pressure ratings, psi, psia, psid, psig, what do they mean?

Discussion in 'After Hours Lounge (Off Topic)' started by ShaneH, Nov 30, 2003.

  1. ShaneH

    ShaneH Stunt Coordinator

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    I'm looking for a pressure transducer and I'm running into these different ratings. I know what psi is, but what do the other ratings mean? They also come as absolute or gauge, whats the difference between the two?

    Also does anyone know a good online place for pressure transducers? So far digikey has been the best source I have found. Thanks
     
  2. Eric Kahn

    Eric Kahn Guest

    PSIA is pounds per square inch absolute, meaning that 0 is 0 psi or a complete vacuum, normal air pressure would be about 14.5 on a PSIA guage

    guage pressure is PSI over atmosperic, reads zero in normal air pressure

    I believe Psid is differential pressure between 2 sides of a system
     
  3. Mike Voigt

    Mike Voigt Supporting Actor

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    AS Eric pointed out, PSIA is psi Absolute, i.e. includes pressure of air (approx. 14.7 at sealevel).

    PSIG is psi Gauge, i.e. does not include air pressure. Add 14.7 to get PSIA.

    PSID is psi differential, checks for delta-P across things like filters, pumps, etc. Is technically also psi-g, but since they (usually) cancel out on both sides, that is usually ignored...
     
  4. David_Moechnig

    David_Moechnig Stunt Coordinator

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    What kind of transducers are you looking for? There are differential pressure transducers that use a pizeo crystal and a charge amp to measure pressure differences and absolute pressure transducers that use a diaphram and strain gauges to determine pressure.
     

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