Siemens 6ES7350-1AH03-0AE0 FM 350-1 Counter Module
The Siemens 6ES7350-1AH03-0AE0, also known as FM 350-1, is a 40 kHz counter module for the S7-300 PLC system. It is designed for high-speed counting, position feedback, and frequency measurement from incremental encoders (24 V TTL or HTL) and proximity switches. The module occupies one slot in the S7-300 rack.
Counter Features
Number of counters: 1. Maximum counting frequency: 40 kHz (differential) or 20 kHz (single ended). Counter depth: 32 bits (range -2,147,483,648 to +2,147,483,647). Operation modes: continuous counting, single (one-shot), and period measurement. The module can count up, down, or up/down (directional). Gate control via hardware input or software command. Three digital inputs (24 V DC) for latch, gate, and sync functions.
Encoder Interface
Supports incremental encoders with A/B (90° phase shift), A/B with reverse signal (A-/B-), or single pulse with direction. Input frequency: up to 40 kHz for RS-422 differential signals, 10 kHz for 24 V single-ended signals. Encoder supply: 5 V DC (300 mA) or 24 V DC (300 mA) selectable. Also compatible with NAMUR proximity sensors (EN 60947-5-6).
Digital I/O and Outputs
Two digital outputs (24 V DC, 500 mA each) can be configured as limit value switches (comparator outputs) or pulse generators. For example, one output can activate a clutch when the counter reaches a preset value. The outputs are short-circuit protected and have status LEDs on the front panel.
Configuration and Programming
The module is configured via STEP 7 (V5.5+ or TIA Portal) using the FM 350-1 parameter assignment tool. Users define encoder type, counting direction, limit values, and output behavior. The count value is transferred to the CPU memory in a dedicated data block. The module includes an interrupt capability to trigger an OB40 upon reaching a limit or after a latch event.
Diagnostics and Mechanical Data
LEDs: SF (group error), DC5V, +24V, and two channel status LEDs for outputs. The front connector is a 40-pin plug (screw or spring type, not included). Dimensions: 125 mm x 40 mm x 120 mm. Operating temperature: 0°C to 60°C. The module draws 75 mA from backplane bus and requires external 24 V for encoder supply (max 300 mA).
