The different BaseUnits (BU) facilitate the exact adaptation to the required type of wiring. This enables users to select economical connection systems for the I/O modules used for their task. The TIA Selection Tool assists in the selection of the BaseUnits most suitable for the application.

BaseUnits with the following functions are available:

• Single-conductor connection, with direct connection of the shared return conductor
• Direct multi-conductor connection (2, 3 or 4-wire connection)
• Recording of the terminal temperature for the internal temperature compensation for thermocouple measurements
• AUX or additional terminals for individual use as voltage distribution terminal

The BaseUnits (BU) can be plugged onto DIN mounting rails compliant with EN 60715 (35 x 7.5 mm or 35 mm x 15 mm). The BUs are arranged next to one another beside the interface module, thereby safeguarding the electromechanical link between the individual system components. An I/O module is plugged onto the BUs, which ultimately determines the function of the respective slot and the potentials of the terminals.

Load group formation

Scalable I/O systems usually offer the possibility of individual load group formation. In the case of distributed I/O devices, this previously required an additional power module (feed module) that provided the separation from the left-hand load group as well as the infeed, display, monitoring, and diagnostics of the load voltage. It also featured a filter function against external interference and offered protection against polarity reversal.

All of these functions are now integrated into the basic components of the system in the ET 200SP. For users, this means the elimination of the power module. This saves an additional slot for each load group, resulting in greater flexibility in terms of configuration and ultimately, a saving of storage space.

A light-colored BU separates the self-assembling, internal voltage buses (P1, P2, AUX) and thus opens a new load group. The power supply of a load group must be fed in at the light BU of this load group.

A dark BU forwards the power supply of the adjacent light BU on the left via the self-assembling voltage buses P1, P2 and AUX. A new infeed is therefore only required on the next light BU to the right. The setting of a further light BU is required whenever

• a new load group is to be formed (for example, for isolating the supply voltage from module groups) or
• the maximum current simultaneously required by the load group exceeds the permissible limit of 10 A.

Labeling

Equipment labeling plates

Equipment labeling plates enable the equipment to be easily identified (e.g. compliant with EN 81346). They are easily plugged onto the required component (interface modules, I/O modules and BaseUnits) and when required, they can be easily replaced with the component.

The following labeling components are available:

• Equipment labeling plates, white, ten sheets each with 16 labels, for thermal transfer card printers or labels

Color identification of the terminals

The potentials at the terminals of the BaseUnit are defined by the I/O module. Optionally, the potentials of the terminals can be identified by module-specific color-coded labels to prevent wiring errors. The color-coded label that matches the respective I/O module is defined by the color code CCxx of the I/O module. This color code is also printed on the front of the module.

In BaseUnits with 10 internally jumpered AUX terminals, these can also be identified with color-coded labels. For the 10 AUX terminals, color-coded labels are available in red, blue, and yellow/green.

System-integrated shielded connection

For the space-saving and EMC-optimized connection of cable shields, a shield connection is available that is quick and easy to mount. This consists of one shield connection element that can be plugged onto the BaseUnit and one shield terminal for each module. The low-impedance connection to the functional ground (DIN rail) is achieved without any additional wiring by the user.

The BaseUnits can be equipped with an equipment labeling plate.