CiA® 404: CANopen device profile for measuring devices and closed-loop controllers

This device profile is dedicated to analog transducers that may also provide digital I/O capability. Additionally, the profile describes closed-loop controllers that collect sensor signals and provide set values for actuators. Devices compliant to CiA 404 may support up to 199 transducer channels. The analog input function distinguishes between field value and process value. Field values are non-scaled readings from the analog/digital converter, counting from the incremental encoder, or calibrated electrical values provided by a transformer. This value is converted to the physical dimension or the measured quality, and the result is called process value. Examples for process values are a value in kg for weight measurement, a value in °C for temperature measurement, or a value in mm for displacement measurement. The transducer parameters are given in selectable resolutions (8-bit, 16-bit, and 32-bit integer, or Real32).

The closed-loop controller function provides the PID algorithm with two set points, a manual override, and self-optimization. The device is configurable as a 2-point or a 3-point controller. The output of the PID controller can be limited, e.g. in order to ensure minimum and maximum pressure. Via the self-optimization algorithm, it is possible to calculate the necessary PID parameters automatically.

Multi-channel sensor devices can be connected to one or more actuator devices or closed-loop controllers. These sensor signal-collecting devices provide a second CANopen network interface in which they provide sensor signals. This allows the design of cascaded CANopen transducers.

The CiA 404 profile doesn’t comply with the logical device approach as defined in the CiA 301 application layer. It uses all object dictionary addresses from 6000h to 9FFFh. This means that the device maker can’t implement different instances or multiple profiles in the CANopen device with a single node-ID. Of course, you can implement multiple protocol stacks to extend the functionality.

The CiA 404 profile was originally a single document. Since version 2.0.0 it has been split into two parts. Part 1 includes the definitions as given in the previous version. The PDO (process data object) mapping is now implementation-specific by default. Part 2 specifies some measuring amplifier parameters needed in the Euromap 75 specification. The Euromap 66 specification for an injection molding machine refers to a subset of part 1 parameters.

The CiA 404-1 version 2.1.0 reincludes the possibility to define a physical unit for the field values of analog inputs. Some object definitions (e.g. 6150h, 6160h) were specified more exactly. Additionally, the document was completely editorially reviewed and corrected.