Process data

This section describes the individual PDOs and their content. A PDO (Process Data Object) is a unit on cyclically transmitted process values. Such a unit can be an individual variable (e.g. the weight as a 32-bit value) or a group/structure of variables. The individual PDOs can be activated or deactivated separately in the TwinCAT System Manager. The ‘Process data’ tab is used for this (visible only if the terminal is selected on the left). A change in the composition of the process data in the TwinCAT System Manager becomes effective only after restarting the EtherCAT system.

The EL3356 can be used in two basic operating modes

• 1-channel strain gauge evaluation (strain gauge, balance beam, load cell)
  Here, both analog input voltages are measured internally, they are calculated locally according to the internal settings in the terminal and the resulting load value is output to the controller as a cyclic process value. The terminal is to be considered as a 1-channel terminal.
  The load value can be output as an integer or as a float/real representation.
• 2-channel voltage measurement
  Both analog input voltages are output directly as process values; no load calculation takes place.
  The value and status information can be output for each channel.

The basic operating mode of the EL3356 terminal is determined by the selection of the process data (PDO).