic scale. An electronic scale is mainly composed of three parts: the scale body, sensor, and instrument. When selecting the accuracy of the sensor, it should be slightly higher than the theoretical calculation value.

 II. Selection of sensor quantity and range

 The selection of the number of sensors is determined based on the purpose of the electronic weighing apparatus and the number of points the scale body needs to be supported at (the number of support points should be determined according to the principle of making the geometric center of gravity of the scale body coincide with its actual center of gravity).

The selection of sensor range can be determined based on a comprehensive evaluation of factors such as the scale's maximum weighing value, the number of sensors selected, the self-weight of the scale body, the maximum possible eccentric load, and dynamic load. According to experience, sensors should generally operate within 30% to 70% of their range. However, for weighing instruments with significant impact forces, sensors should generally operate within 20% to 30% of their range to ensure their safe use and longevity.

 III. Selection of sensitivity

Generally, within the linear range of a sensor, it is desirable to have the highest sensitivity possible. This is because only when the sensitivity is high, the output signal value corresponding to the measured quantity is relatively large, which is beneficial for signal processing. However, when the sensitivity is high, external noise unrelated to the measured quantity will also be amplified by the amplification system, affecting measurement accuracy. Therefore, it is required that the sensor itself should have a high signal-to-noise ratio to minimize the interference signals introduced from the outside.

 IV. Selection of Stability

The ability of a sensor to maintain its performance after being used for a period of time is called stability. Apart from its own structure, the main factor affecting the long-term stability of a sensor is the usage environment. Therefore, for a sensor to have good stability, it must have strong environmental adaptability. Before selecting a sensor, it is necessary to investigate its usage environment and choose a suitable sensor based on the specific usage environment, or take appropriate measures to reduce the impact of the environment.

 Environmental factors can have the following impacts on load cells:

 1. High temperature environment causes the coating material of the sensor to melt, the solder joints to melt, and the internal stress of the elastic body to undergo structural changes.

 2. The open-air dust and humidity may cause short circuits to the sensor.

 3. In highly corrosive environments, such as humidity and acidity, the sensor may suffer from damage to the elastomer or short circuiting.

 4. The influence of electromagnetic fields on the output of chaotic signals from sensors.

 5. Special explosion-proof sensors must be used in flammable and explosive environments.

 The stability of sensors has quantitative indicators. After exceeding the usage period, sensors should be recalibrated before use to determine whether their performance has changed. In some situations where sensors are required to be used for a long time and cannot be easily replaced or recalibrated, the stability requirements for the selected sensors are more stringent, and they must withstand long-term testing.