Siemens Welding System ST PCS 7 User Manual

ET 200M distributed I/O

Siemens ST PCS 7 · November 2007

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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

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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.

© Siemens AG 2007