壓力變送器作為工業(yè)生產(chǎn)中最重要的一種傳感器，壓力變送器在石油行業(yè)得到了廣泛的應(yīng)用，而且隨著技術(shù)的發(fā)展，壓力變送器的應(yīng)用領(lǐng)域也越來越廣闊。壓力變送器可以實現(xiàn)對氣體、液體等壓力信號的轉(zhuǎn)換，將其轉(zhuǎn)換為4一20 mA的電流信號，二次儀表就可以進行測量、指示和調(diào)節(jié)。目前我國壓力變送器的發(fā)展比較成熟，在長期的進口壓力變送器的市場競爭下，國產(chǎn)壓力變送器已經(jīng)在各項功能及質(zhì)量上媲美進口產(chǎn)品，并且在工業(yè)中取得了良好的應(yīng)用效果，當(dāng)然，產(chǎn)品的使用過程中難免會遇到小問題，所以昆山丹瑞認(rèn)為對壓力變送器的診斷和維護是一項重要的工作，只有正確使用和維護壓力變送器才能確保設(shè)備的長期穩(wěn)定運行。

1、壓力變送器的工作原理        

壓力變送器測量系統(tǒng)的安裝包括三個部分，即導(dǎo)壓管的敷設(shè)、電氣信號電纜的敷設(shè)以及壓力變送器的安裝。在壓力變送器工作過程中，通過隔離膜片和硅油將介質(zhì)的壓力傳送給中心的測量膜片，雙側(cè)隔離膜片上會受到來自于雙側(cè)導(dǎo)壓管的壓差，在這里測量膜片發(fā)揮彈性元件的功能，在壓差的作用下發(fā)生變形。測量膜片的位移和壓差之間存在正比例關(guān)系，而且在膜片位移的影響下，差動電容器的電容量也會隨之變化，測量電路將其轉(zhuǎn)換為4一20 mA的直流電流信號。

2、壓力變送器常見的故障類型         

壓力變送器故障通常是由現(xiàn)場使用和安裝方法不當(dāng)造成的，例如變送器接線錯誤，電源電壓不符合要求、充液管內(nèi)清潔度不夠、一次元件堵塞、指示表頭與儀表接線端子接觸不良等。   

變送器無輸出         

當(dāng)壓力變送器無輸出時，首先檢查變送器電源接線是否正確，如果電源接線沒有問題，接下來測量變送器的供電電源，是否有24 V直流電壓，要求變壓器電源電壓最小12 V。如果變送器是帶表頭的，則先將表頭的兩根線短路，如果故障消失，則說明表頭存在故障。   信號輸出不穩(wěn)定       

如果在壓力不變的情況下，變送器輸出信號值出現(xiàn)跳動現(xiàn)象，首選排除壓力源的不穩(wěn)定，之后檢查傳感器自身震動是否正常，傳感器抗干擾能力是否滿足要求，變壓器是否存在間歇性短路或開路現(xiàn)象;檢查各個穩(wěn)壓二極管、電路板焊接是否牢固、測試振蕩頻率是否穩(wěn)定。       

最后，壓力變送器在石油化工、工業(yè)自控環(huán)境等領(lǐng)域得到了普遍的應(yīng)用，壓力變送器的正確使用維護和故障診斷是確保壓力變送器正常穩(wěn)定工作的關(guān)鍵，這也是使用和維修人員必備的技能。壓力變送器安裝或使用不當(dāng)極易出現(xiàn)故障，而且變送器經(jīng)過長時間的使用后，電子元件和其他器件的性能都會發(fā)生變化，引發(fā)各種問題，變送器測量精度下降，會導(dǎo)致很大的安全隱患，因此研究變送器的故障診斷和維護是十分有必要的。在實際的診斷維修中，應(yīng)結(jié)合變送器的實際情況以及環(huán)境情況，綜合分析，全面排查。

As the most important sensor in industrial production, pressure transmitter has been widely used in petroleum industry, and with the development of technology, the application of pressure transmitter is becoming more and more extensive. The pressure transmitter can convert the pressure signals such as gas and liquid into a current signal of 4120 mA, and the secondary instrument can be measured, indicated and adjusted. Pressure transmitters in our country are relatively mature at present. In the long-term market competition of imported pressure transmitters, domestic pressure transmitters have been comparable to imported products in various functions and qualities, and have achieved good results in industry. Of course, the use of products will inevitably encounter small problems, so Kunshan Than Shwe believes that the diagnosis and maintenance of pressure transmitters is an important work, only the correct use and maintenance of pressure transmitters to ensure the long-term stable operation of equipment.

1. The working principle of pressure transmitter.

The installation of the pressure transmitter measuring system consists of three parts: the laying of the pressure guide pipe, the laying of the electric signal cable and the installation of the pressure transmitter. During the working process of pressure transmitter, the pressure of medium is transmitted to the measuring diaphragm in the center by isolating diaphragm and silicone oil, and the pressure difference from the two side pressure guide pipe will occur on the two side isolating diaphragm, where the measuring diaphragm exerts the function of elastic element and deforms under the action of pressure difference. There is a positive proportional relationship between the diaphragm displacement and the voltage difference, and under the influence of the diaphragm displacement, the capacitance of the differential capacitor will change accordingly. The measuring circuit converts it into a DC current signal of 4120 mA.

2. Common fault types of pressure transmitter

Pressure transmitter faults are usually caused by improper field use and installation methods, such as incorrect transmitter wiring, power supply voltage does not meet the requirements, the cleanliness of the filling tube is not enough, primary component blockage, indicating meter head and instrument terminal contact is not good.

Transmitter no output

When the pressure transmitter has no output, first check the power connection of the transmitter is correct, if the power connection is not a problem, then measure the power supply of the transmitter, whether there is 24 V DC voltage, the minimum voltage of the transformer power supply 12 V. If the transmitter is with the head, the two lines of the head of the meter will be short-circuited first, if the fault disappears, indicating that there is a fault in the head of the meter. Signal output instability

If the output signal value of the transmitter runs out when the pressure is constant, the unstable pressure source should be eliminated first, then the vibration of the sensor itself should be checked, the anti-jamming ability of the sensor should be satisfied, and whether the transformer has intermittent short circuit or open circuit phenomenon. Whether the welding is firm and whether the oscillating frequency is stable.

Finally, pressure transmitter has been widely used in petrochemical industry, industrial automatic control environment and other fields. Correct use, maintenance and fault diagnosis of pressure transmitter is the key to ensure the normal and stable operation of pressure transmitter, which is also a necessary skill for use and maintenance personnel. Pressure transmitter installation or improper use is very easy to fail, and after a long time of use, the performance of electronic components and other devices will change, causing a variety of problems, transmitter measurement accuracy will decline, will lead to great security risks, so the study of transmitter fault diagnosis and maintenance is very important. It is necessary. In the actual diagnosis and maintenance, should be combined with the actual situation of the transmitter and environmental conditions, comprehensive analysis, comprehensive investigation.