Sensor common faults and solutions

Common malfunctions
The main failures of pressure sensors are as follows:
The first is that the pressure goes up, and the transmitter can't go up. In this case, first check whether the pressure port is leaking or blocked. If it is not confirmed, check the wiring method and check the power supply. If the power supply is normal, simply pressurize to see if the output changes, or check whether there is an output at the zero position of the sensor. If there is no change, the sensor is damaged, which may be caused by damage to the instrument or other links in the entire system;
The second is that the output of the pressurized transmitter does not change, and the output of the re-pressurized transmitter changes suddenly, and the zero position of the pressure release transmitter cannot be returned, which is likely to be a problem with the pressure sensor seal. Commonly, due to the specifications of the sealing ring, after the sensor is tightened, the sealing ring is compressed into the pressure port of the sensor to block the sensor. When pressurized, the pressure medium cannot enter, but when the pressure is high, the sealing ring is suddenly opened, and the pressure sensor is under pressure. Variety. The best way to troubleshoot this kind of failure is to remove the sensor and directly check whether the zero position is normal. If the zero position is normal, replace the sealing ring and try again;
The third is that the output signal of the transmitter is unstable. It is possible that this failure is a stressor problem. The pressure source itself is an unstable pressure, which is likely to be due to the weak anti-interference ability of the instrument or pressure sensor, the vibration of the sensor itself and the failure of the sensor; the fourth is the large deviation between the transmitter and the pointer pressure gauge. Deviation is a normal phenomenon, just confirm the normal deviation range;
The last type of failure that is prone to occur is the influence of the installation position of the differential pressure transmitter on the zero output. Due to the small measurement range of the differential pressure transmitter, the sensing element in the transmitter will affect the output of the differential pressure transmitter. When installing, the axis of the pressure sensitive part of the transmitter should be perpendicular to the direction of gravity. After installation and fixing, adjust the zero position of the transmitter to the standard value.
zero drift
The main reasons for the zero point drift of the pressure sensor are as follows:
1. There are bubbles or impurities in the rubber layer of the strain gauge
2. The performance of the strain gauge itself is unstable
3. There are virtual solder joints in the circuit
4. The stress release of the elastic body is not complete; in addition, it is also related to the magnetic field, frequency, temperature and many other things. Electric drift or some drift will exist, but we can reduce its scope or correct it in some ways.
Zero-point thermal drift is an important indicator that affects the performance of pressure sensors and has been widely valued. Internationally, it is believed that the zero-point thermal drift depends only on the inequalities of the force-sensitive resistors and its temperature nonlinearity. In fact, the zero-point thermal drift is also related to the reverse leakage of the force-sensitive resistors. In this regard, polysilicon can absorb heavy metal impurities in the substrate, thereby reducing the reverse leakage of the force sensitive resistor, improving the zero-point thermal drift, and improving the performance of the sensor.
What are the other ways to reduce and correct the electrical drift? What are the important effects of the zero-point electrical drift besides affecting the measurement accuracy and reducing the sensitivity of the pressure sensor?
The thermal zero drift of the pressure sensor can be eliminated by using the zero point electrical drift. The so-called zero point drift refers to the phenomenon that when the input terminal of the amplifier is short-circuited, there is an irregular and slowly changing voltage at the input terminal. The main reason for zero drift is the influence of temperature changes on transistor parameters and fluctuations in power supply voltage. In most amplifiers, the zero drift of the front stage has the greatest impact. The more stages and the greater the magnification, the more serious the zero drift .
The size of the drift mainly depends on the selection of the strain material, and the structure or composition of the material determines its stability or thermal sensitivity.
The processing of the selected material is also very important. Different processes will produce strain values with different effects. The key lies in the stability or regular changes of the bridge value after some adjustments such as aging.
There are many drift adjustment methods, most of which are determined according to the manufacturer's conditions or production needs. Most manufacturers have a good control over the zero drift. Temperature adjustment can be compensated, aging, etc. through internal temperature resistance and heating zero-sensitivity resistance.
For transformers using circuit conversion, the drift of the circuit part can be compensated by selecting good components and designing more suitable circuits.
The strain material should choose the material with high sensitivity coefficient and small temperature change.
Fault detection
Check the faults on the construction site, most of them are caused by the improper use and installation of pressure sensors, and there are several aspects to sum up.
1. The primary components (orifice plate, remote measurement joint, etc.) are blocked or the installation form is wrong, and the pressure point is unreasonable.
2. The pressure induction tube leaks or is blocked, there is residual gas in the liquid filling tube or residual liquid in the gas charging tube, and there are deposits in the process flange of the transmitter, forming a measurement dead zone.
3. The wiring of the transmitter is incorrect, the power supply voltage is too high or too low, and the connection between the indicator meter and the instrument terminal is not in good contact.
4. The installation is not strictly in accordance with the technical requirements, and the installation method and site environment do not meet the technical requirements.