I think it's intelligent positioner.

Here an explaination from a manufacturer of them.

Intelligent positioner - SIEMENS Industry Sector Sensors and ...

"The intelligent positioner SRD991 is designed to operate pneumatic valve actuators and can be operated from

control systems (e.g. the Foxboro I/A Series System), controllers or PC-based configuration- and operation tools

such as the FDT/DTMs VALcare™ or Valve Monitor. The positioner is available with different communication

protocols. The multi-lingual full text graphical-LCD (optional with infrared interface), in conjunction with the 3 push

buttons, allows a comfortable and easy local configuration and operation. For installations in contact with explosive

atmospheres, certificates are available."

http://www.imaha.cz/media/files/shop/srd991.pdf

They have many more functions then a conventional positioner. They have all kinds of error reporting, auto stroke, auto tune and some other very usefull features.

You must of course be using a signal protocol that can communicate with the positioner. If you use it on a conventional 4-20 ma loop the advantages are mostly lost.

The main drawback I have seen is they are so minaturized ( an I/P the size of a box of matches ) that they are delicate and not tolerent to vibration or dirt.

On a very large air compressor ( 30,000 HP ) with guide vane actuators on the 1st and 2nd stage.

I sometimes had one or the other fail once a year or certainly a failure every two years. In other applications with much less heat and vibration I have had some units last 10 years.

If you must use one then be carefull to avoid vibration and make sure your inst. air supply is very very clean.

The temp and vibration issues can be solved with remote mount positioners. The feed back is mounted to the actuator and the positioner is mounted in a cooler place with no vibration.

>If you use it on a conventional 4-20 ma loop the advantages are mostly lost.

I disagree. A smart positioner saves, on average 1.5 hours on start-up, even with just the 4-20mA control signal.

1) What do you do if the valve needs direct action, not reverse action the dumb one came with? Take the non-smart positioner apart and flip the cam. On a smart unit, pick the action needed.

2) If a characterized cam is needed, then take the dumb one apart and install another cam. On a smart positioner, select a different response curve.

But what really saves time is the auto start-up provided most (probably all) smart positioners. I figure it elimates at least an hour's fumbling around making minor adjustments with a dumb positioner.

My point was that with a 4-20 ma loop you lose the realtime error reporting that is always used as a main selling point.

If your only concern is start-up time then the 1 to 1 1/2 hours of Inst. tech time is probably much cheaper then the added cost of the high end inteligent positioner. Also most dumb positioners should not take a competent Inst. tech. 1 to 1 1/2 hrs to set up. There are others that are a pain in the ### and can take a long time to set up.

Don't get me wrong in the right application I love how easy they are to use and modify but in my experience they are not as robust and maybe somewhat too delicate in some applications.