要应从7个方面着手：一、测量材质二、精度等级三、量程四接液介质五、介质温度六输出信号七、其他因素 Selecting a pressure transmitter should start from 7 aspects: 1. measuring material 2. accuracy level 3. measuring range 4. wetted medium 5. output signal 6. medium temperature 6. other factors
1.Measurement medium 2.Accuracy level.Every electronic measuring meter will have accuracy error, but because the accuracy level of each country is different, for example, the accuracy of national standards such as China and the United States is the most accurate. Good points, which is what we usually call the accuracy between 10% and 90% of the measurement range; and European standard accuracy is the worst linearity point, which is what we usually call the measurement inverse 0 to Accuracy between 10% and 90% to 100%. If the accuracy of the European standard is 1%, the accuracy of the Chinese standard is 0.5%. 3. The maximum range of the range and general sensor measurement is 70% of the full scale of the sensor. OK, that is to measure the pressure of 70bar now, we should choose the range of the pressure transmitter should be 100bar. 4, the output signal, due to various acquisition needs, there are many output signals of pressure transmitters on the market today , Mainly 4 ... 20mA, 0 ... 20mA, 0 ... 10V, 0 ... 5V, etc., but the more commonly used are 4 ... 20mA and 0 ... 10V, which are above me Of these output signals, only 4 ... 20mA is a two-wire system (the output we are talking about is a few-wire system and does not include grounding or shielding Wire), the others are three-wire system. 5. Since the signal of the pressure transmitter is converted by the electronic circuit, the temperature of the measuring medium of the pressure transmitter is generally -30 to +100 degrees. Too high, we generally use condensation bends to cool the medium, so that the cost of letting the manufacturer to produce a high temperature pressure transmitter for you will be much reduced.
6.Wetted material, we have to consider the medium measured by the pressure transmitter. The material of the contact medium of the general pressure transmitter is 316 stainless steel. If your medium is not corrosive to 316 stainless steel, then Basically all pressure transmitters are suitable for you to measure the pressure of the medium. If your medium is corrosive to 316 stainless steel, then we must use a chemical seal, so that it can not only measure the pressure of the medium, but also effectively Prevent the medium from coming into contact with the wetted parts of the pressure transmitter, thereby protecting it and prolonging the life of the pressure transmitter. 7. Other factors, we must confirm your pressure transmission after determining the above five parameters. The process connection interface of the transmitter and the power supply voltage of the pressure transmitter; if it is used in special occasions, it must also consider the explosion-proof and protection level. Generally, we measure relatively clean fluids, so we use standard pressure transmitters directly. It is OK, if the medium you are measuring is easy to crystallize or sticky, we generally use an external diaphragm or use it with a chemical seal, which will be effective Blocking medium to prevent the pressure measurement holes.
超时工作后需要保持稳定度，大部分变送器在经过超时工作后会产生“漂移”，因此很有必要在购买前了解变送器的稳定度，这种预先的工作能减少将来使用中会出现的种种麻烦。 Pressure transmitters need to maintain stability after overtime work. Most transmitters will "drift" after overtime work, so it is necessary to know the stability of the transmitter before purchasing. This kind of pre-work can reduce Various troubles will occur in future use. The package of the transmitter, especially its frame, is often easy to overlook, but this will gradually expose its disadvantages in future use. When purchasing the transmitter, you must consider the working environment of the transmitter, the humidity, how to install the transmitter, and whether there will be strong impact or vibration. What kind of output signal the pressure transmitter needs to get: mV, V, mA and frequency output digital output, depends on many factors, including the distance between the transmitter and the system controller or display, whether there is "noise" or other electronics Interfering signals. Whether an amplifier is needed, the location of the amplifier, etc. For many OEM devices with a short distance between the transmitter and the controller, a transmitter using the mA output is the most economical and effective solution. If the output signal needs to be amplified, it is best to use a transmitter with a built-in amplifier. For long-distance transmission or strong electronic interference signals, it is best to use mA output or frequency output. If the RFI or EMI index is high, in addition to paying attention to the choice of mA or frequency output, special protection or filters must be considered. (At present due to various acquisition needs, there are many output signals of pressure transmitters on the market, mainly 4-20mA, 0-20mA, 0-10V, 0-5V, etc., but the more commonly used is 4- 20mA and 0-10V. Of the output signals I mentioned above, only 2-20mA is a two-wire system. The output we are talking about is a few-wire system without ground or shielded wires. The others are three-wire systems.) .
The type of output signal determines what excitation voltage is selected. Many amplifier transmitters have built-in voltage regulators, so their supply voltage range is large. Some transmitters are of a quantitative configuration and require a stable working voltage. Therefore, a working voltage that can be obtained determines whether a sensor with a regulator is used. When selecting a transmitter, the operating voltage and system cost must be considered comprehensively. Do you need interchangeable transmitters and determine if the required transmitter can accommodate multiple use systems. In general, this is important. Especially for OEM products. Once the product is delivered to the customer, the cost of the customer's calibration is considerable. If the products have good interchangeability, even if the transmitter used is changed, it will not affect the effect of the entire system. 的过程连接接口以及压力变送器的供电电压；如果在特殊的场合下使用还要考虑防爆以及防护等级。 Others: After we determine some of the above parameters, we must also confirm the process connection interface of your pressure transmitter and the power supply voltage of the pressure transmitter; if it is used in special occasions, it must also consider the explosion-proof and protection level.