Zero thermal drift is an important indicator affecting the performance of pressure sensors and has received extensive attention. Internationally, the zero thermal drift is only dependent on the inequality of the force-sensitive resistor and its temperature nonlinearity. In fact, the zero thermal drift is also related to the reverse leakage of the force-sensitive resistor. At this point, 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 the electric drift and correct the electric drift? What are the important effects of the zero point electric drift in addition to the measurement accuracy and sensitivity of the pressure sensor?
The zero-point electric drift can eliminate the thermal zero drift of the pressure sensor. The so-called zero-point drift refers to the phenomenon that when the input end of the amplifier is short-circuited, there is an irregular and slowly changing voltage at the input end. The main cause of zero drift is the influence of temperature change on the transistor parameters and the fluctuation of the power supply voltage. In most amplifiers, the zero drift of the front stage has the greatest influence. The more the number of stages and the larger the amplification factor, the more serious the zero drift. .
The size of the drift is mainly due to the choice of the strain material, and the structure or composition of the material determines its stability or heat sensitivity.
It is also very important to make the processing after the material is selected. The process is different, and the strain value of different effects will be produced. The key point is the stability of the bridge value or the change of the process law after adjustment by some aging.
There are many adjustment methods for drift, most of which are determined according to the manufacturer's conditions or production requirements. Most manufacturers control the zero drift very well. Temperature regulation can be compensated, aging, etc. by internal temperature resistance and heating zero sensitivity resistor.
For transformers with circuit conversion, the drift of the circuit can be compensated by selecting good components and designing more suitable circuits.
Pressure transmitter common faults:
1. The pressure goes up:
If the transmitter is not connected, 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 is normal, simply pressurize to see if the output changes, or check the sensor zero. Whether the bit has an output, if there is no change, the sensor is damaged, which may be a problem of instrument damage or other parts of the whole system;
2. The pressure transmitter output does not change:
The output of the re-pressurized transmitter suddenly changes, and the pressure-receiving transmitter can't go back to zero. It is very likely that the pressure sensor seal is a problem. It is common for the seal ring specification. After the sensor is tightened, the seal ring is compressed into the sensor pressure port to block the sensor. When the pressure is applied, the pressure medium can not enter, but when the pressure is high, the seal ring is suddenly opened, and the pressure sensor is under pressure. Variety.
The best way to eliminate this kind of fault is to remove the sensor and directly check whether the zero position is normal. If the zero position is normal, replace the seal and try again.
3. The output signal of the transmitter is unstable:
This type of failure may be a problem with the pressure source. The pressure source itself is an unstable pressure. It is very likely that the instrument or pressure sensor is not strong in anti-interference ability, the sensor itself is very vibrating and the sensor is faulty. The fourth type is that the transmitter and the pointer type pressure gauge have large deviations. Deviation is a normal phenomenon, and the normal deviation range can be confirmed;
4. 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 elements in the transmitter affect the output of the differential pressure transmitter. The pressure sensitive component of the transmitter should be axially perpendicular to the direction of gravity during installation. After installation and fixing, adjust the transmitter zero to the standard value.
Causes the zero drift of the pressure sensor:
1. The strain gauge rubber layer has bubbles or impurities.
2. Strain gauge itself is unstable
3. There are virtual solder joints in the circuit
4. The stress release of the elastomer is incomplete; in addition, it is related to the magnetic field, frequency, temperature and the like. Electric drift or some drift will exist, but we can narrow it down or fix it in some ways.
5. The transmitter wiring is incorrect. The power supply voltage is too high or too low. The contact between the meter head and the meter terminal is poor.
6. It is not installed in strict accordance with technical requirements. The installation method and on-site environment do not meet the technical requirements.