Generally the pressure measuring instrument electrical measuring instrument called a pressure sensor (pressuretransducer). It is the pressure sensor signal into a voltage signal output. Typically the pressure sensor is generally sensitive element and an elastic displacement of the sensitive elements. The elastic element is sensitive so that the measured pressure acts on the area and converted into a displacement or strain sensitive elements and by the displacement or strain gauge pressure is converted into an electrical signal into a certain relation. Sometimes these two kinds of functional elements in one set. Application: First, for detecting air pressure, comprising an intake vacuum, atmospheric pressure, air pressure and tire air pressure within the cylinder; the second is detecting a hydraulic pressure, comprising a hydraulic transmission, brake and hydraulic suspension oil pressure.
1. How corrosion characteristics of the pressure sensor
1. The medium, how conductive. The selection of the appropriate type of sensor such media attributes.
2. How the medium temperature range, the temperature range is often one of many media, according to this information to select the range of the compensation temperature sensor consistent with, the second is the maximum temperature range of the medium, the rootAccordingly Select sensor consistent temperature range.
3. If the above two points, if not selected properly, most likely damage the sensor or even cause accidents.
2. The pressure sensor Category
Type
more pressure sensors, the current commonly used pressure sensors and piezoresistive pressure sensors piezo two kinds.
1. The piezoresistive pressure sensor
piezoresistive pressure sensor working principle is that when the pressure generating varistor resistance change, amplified by an amplifier and standard pressure calibration can pressure testing. Piezoresistive pressure sensor performance depends primarily on the pressure-sensitive element (i.e., a varistor), an amplifier circuit, and the production process of calibration and aging.
piezoresistive sensors are integrated circuit process technology, producing a sheet resistance of the four equivalent on a silicon wafer, and form a bridge circuit. When the force is not, the bridge is in equilibrium, no voltage output; when subject to force, the bridge out of balance voltage, the output is proportional to stress. Piezoresistive sensor works with the traditional operating principle of the semiconductor strain sensor, it is based on the piezoresistive effect of a semiconductor material.
2. The piezoelectric pressure transducer
Based on the principle of piezoelectric pressure sensor piezoelectric effect. Some piezoelectric effect of the dielectric is deformed by an external force in a certain direction, the internal polarization is generated, while the opposite positive and negative charges appear on its two opposite surfaces. When the external force is removed, it will return to the uncharged state, a phenomenon known asPiezoelectric effect.
When changing the direction of the force, the polarity of the charge has changed. In contrast, when the electric field is applied in the direction of polarization of the dielectric, the dielectric will be deformed, the electric field is removed, the deformation of the dielectric disappear, this phenomenon is called the inverse piezoelectric effect. The piezoelectric pressure sensor type and model range according to the form of the resilient element and the force sensitive receiving means can be divided into two types of piston and diaphragm. Diaphragm mainly by the body, the diaphragm and the piezoelectric elements. The piezoelectric element is supported on the body, transmitting the measured pressure from the diaphragm to the piezoelectric element, and then into an electrical signal by the piezoelectric element a certain relationship with the measured output pressure.
Characteristics of such a sensor is small, and good dynamic characteristics, such as high temperature. Modern measuring technology an ever-increasing demands on the performance of the sensor. Piezoelectric material most suitable for the development of such a pressure sensor. Quartz is a very good piezoelectric material, the piezoelectric effect is found on top of it. Currently more effective way is to choose quartz crystal cutting method suitable for high temperature conditions.
3. The pressure sensor Fault
1. The transmitter and the gauge pointer is large control deviations. Deviation is normal, the normal range of deviation can be confirmed;
2. Pressure up, the transmitter sends falters. When this happens, the pressure should first check whether the interface is blocked or leak, if not confirmed, checking and checking the power wiring, such as the power supply is normal, the output to see if a simple pressure change, or view the sensor output whether there is zero position, if there is no change in the sensor is damaged, the instrument may be damaged or the whole system the other ringProblems section;
3. The pressure transmitter output does not change, then the pressure transmitter output changes abruptly, go back to zero relief transmitter, most likely a pressure sensor ring The problem.
Since the sealing ring is common specifications reason, after tightening the sensor ring is compressed to the pressure sensor lead clogging sensor inside the mouth, the pressure medium is pressurized entrance, but in the pressure suddenly flung ring , the pressure sensor is subjected to a pressure change. Exclude the preferred method is to remove the sensor failure, direct visualization zero position is normal, if normal zero again replaceable seals;
4. The transmitter output signal unstable. This failure is willing to have a problem pressure source. A pressure source itself is an unstable pressure, most likely interference meter or a pressure sensor is not strong, vibration sensor itself is very powerful and sensor fault;
The mounting position of the differential pressure transmitter effects of zero output. Since the differential pressure transmitter measurement range is very small, the sensing element can affect transmitter output differential pressure transmitter.
4. The main performance parameters of the pressure sensor
1. The damage to the pressure
refers to damage to the pressure sensor can be processed without damage to the housing or the sensor element on the sensor maximum pressure.
2. The set pressure range
set pressure range is a pressure range to meet the predetermined standard value. That is between the maximum and minimum temperatures, pressure range of the sensor output in line with the provisions of the operating characteristics. In practice the pressure measured by sensorWithin this range.
3. Maximum Pressure range
The maximum pressure is the maximum pressure range of the sensor can withstand a long time, without causing a permanent change in the output characteristics. A semiconductor pressure sensor in particular, to improve the linearity and temperature characteristics, are generally set pressure range is greatly reduced. Thus, continuous use will not be damaged even above the rated pressure. The maximum pressure is generally 2-3 times the rated pressure of the highest value.
4. linearity
refers to a linearity within the operating pressure range, the maximum deviation from the linear relationship between sensor output and the pressure. Temperature range
5. Temperature range
a pressure sensor into the compensation temperature range and operating temperature range. Compensation temperature range due to the application of the temperature compensation accuracy within the temperature range into the nominal range. Operating temperature range of guaranteed temperature range of the pressure sensor can work properly.
6. Pressure Hysteresis
at room temperature is within the working pressure range, the pressure approaches a minimum operating pressure and a maximum operating pressure, the difference between the sensor output.