How to choose a sensor - Solutions - Huaqiang Electronic Network

Modern sensors come in a wide variety of principles and structures. Choosing the right sensor for a specific measurement purpose, object, and environment is the first key challenge when conducting any measurement task. Once the sensor is selected, the appropriate measurement method and equipment can be determined. The success of the entire measurement process largely depends on whether the sensor has been chosen correctly.

1. Determine the type of sensor based on the measurement object and environment.

To begin a specific measurement task, it's essential to understand the sensor’s principle. This requires careful analysis of various factors. Even when measuring the same physical quantity, there are many sensor types available. Which one is most suitable depends on several considerations: the range size, the position of the measured point relative to the sensor, whether the measurement is contact or non-contact, how the signal is extracted (wired or wireless), the source of the sensor (domestic or imported), cost, and whether it's self-developed.

After evaluating these aspects, you can determine the general type of sensor, and then focus on its specific performance characteristics.

2. Sensitivity Selection

In the linear operating range of a sensor, higher sensitivity is generally preferred. A high sensitivity means that the output signal corresponding to a small change in the measured value will be larger, which makes signal processing easier. However, it's important to note that high sensitivity also makes the sensor more susceptible to external noise, which can be amplified by the system and affect measurement accuracy. Therefore, the sensor should have a good signal-to-noise ratio, and external disturbances should be minimized as much as possible.

Sensitivity is directional. If the measurement involves a single vector with strict directionality, choose a sensor with lower sensitivity. For multi-dimensional measurements, cross-sensitivity should be as low as possible.

3. Frequency Response Characteristics

The frequency response of a sensor determines the range of frequencies it can measure. The system must maintain distortion-free operation within the allowable frequency range. In reality, all sensors have some delay, and shorter delays are better.

A higher frequency response allows the sensor to capture a wider range of signals. Due to structural limitations, mechanical systems often have high inertia, which limits the measurable frequency of low-frequency sensors.

In dynamic measurements, the sensor’s response characteristics should match the signal type (steady-state, transient, random, etc.) to avoid over-response errors.

4. Linear Range

The linear range of a sensor refers to the input range where the output is proportional to the input. Within this range, the sensitivity remains constant. A wider linear range means greater measurement capability and higher accuracy. When selecting a sensor, after determining the type, the first thing to check is whether its range meets the requirements.

However, no sensor is perfectly linear. Linearity is always relative. If the required accuracy is not very high, a sensor with minimal non-linear error can be approximated as linear, which simplifies the measurement process significantly.

5. Stability

Stability refers to a sensor’s ability to maintain consistent performance over time. Factors like environmental conditions play a major role in long-term stability, besides the sensor’s internal structure. To ensure good stability, the sensor must be able to adapt well to its working environment.

Before choosing a sensor, it’s important to investigate the environment where it will be used. Selecting an appropriate sensor based on the environment or taking steps to reduce environmental impact is crucial.

Stability can be quantified. After a certain usage period, the sensor should be recalibrated to check if its performance has changed. In applications requiring long-term use without easy replacement or calibration, the sensor must meet stricter stability requirements to perform reliably over time.

6. Accuracy

Accuracy is a critical performance indicator for sensors and plays a key role in the overall accuracy of the measurement system. Higher accuracy usually means higher cost. Therefore, the sensor’s accuracy should only be as high as needed to meet the system’s requirements, avoiding unnecessary expenses.

If the measurement is for qualitative analysis, a sensor with good repeatability may be sufficient, and absolute precision may not be necessary. For quantitative analysis, precise values are required, so a sensor with the appropriate accuracy level should be selected.

In some special cases, if the right sensor isn’t available, custom development may be necessary. The homemade sensor must meet the required performance standards for its intended use.