When selecting sensors for PLC control cabinets, the following core factors need to be considered: measurement object and measurement environment, sensor type, sensitivity, frequency response characteristics, dynamic range, response time, stability, repeatability, reliability, and interface and communication protocol.
First, determine the type of sensor according to the measurement object and the measurement environment. To carry out specific measurement work, we must first consider what principle the sensor uses. This requires analyzing the characteristics of the measured value and the use conditions of the sensor, such as the range, the requirements of the measured position on the sensor volume, whether the measurement method is contact or non-contact, whether the signal extraction method is wired or non-contact measurement, and whether the sensor is domestic or imported.
Secondly, consider the sensitivity of the sensor. Generally, within the linear range of the sensor, the higher the sensitivity, the better, because this is conducive to signal processing. However, high sensitivity is also prone to introduce external noise, so the sensor should have a high signal-to-noise ratio to reduce interference signals.
Frequency response characteristics are also a key factor. The frequency response characteristics of the sensor determine the measurable frequency range, and the measurement conditions must be maintained without distortion within the allowable frequency range. Sensors with high high-frequency response can measure signals in a wide frequency range, but due to the influence of structural characteristics, the inertia of the mechanical system is large, so the selection needs to be considered based on the characteristics of the signal (steady state, transient, random, etc.).
Dynamic range and response time are equally important. The dynamic range depends on the application requirements. For example, a sensor with a high dynamic range is required to read the temperature from a heating furnace. Response time is the time it takes for a sensor to represent the actual measured value and is critical for some PLC automation applications.
Stability, repeatability, and reliability are also factors to consider when selecting a sensor. The stability of a sensor refers to its ability to produce the same output for a given input level over a long period of time, and repeatability refers to its ability to produce the same output for the same input value. Reliability determines the likelihood that the sensor will provide accurate, repeatable readings under predetermined operating conditions.
Finally, consider the sensor’s interface and communication protocol. These factors need to be matched with the PLC control system to ensure system compatibility and stability.
