Is the safety of pressure transmitters important? Many people are concerned about this problem. Pressure transmitters can visually display pressure changes in various process steps, insight into the formation of conditions in products or media processes, and monitor safety trends during production operations. And through automatic interlocking or sensing devices, it has built a fast and reliable security guarantee, which plays an important role in preventing accidents and protecting personal and property safety. It is called a safe "eye".
As one of the safety accessories, the pressure transmitter always guards the door of product safety, personal safety and environmental safety. Especially when used in dangerous places such as production, storage and transportation of explosive, flammable and toxic substances, pressure factors play a key role in preventing the occurrence of catastrophic accidents. Therefore, the contribution of pressure transmitters to safety should not be underestimated.
The pressure transmitter measurement principle is: the process pressure and the reference pressure respectively act on the two ends of the integrated silicon pressure sensitive component, and the differential pressure causes the silicon wafer to be deformed (the displacement is small, only μm level), so that the semiconductor technology on the silicon wafer is used. The resulting fully dynamic Wheatstone bridge outputs an mV-level voltage signal proportional to the pressure driven by an external current source. Due to the excellent strength of the silicon material, the linearity and variation index of the output signal are high. In operation, the pressure transmitter converts the measured physical quantity into a mV-level voltage signal and sends it to a differential amplifier with a high amplification factor that cancels the temperature drift. The amplified signal is converted into a corresponding current signal by voltage and current conversion, and then subjected to nonlinear correction, and finally a standard current voltage signal linearly corresponding to the input pressure is generated.
First, wetted material
What we want to think about is the medium measured by the pressure transmitter. The material of the contact medium of the ordinary pressure transmitter is made of 316 stainless steel. If your medium is not corrosive to 316 stainless steel, then all the pressure changes. The transmitter is suitable for your measurement of the medium pressure.
If your medium is corrosive to 316 stainless steel, then we need to use a chemical seal, which not only can measure the pressure of the medium, but also can effectively block the contact between the medium and the pressure transmitter. To maintain the pressure transmitter, the life surface of the pressure transmitter is extended.
Second, the accuracy level
Each type of electronic measuring instrument will have accuracy error, but because the accuracy level of each country is different, for example, the accuracy of the national scales of China and the United States is the better linearity of the sensor, that is, we usually The accuracy of the measurement field is between 10% and 90%; the accuracy of the European standard is the part with poor linearity, which is what we usually call 0 to 10% and 90% to 100% of the measurement. The accuracy of the standard. If the accuracy of the European standard is 1%, the accuracy of the standard in China is 0.5%. The accuracy of the pressure transmitter developed by Huaheng Instrument is 0.2
Third, the range field
The largest area of common sensor measurement is 70% of the sensor's full scale, which is now measuring 70bar pressure. The range of our selected pressure transmitter should be 100bar.
Fourth, the input signal
At present, due to the demand of various types of collection, there are many kinds of input signals of pressure transmitters on the market today, such as 4~20mA, 0~20mA, 0~10V, 0~5V, etc., but the commonly used ones are 4~20mA and 0~10V two kinds. Among the input signals I mentioned below, only 4~20mA is two-wire system (we say that the input is several lines without grounding or shielding), and the others are three-wire system.
Fifth, the medium temperature
Since the signal of the pressure transmitter is locally converted by the electronic circuit, under normal conditions, the temperature of the pressure transmitter is -30 to +100 degrees. If the temperature is too high, we usually use the condensation bend. Cooling the medium, this will definitely make the cost of the manufacturer's special low-temperature pressure transmitter to be much lower.
Sixth, measuring medium
Normally we measure the fluid that is absolutely clean. We can use the standard pressure transmitter indirectly. If the medium you are measuring is crystallized or thin, we usually use external diaphragm or Used in conjunction with a chemical seal, this will effectively block the media from blocking the pressure measuring orifice.
After confirming the following five parameters, we must also confirm the process connection interface of your pressure transmitter and the supply voltage of the pressure transmitter; if you use it in a special place, you should think about explosion protection and protection level.
Pressure transmitters are prone to no output during the application process, and as a result, they can not work properly. For such situations, generally only need to be properly debugged. Usually we can follow these steps:
1. The power supply should be connected to the input end of the transmitter power supply, and the power supply line should be connected to the power supply wiring port.
2. Detect the power supply of the transmitter, its voltage must be ≥12V, and check if there is 24V DC voltage.
3. Check if the power supply of the pressure transmitter is reversed and the positive and negative connections are correct.
4. If the pressure transmitter has a meter head, then it is necessary to carefully check whether the meter head is damaged. If the meter head is damaged, it needs to be replaced.
5. If the pressure transmitter is faulty, connect the ammeter to the 24V power supply circuit to check if the current is normal.
Pressure transmitter is a commonly used sensor in industrial applications. It is widely used in various industrial self-control environments, involving water conservancy and hydropower, railway transportation, intelligent building, production automation, aerospace, military, petrochemical, oil well, electric power, ship. , machine tools, pipelines and many other industries.
The function of the pressure transmitter is to convert the measured quantity measured by the measuring element into the type of signal required by the controller. The maintenance requirements of the pressure transmitter are checked once a month, and once a week, mainly to remove the dust inside the instrument, carefully check the electrical components, and the current value of the output should be checked frequently. The pressure transmitter is weak inside. Be sure to be separated from the outside world by strong electricity.