***WAY OT***, Supply Sensitive E/P

This is way off topic but there are enough people around here that I just might find an answer.

I need to use an E/P (voltage to air pressure) transducer on an upcoming job. I asked our customer if he had a preference for an E/P manufacturer and he stated:

Originally written by my customer:

If it’s a true proportional scaled to available air supply we will probably approve. If it’s of a type typical of Proportion-Air, where 1 volt = 10psi and using a supply of 30 psi reduces the resolution to 0-3 volts we will likely object.

Click to expand...

Up until this point I didn't know there was such a thing as an E/P that was intentionally sensitive to supply pressure. Have any of you come across such a device and, if so, who makes it?

Thanks,
Keith

I also thought E/P or I/P transducers were specifically designed to provide an output proportional to its input, as long as the supply maintained some minimum. The blurb for Bellofram says effectively that:

"The Bellofram Type 1000 Transducer is an electro-pneumatic
device that reduces a supply pressure to a regulated output pressure directly proportional to an electrical input signal. The Type 1000 accepts a wide range of supply pressures, ranging from a minimum of 3 psig (0.2 BAR) above the maximum output up to 100 psig (6.9 BAR). An integral pneumatic volume booster is included in the design to provide high flow capacity (up to 12
SCFM/339 slpm)."
I have only used 4-20mA control signals with the I/P models, where input of 4-20mA = 3-15psi output, proportional, as long as supply is 18 psi minimum (3 psi > 15 psi max)

The E/P models listed are 0-5V and 1-9V dc, presumably with some rangeability.

I did notice the input for E/P's was fairly low, about 600 ohms, which could load your voltage source, or require tweaking to adjust for too loading.

I wonder if your customer was using an E/P ranged 0-10V input = 1-100 psi output and then supplied only 30 psi to it and was shocked that it couldn't supply more than 30 psi ? ?

Dan

I think they have been confused at some point. There are quite a few that work with 3-15/30 PSI and 0=5v etc: http://www.controlair.com/index.html

I think they got confused because of some kind of specialty application though.

I believe all they are speccing is to use the 30 PSI max w/ 10 Volt input so they have full resolution, rather then 100 PSI max & using a 3 volt signal to drive it.