Electro-pneumatic positioner DE/3M-3-EP (fig. 2) are modular, consisting of a pneumatic positioner DE/3M-3 (fig. 1) and an electro-pneumatic transducer. The two units are assembled together. Positioner DE/3M-3-EP is based on the balanced-forces principle. it is basically composed as follows:
? an electro-pneumatic transducer operated by the electrical control signal;
? a diaphragm operated by pneumatic control signal originated by the transducer;
? a reverse feed-back spring;
? a double-acting spool valve connected to a diaphragm and spring through the stem.
Double-acting positioner DE/3M-3-EP can be converted to simple-acting positioner by plugging the connection between the positioner and the cylinder chamber on the shaft's side. Moreover it is necessary to install a system for cylinder's return.

Digital Trak is a smart positioner and it is a loop powered instrument. As a control part of the pneumatic valve set, this item is widely used in petroleum, chemical, electric power, metallurgy, light industry and other fields of automation systems. 
DT Intelligent Electro-pneumatic valve Positioner accepts the 4/20 mA valve setting signal from the control system. At the same time, it gets the actual valve signal through the location sensors; the two signals are compared by control software in order to control the feeding and exhaust of the gas to actuator and to drive the valve to reach set point.
This product is based on microprocessor technology. It can overcome friction and the imbalance power on the control valve well, and improve the response speed of control valve, which makes the position set rapidly and accurately.

FasTrak is a smart positioner and its has a high-capacity, high-precision digital-pneumatic valve controller that replaces a conventional positioner. It has an excellent dynamic performance and high flow (Cv = 2).
His configuration and calibration is made through Hart device or by self calibration. FasTrak is compatible with double and single acting actuators, with or without spring, piston or diaphragm.
Tight shut off and travel limit position are independently adjustable up to 50% of stroke to open and to stroke. 
The pressure shut off to open and to close is independently adjustable.
Positioner’s parameters can be easily selected from a Remote Control device.
This product has two digital inputs and outputs. The first ones are used to fully open or fully close the actuator. The second ones are used as virtual limit switch or to indicate position error or low pressure. The power/signal fail position can be mechanically configured.