Interested to Buy Any Domain ? << Click Here >> for more details...
Answer Posted / carl_ellis
Because it's a standard, widely used conventional pneumatic
control transmission range.
The 3-15 psi signal is a standard (ISA SP7) that came from
widespread use even before that standard came into being.
As early as the 1920's pneumatic regulators, pressure and
temperature controllers were using 15 psi at the high end.
Various low end 'live' or elevated zero values were used
before standardization.
Any pneumatic control or transmission signal starts with an
'elevated' or 'live' zero' at 3 psi because there is
internal friction and a fair amount of hysteresis in the
movement of pneumatic components, the flapper, nozzle,
diaphragms, spring preloads, pivots and bellows that make up
the transmitters and receivers. This friction and
hysteresis manifests as non-linearity below 3 psi. A 3 psi
minimum pressure puts the transmission signal into a linear
response range. Obviously, control system measurements,
signal transmission and the receivers need a linear response
to effect accurate and precise control.
Not all pneumatic control signals are in the 3-15 psi range.
The ISA SP7 standard (1996) that addresses instrument air
quality standards also lists 5-25 psi, 6-30 psi, 3-27 psi as
standard pneumatic transmission ranges, along with the
minimum supply pressure associated with each range. These
ranges all include an elevated zero.
Carl Ellis
Measure First
| Is This Answer Correct ? | 22 Yes | 0 No |
Post New Answer View All Answers
few questions on RS 232,1 question on relationship of impedance and turns ratio, many questions on flowmeters
can anyone can let me know in Eurotron Micro cal 2+ calibrator in milli amps source mode we are not able to get 20 milli amps output it only produces 1.52 milli amps out, but display shows increase in milli amps , and err6 displays, let me know how to remove the err 6.
what is the procedure of belt scale calibration?
HOW TO SOLVE PROBLEM WITH ENRAF LEVEL TRANSMITTER 854 ATG THAT PASSWARD DO NOT Exist INTO TRANSMITTER TO ADJUST LEVEL WITH PORTABLE PET 847, WRITTEN WRONG PASSWORD , I AM SURE THAT DEFAULT PASSWARD (W2=ENRAF2) IS THIS TRANSMITTER NEED TO REPLACE SOFTWARE AND HOW?
What are de-saturators?
sir, i preparing hpcl,ongc,barc,hal exams(instrumentation engg)pls send a placement papers
Type of level transmitter commnly used in Procees area are the following. a.________________This type of level transmitter works as follows
I am manjunath having exp in maintenance of chemical plants,know i want to do a design course INTOOLS,after doing design course can we get jobs in design field.sinve i dont have design exp..
what different types of problems do occur while doing instrumentation commisioning and how to solve them? please explain in detail
please send the sample qustion paper for iocl written test ..
how to calculate control valve bonnet size?? or how to select its material?
How to do gas analysers calibration in AUTO and Manually by using zero and span gas?
What is the use of each wire in three wire RTD
Why thermo wells are used? What materials are used in thermo wells?
what do u mean by compensation n pid tunning?in pid tunning what you tunned?is it possible 2 tune p i d
