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#53556 06/29/05 10:42 AM
Joined: Apr 2004
Posts: 156
R
rad74ss Offline OP
Member
I have a customer who is looking for a pressure transducer for an R404A refrigerant system. He wants the range to be 30"Hg to 150PSIG and 30"Hg to 300PSIG for the two transducers. [Linked Image]

30"Hg is way, way, way off my chart, and my chart stops at 6.8"Hg = -60 degrees F.

This system is designed with a suction temperature of 35 degrees. It will trip out before it gets much lower than that.

Our standard transducers are -14.5 to 116 PSIG and 0 to 435PSIG. But the customer still wants the transducer in his range. [Linked Image]

I have googled for two hours and found nothing in his range. The only one that came close costs more than all the other electrical components on the unit combined.

Does anyone know of a transducer that will fit in his range?

I would appreciate any leads.

Thanks,

Robert

#53557 06/29/05 11:03 AM
Joined: Feb 2005
Posts: 361
C
Member
Have you checked at www.rosemount.com ?


~~ CELTIC ~~
...-= NJ =-...
#53558 06/29/05 12:01 PM
Joined: Sep 2003
Posts: 650
W
Member
I think that your problem is a units conversion issue. 30"Hg is simply -14.7PSIG... What you really want is some sort of transducer that works from 0 to 315 PSIA. (PSI _absolute_, meaning relative to perfect vacuum, rather than PSIG, relative to atmospheric pressure)

People think in terms of inches of mercury for vacuum and PSI for pressure. Because people think this way you can buy mechanical gauges that read 30"Hg to 0 to 300 PSIG. But a transducer is something that converts the mechanical data (pressure) into an electrical signal. You want something that will work over the pressure range of vacuum (0 PSIA ) to pressure (315 PSIA), and then you will do your limits or display based upon the electrical output of this transducer.

-Jon

#53559 06/29/05 12:22 PM
Joined: Apr 2004
Posts: 156
R
rad74ss Offline OP
Member
I forgot about the Hg to PSI conversion. I am still having problems finding anything that will cover that range. Especially the 30" to 300PSI. The majority that go into vacuum only read up to 10 to 15 PSI. Our standard transducer is the only one I can find that will go up to 116 from vacuum.

I think the customer is going to have to go with the ones we have right now. They will cover the minimum and maximum that the unit will operate in with room left over at both ends.

#53560 06/29/05 01:42 PM
Joined: Sep 2003
Posts: 650
W
Member
Would something like this be suitable: http://www.omega.com/ppt/pptsc.asp?ref=PX209_PX219

I'm more used to thinking about instrumentation rather than industrial controls.

-Jon

#53561 06/29/05 02:02 PM
Joined: Nov 2000
Posts: 2,148
R
Member
Try a search here .


Don(resqcapt19)

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