Siemens ST PCS 7 manual Closed-loop control modules, 11/27

© Siemens AG 2007

Process I/O

ET 200M distributed I/O

Closed-loop control modules

■Overview

The FM 355 is an intelligent 4-channel controller module for uni- versal control tasks. It can be used to control temperature, pres- sure and flow.

The following versions of the FM 355 are available:

•FM 355 C

Continuous-action controller with 4 analog outputs for control- ling analog actuators

•FM 355 S

Step or pulse controller with 8 digital outputs for controlling motor-driven (integrating) actuators or binary controlled actu- ators (e.g. electrical heating strips and cartridges)

•FM 355-2 C/S

Specially optimized for temperature controls with user-friendly online self-optimization integrated

■Function

The FM 355 / FM 355-2 modules have four separate control channels. These controllers have the following features:

•Predefined controller structures for

-fixed-setpoint control,

-cascade control,

-ratio control,

-3-component control

•Various operating modes:

-automatic mode,

-manual mode,

-safety mode,

-follow-up mode,

-backup mode

•Sampling interval (dependent on the resolution of the analog inputs and the compensation input):

-at 12 bit: 20 ms to 100 ms (only FM 355-2)

-at 14 bit: 100 ms to 500 ms (dependent on the number of en- abled analog inputs)

•2 control algorithms:

-self-optimized temperature control algorithm,

-PID algorithm

•Integrated online self-optimization without configuration (only FM 355-2)

-for faster adoption of the operating point

•User-friendly controller optimization

•Backup mode: The controller can maintain its control function in the event of CPU failure or CPU stop. Programmable safety setpoint values or safety manipulated variables are set for this purpose.

•Feedforward control: The analog inputs can be optionally used for feedforward control as well as for actual value acqui- sition.

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Siemens ST PCS 7 · November 2007

11/27