To select a weighing sensor appropriately, a specific measurement task must first consider the principle of the sensor to be used, which requires analysis of multiple factors before a decision can be made.
1. Determine the sensor type based on the object being measured and the measurement environment.
To perform a specific measurement, the first step is to consider which sensor principle to use. This requires analyzing various factors. Even when measuring the same physical quantity, there are multiple sensor principles available. Determining the most suitable sensor principle depends on the characteristics of the measured quantity and the sensor's operating conditions, considering the following specific issues: the measurement range; the sensor size requirements at the measurement location; whether the measurement method is contact or non-contact; the signal extraction method (wired or non-contact); and the sensor's origin (domestic or imported, affordability, or in-house development).
After considering the above issues, you can determine which type of sensor to choose, and then consider the specific performance indicators of the sensor.
2. Sensitivity Selection
Generally, within the linear range of a sensor, higher sensitivity is desirable. This is because only with high sensitivity can the output signal corresponding to changes in the measured quantity be relatively large, which is beneficial for signal processing. However, it should be noted that high sensor sensitivity also makes it easier for external noise unrelated to the measured quantity to enter the sensor and be amplified by the amplification system, affecting measurement accuracy. Therefore, the sensor itself should have a high signal-to-noise ratio to minimize interference signals introduced from the outside.
Sensor sensitivity is directional. When the measured quantity is a single vector and its directionality is critical, a sensor with low sensitivity in other directions should be selected; if the measured quantity is a multi-dimensional vector, the lower the cross-sensitivity of the sensor, the better.
3. Frequency response characteristics
The frequency response characteristics of a sensor determine the frequency range of the measurement. It is necessary to maintain distortion-free measurement conditions within the allowable frequency range. In reality, the response of a sensor always has a certain delay, and it is desirable to minimize the delay time.
A sensor with a high frequency response can measure a wide range of signal frequencies. However, due to the influence of structural characteristics, mechanical systems have greater inertia, resulting in sensors with low frequencies being able to measure signals with lower frequencies.
In dynamic measurements, the response characteristics of the signal (steady-state, transient, random, etc.) should be considered to avoid excessive errors.
4. Linear range
The linear range of a sensor refers to the range within which the output is proportional to the input. Theoretically, within this range, the sensitivity remains constant. The wider the linear range of a sensor, the larger its measurement range and the better it guarantees a certain level of measurement accuracy. When selecting a sensor, once the type of sensor is determined, the first thing to consider is whether its measurement range meets the requirements.
However, in reality, no sensor can guarantee linearity; its linearity is relative. When the required measurement accuracy is relatively low, within a certain range, a sensor with small nonlinear errors can be approximated as linear, which greatly simplifies the measurement process.
5. Stability
The ability of a sensor to maintain its performance unchanged after a period of use is called stability. Besides the sensor's own structure, the main factor affecting the long-term stability of a sensor is its operating environment. Therefore, for a sensor to have good stability, it must have strong environmental adaptability.
6. Accuracy
Accuracy is a crucial performance indicator for sensors, and it's a vital factor affecting the overall measurement accuracy of a measurement system. Higher accuracy sensors are generally more expensive. Therefore, a sensor's accuracy only needs to meet the overall accuracy requirements of the measurement system; it's unnecessary to choose an excessively high-accuracy one. This allows for the selection of a cheaper and simpler sensor from among many options that meet the same measurement purpose.
If the measurement purpose is qualitative analysis, a sensor with high repeatability is sufficient, but a sensor with high absolute accuracy is not recommended. If the purpose is quantitative analysis and precise measurement values are required, a sensor with an accuracy class that meets the requirements must be selected.
For certain special applications where a suitable sensor cannot be selected, it is necessary to design and manufacture the sensor in-house. The performance of the self-made sensor should meet the application requirements.
