8-channel P-reading input for ET 200SP
The Siemens 6ES7131-6BF00-0BA0 is an 8-channel digital input module for the ET 200SP distributed I/O system, accepting 24 V DC signals in P-reading (source/sink input) configuration. Each channel draws a typical 2.5 mA at signal "1" (11 to 30 V), with signal "0" defined from -30 to +5 V — the thresholds are standard for 24 V PLC inputs and compatible with most 3-wire sensors and proximity switches. The module sits on a BU type A0 base unit, which handles the 1-wire, 2-wire, and 3-wire sensor connections; for 4-wire sensors you add external terminals to the A0 base unit with AUX terminals.
Wire-break diagnostics and encoder supply
Wire-break detection is configurable module-by-module, with an optional protective circuit that uses a 25 kOhm to 45 kOhm resistor to prevent false wire-break alarms on simple encoder contacts — a detail that matters when you have mechanical limit switches or reed contacts that sit open for long periods. The module provides a 24 V DC encoder supply (min 19.2 V) with a total output current of 700 mA across all encoders — enough to power a bank of proximity sensors or a small encoder cluster without an external power supply. Short-circuit protection is module-wise, and diagnostic alarms are generated for wire-break and short-circuit events, with I&M data (I&M0 to I&M3) for asset tracking.
Panel fit and cabling limits
Unshielded cable runs up to 600 m are allowed; shielded cable extends to 1 000 m — the longer run is useful when the I/O rack sits in a central cabinet and the field devices are distributed across a large plant. Power dissipation is 1 W typical, so no special derating or forced cooling is needed in a standard IP20 enclosure.
Firmware version V1.1 is field-upgradable, and the module supports automatic encoding on the backplane bus, so a replacement swaps in without manual configuration.