What are the forms of pressure gauge selection?Introduction of Xi'an Huaheng Instrument:Correct selection of instrument types according to product process requirements is an important prerequisite for ensuring normal operation and safe production of instruments.Usually when choosing the type of pressure gauge,the following three requirements should be considered:

 

　　(1)根據(jù)工業(yè)生產(chǎn)中產(chǎn)品工藝的要求選擇。例如是否需要遠(yuǎn)傳、自動記錄或報警；

　　(2)根據(jù)被測介質(zhì)的物理化學(xué)性能(諸如腐蝕性、溫度高低、粘度大小、臟污程度、易燃易爆性能等)是否對測量儀表提出特殊要求選擇；

　　(3)根據(jù)現(xiàn)場環(huán)境條件(諸如高溫、電磁場、振動及現(xiàn)場安裝條件等)對壓力表類型有否特殊要求等選擇。

 

　　(1)Selection according to the requirements of product process in industrial production.For example,whether remote transmission,automatic recording or alarm are needed;

　　(2)According to the physical and chemical properties(such as corrosiveness,temperature,viscosity,dirty degree,inflammable and explosive properties)of the medium under test,the special requirements for the measuring instruments are selected.

　　(3)According to the site environmental conditions(such as high temperature,electromagnetic field,vibration and site installation conditions),whether there are special requirements for pressure gauge types and so on.

 

　　1、壓力表的測量范圍的確定:為了合理、經(jīng)濟(jì)使用儀表，儀表的量程不能選得太大，但為了保證測量精度，一般被測壓力的最小值不低于儀表滿量程的1／3為宜。同時為了延長彈性元件的使用壽命，避免彈性元件因長期受力過大而永久變形，壓力計的上限值應(yīng)該高于被測量的最大值(量程的1／2~1／3)，留有余量。

 

　　1.Determining the measuring range of pressure gauge:In order to use the instrument reasonably and economically,the measuring range of the instrument can not be too large,but in order to ensure the measuring accuracy,it is generally advisable that the minimum value of the measured pressure is not less than one third of the full measuring range of the instrument.At the same time,in order to prolong the service life of the elastic element and avoid the permanent deformation of the elastic element due to long-term excessive force,the upper limit value of the pressure gauge should be higher than the maximum value of the measured value(1/2-1/3 of the range),leaving a margin.

 

　　2、壓力表精度的選取:壓力表精度是根據(jù)工藝生產(chǎn)上所允許的最大測量誤差來確定的。不能認(rèn)為選用的儀表精度越高越好，應(yīng)在滿足工藝要求的前提下，盡可能選用精度較低、價廉耐用的儀表。

 

　　2.Selection of pressure gauge accuracy:pressure gauge accuracy is determined according to the maximum measurement error allowed in process production.It can't be considered that the higher the accuracy of the selected instrument,the better.On the premise of meeting the technological requirements,the instrument with lower accuracy and low cost and durability should be selected as far as possible.

 

　　儀表類型選擇實例：某臺壓縮機(jī)的出口壓力范圍為25～28MPa，測量絕對誤差不得大于1MPa。工藝上要求就地觀察，并能高低限報警，試正確選用一臺壓力表，指出型號、精度與測量范圍。要求條件為：被測脈動壓力25～28MPa，測量絕對誤差≤1MPa，就地觀察、高低限報警。

 

　　Examples of instrument type selection:The outlet pressure of a compressor ranges from 25 to 28 MPa,and the absolute error of measurement should not be greater than 1 MPa.The technology requires on-site observation and alarm at high and low limits.A pressure gauge should be selected correctly and the type,accuracy and measurement range should be pointed out.Requirements are:the measured fluctuating pressure is 25-28 MPa,the absolute error of measurement is less than 1 MPa,in-situ observation,high and low limit alarm.

 

　　儀表選擇時考慮脈動壓力對儀表壽命影響很大，故選擇儀表的上限值為：P1=Pmax*2=28*2=56MPa若選壓力表的測量范圍為0～60MPa，則：25MPa／60MPa>l／3，被測壓力的最小值不低于滿量程的1／3，下限值也符合要求。另外，根據(jù)測量誤差的要求，可算得對儀表允許誤差的要求為：1／60*100％=1．67％，故選精度等級為1．5級的儀表，可以滿足誤差要求。

 

　　When choosing the instrument,the fluctuating pressure has a great influence on the life of the instrument.Therefore,the upper limit value of the instrument is:P1=Pmax*2=28*2=56MPa.If the measuring range of the selected pressure gauge is 0-60MPa,the minimum value of the measured pressure is not less than 1/3 of the full range,and the lower limit value also meets the requirements.In addition,according to the requirement of measurement error,it can be calculated that the allowable error of the instrument is 1/60*100%=1.67%.Therefore,the instrument of 1.5 precision level can meet the error requirement.