The working principle and application of capacitive liquid level sensor

Now all kinds of sensors have been applied in many fields, such as refrigerators and air conditioners used in our homes, temperature sensors will be used, and capacitive level sensors will be used on water heaters. Let me talk about the working principle of the capacitive liquid level sensor, where can the capacitive liquid level sensor be applied?

The working principle of capacitive liquid level sensor

Capacitive liquid level sensors use the principle of static electricity. The measurement of this switch is usually one plate that forms the capacitor, and the other plate is the external of the switch. This external measurement process is usually grounded or connected to the machine of the device. When an object moves to the proximity switch, whether it is a conductor or not, due to its proximity, the dielectric constant of the capacitor must be changed, so that the capacitance changes, so that the state of the circuit connected to the measuring head also occurs Changes, which can control the switch on or off. The objects detected by this proximity switch are not limited to conductors, but may be insulating liquid or powder objects and so on.

Application of capacitance level sensor

Capacitive liquid level sensors are widely used in household appliances and industrial automation production. Such as humidifiers, mopping machines, water purifiers, coffee machines, water dispensers, water heaters, automatic feeding production lines, etc. have applications. Capacitive liquid level sensor can also be used in automobiles, it effectively protects the safe driving of the car, but the current domestic capacitive liquid level sensor technology is rarely used in automobiles, capacitive liquid on fuel oil measurement system Position sensors also mainly rely on imports, so the development of domestic capacitive liquid level sensors is imperative.

Finally, take everyone to understand how to choose the sensor

1. Determine the type of sensor according to the measurement object and measurement environment

To carry out a specific measurement work, we must first consider what kind of sensor is used. This needs to be determined after analyzing many factors. Because, even when measuring the same physical quantity, there are multiple principles of sensors available, which principle of the sensor is more suitable, you need to consider the following specific issues according to the characteristics of the measured and the sensor’s use conditions: the size of the range; The requirements of the measured position on the volume of the sensor; whether the measurement method is contact or non-contact; the signal extraction method, wired or non-contact measurement; the source of the sensor, whether it is domestic or imported, whether the price can bear, or developed by itself. After considering the above problems, you can determine which type of sensor to choose, and then consider the specific performance indicators of the sensor.

2. Sensor frequency response characteristics

The frequency response characteristic of the hardware sensor determines the frequency range to be measured, and the measurement conditions must be maintained within the allowable frequency range without distortion. In fact, the sensor response always has a certain delay. I hope the shorter the delay time, the better. The frequency response of the sensor is high, and the frequency range of the measurable signal is wide. However, due to the influence of structural characteristics, the inertia of the mechanical system is large, and the frequency of the measurable signal is low because of the low frequency sensor. In the dynamic measurement, the response characteristics should be based on the characteristics of the signal (steady state, transient, random, etc.), so as to avoid excessive fire errors.

3. Selection of sensor sensitivity

Generally, in the linear range of the sensor, the higher the sensitivity of the sensor, the better. Because only when the sensitivity is high, the value of the output signal corresponding to the measured change is relatively large, which is conducive to signal processing. However, it should be noted that the sensitivity of the sensor is high, and external noise that is not related to the measurement is also easily mixed in, and it will also be amplified by the amplification system, affecting the measurement accuracy. Therefore, it is required that the sensor itself should have a high signal-to-noise ratio, so as to reduce the factory disturbance signals introduced from the outside. The sensitivity of the sensor is directional. When the measured value is a single vector and the directionality is high, you should choose a sensor with low sensitivity in other directions. If the measured value is a multidimensional vector, the smaller the cross-sensitivity of the sensor, the better.

4. Sensor stability

After a sensor is used for a period of time, its ability to keep its performance unchanged is called stability. In addition to the structure of the sensor itself, the factors that affect the long-term stability of the sensor are mainly the environment in which the sensor is used. Therefore, to make the sensor have good stability, the sensor must have a strong ability to adapt to the environment.

Before selecting a sensor, the environment in which it is used should be investigated, and the appropriate sensor should be selected according to the specific use environment, or appropriate measures should be taken to reduce the environmental impact

There are quantitative indicators for the stability of the sensor. After the period of use is exceeded, the calibration should be re-calibrated before use to determine whether the performance of the sensor has changed. In some occasions where the sensor can be used for a long time and cannot be easily replaced or calibrated, the stability of the selected sensor is more stringent, and it must be able to withstand the test for a long time.

5. Sensor linear range

The linear range of the sensor refers to the range in which the output is proportional to the input. In theory, within this range, the sensitivity remains constant. The wider the linear range of the sensor, the larger the range, and it can ensure a certain measurement accuracy. When selecting a sensor, when the type of sensor is determined, it is first necessary to see whether its range meets the requirements. But in fact, no sensor can guarantee absolute linearity, and its linearity is also relative. When the required measurement accuracy is relatively low, within a certain range, the sensor with small nonlinear error can be regarded as linear, which will bring great convenience to the measurement.

Post time: Jul-13-2020