samson 3725 定位器

Series 3725

Electropneumatic Positioner Type 3725

Application

Single-acting positioner for attachment to pneumatic globe and rotary valves.Self-calibrating,automatic adaptation to valve and actuator.

Reference variable 4 to 20 mA Travels 3.75 to 50 mm Opening angles 24 to 100°

The positioner ensures a predetermined assignment of the valve stem position (controlled variable x)to the electric input signal (reference variable w).It compares the control signal received from a controller to the travel or opening angle of the control valve and issues a corresponding output signal pressure (output variable y).

Special features

•Simple direct attachment to SAMSON Type 3277Actuator (120 to 700 cm², Fig. 1)

•Attachment according to NAMUR (IEC 60534-6-1)

•Attachment to rotary actuators according to VDI/VDE 3845(Fig. 3)

•Attachment to SAMSON Type 3372Actuator from the V2001 valve series (Fig. 2)

•Easy operation with intuitive navigation menu using three ca-pacitive keys

•LCD easy to read in any mounting position due to selectable reading direction

•Variable, automatic start-up

•Preset parameters –only values deviating from the standard need to be adjusted

•All parameters saved in EEPROM (protection against power failure)

•Two-wire system with a small electrical load of 300W •Tight-closing function can be activated •Continuous monitoring of zero point •Non-contact position sensing

•Unaffected by environmental effects and steam hammering

Version

–Type 3725·Electropneumatic postioner with local opera-

tion and LCD

Associated Information Sheet T 8350EN Edition December 2011

Data Sheet

T 8394 EN

Fig.1

Type 3725,direct attach-ment to Type 3277Pneumatic Actuator

Fig.3

Type 3725,attachment to rotary actuator according to VDI/VDE

3845

Fig.2

Type 3725,attachment to Type 3372Actuator

Principle of operation

The electropneumatic positioner is mounted on pneumatic con-trol valves.It is used to assign the valve stem position(controlled variable x)to the input signal(reference variable w).The input signal received from a control system is compared to the travel or opening angle of the control valve and an output signal pres-sure (output variable y) is produced.

The positioner consists of an anisotropic magnetoresistive (AMR)sensor(2),an analog i/p converter(6)with a down-stream booster(7)and the electronics unit with microcontroller (4).

The travel or opening angle is measured by the pick-up lever connected to a magnet and an AMR sensor installed in the hous-ing.The motion of the pick-up lever causes the direction of the magnetic field to change.This change is sensed by the AMR sensor.The microprocessor determines the momentary valve position from this information.

When a deviation occurs,the actuator is pressurized or vented. If required,the changes in the signal pressure can be slowed down by a volume restriction.

The i/p module(6)is supplied with a constant upstream pressu-re by the pressure regulator(8)to make it independent of the supply air pressure.Operation

A user-friendly,intuitive concept using three capacitive keys and a LCD has been developed:Users select parameters by touching the arrow keys and confirm the settings with the confir-mation key.In the menu,all parameters are listed in one level, meaning there is no need to search through submenus.All pa-rameter settings can be read and changed on site.

All values are displayed on the LCD.The reading direction of the LCD can be rotated by 180°.

2T8394EN