The wide application of the miniature pressure sensor has given many people a certain understanding of it, but this understanding is still not deep enough, only some superficial content is known, and the deeper level needs to be summarized. For example, how to use the miniature pressure sensor and the matters needing attention in the use process. The prerequisite for doing this is to understand the working principle of this miniature pressure sensor. These OFweek Mall will give an overview.
How to use the miniature pressure sensor?
The key point in the process of using the miniature pressure sensor is that the correct installation position of the sensor on the process pipeline is related to the measured medium. Master the correct use of the miniature pressure sensor to obtain the best measurement results!
1. Prevent the sensor from contacting corrosive or overheated media.
2. Prevent dross from depositing in the pipeline.
3. When measuring the liquid pressure, the pressure valve should be opened on the side of the process pipe to avoid precipitation.
4. When measuring gas pressure, the pressure joint should be opened at the top of the process pipe, and the miniature pressure sensor should also be installed on the upper part of the process pipe so that the accumulated liquid can be easily injected into the process pipe.
5. The pressure guiding tube should be installed in a place with small temperature fluctuations.
6. When measuring steam or other high-temperature media, a condenser, such as a buffer tube (coil), should be added. The working temperature of the miniature pressure sensor should not exceed the limit.
The working principle of common miniature pressure sensor
1. Piezoelectric miniature pressure sensor: The piezoelectric effect is the main working principle of the piezoelectric sensor. Piezoelectric sensors cannot be used for static measurements, because the charge after an external force can only be saved when the loop has infinite input impedance. This is not the case, so this confirms that the piezoelectric sensor can only measure dynamic stress.
2. Ceramic miniature pressure sensor: The ceramic miniature pressure sensor is based on the piezoresistive effect. The pressure is directly on the front surface of the ceramic diaphragm, causing small deformation of the diaphragm. The thick film resistor is printed on the back of the ceramic diaphragm and connected to form a benefit. Due to the piezoresistive effect of the varistor, the stone bridge generates a high linear voltage signal proportional to the pressure, and the voltage signal is proportional to the excitation voltage. According to the pressure range, the standard signal is calibrated to 2.0 / 3.0 / 3.3mv. /v, etc., compatible with strain gauge sensors.
3. Diffused silicon miniature pressure sensor: The working principle of diffused silicon miniature pressure sensor is also based on the piezoresistive effect. Using the principle of piezoresistive effect, the pressure of the measured medium directly acts on the diaphragm (stainless steel or ceramic) of the sensor, thereby producing the diaphragm and the medium. The micro-displacement proportional to the pressure changes the resistance value of the sensor, an electronic circuit is used to detect the change, and a standard measurement signal corresponding to the pressure is converted.
Things to pay attention to when using the miniature pressure sensor: when freezing occurs in winter, the sensor installed outdoors should take anti-freezing measures to prevent the pressure inlet liquid from expanding due to the amount of ice and causing damage to the sensor. When measuring liquid pressure, the installation position of the sensor should avoid the impact of the liquid (water hammer phenomenon) to avoid damage to the sensor due to overpressure.
Micro pressure sensor structure. It is composed of a base material, a metal strain wire or strain foil, an insulating protective plate and a lead wire. Depending on the application, the resistance of the strain gauge can be designed by the designer, but the resistance range should be noted: the resistance is too small, the required drive current is too large, and the heat of the strain gauge will cause the temperature to be too high. When used in different environments, the resistance value of the strain gauge changes too much, the output zero drift is obvious, and the zero adjustment circuit is too complicated. The resistance is too high, the impedance is too high, and the ability to resist external electromagnetic interference is poor. Generally speaking, it is about tens of euros to tens of thousands of euros.
What is the role of the miniature pressure sensor? It is mainly to measure pressure, which converts the measured pressure value into a current or voltage signal, which can be output to the secondary instrument, and then the secondary instrument is converted into the corresponding pressure value. An instrument that converts a pressure variable into a transmittable standardized output signal, and has a given continuous function relationship (usually a linear function) between the output signal and the pressure variable.