The FM 355-2 has 4 mutually disconnected closed-loop control channels. The controllers display the following features:

• Standard control structures (depending on the control structure selected, a number of different types of control may be interconnected in a single structure:
  • Fixed setpoint control,
  • Cascade control,
  • Ratio control,
  • 3-component control.
• Choice of modes:
  Automatic, manual, safety mode, follow-up mode and backup mode.
• Sampling interval:
  100 ms to 500 ms (depending on the number of enabled analog inputs)
• PID algorithm
• Integrated online self-optimization:
  The self-optimization function is stored on the module and can be executed without the configuration tool, e.g., via an operator panel. The new optimization algorithm can also be started from an almost stationary state (the temperature approaches a stationary state asymptotically). It is not necessary to wait until a warmed up process has cooled down to the ambient temperature. The PID parameters are available as soon as the turning point of the step response is reached. This causes the operating point to be achieved more rapidly.
• Stepless distribution of the P component onto the reference branch and feedback branch:
  Stepless distribution supports precisely proportioned reduction of the effect of the P component in the case of setpoint step changes and therefore an optimum control response.
• Adjustable control zone:
  The controller has an adjustable control zone. If the actual value is located within the control zone, the controller will operate in closed-loop control mode. To ensure that the operating point is achieved quickly, when the actual value lies outside the closed-loop control zone, automatic switchover to open-loop control takes place, whereby the maximum setting for heating or cooling is used.
• Backup mode:
  In the event of CPU failure or CPU Stop, the controller can continue to operate independently. The "backup mode" function is used to set a parameterizable safety setpoint or a parameterizable safety control variable.
• Disturbance variable input:
  The analog inputs can be used for feedforward compensation in addition to actual value acquisition, if desired.
• Temperature compensation:
  When thermocouples are used, temperature compensation is possible using an:
  • Integrated temperature sensor
  • External Pt 100
  • Parameterized comparison temperature

Parameterization

A configuration package is supplied with the FM 355-2 that contains all the parameter screen forms that are required for parameterization and startup.

Detailed online Help is available for all screen forms. The parameterization screen forms are called up from STEP 7 following installation.