Siemens 6ES7350-1AH03-0AE0 FM 350-1 Counter Module for S7-300

The Siemens 6ES7350-1AH03-0AE0 is a FM 350-1 counter module for the S7-300 series PLC. It provides one high-speed counter channel that accepts signals from incremental encoders, proximity switches, or other pulse sources up to 40 kHz. This module is designed for precision position and speed monitoring in industrial automation systems.

Counter Specifications

The 32-bit counter can be configured for up/down counting, single phase (pulse/direction), or two-phase (A/B quadrature with 4-fold evaluation). Maximum input frequency is 40 kHz (5V differential) or 20 kHz (24V). Count range is -2,147,483,648 to +2,147,483,647. Two built-in comparators (high and low) can trigger outputs when limits are crossed.

Input Circuitry

The module accepts three types of input signals: 5V RS-422 differential, 24V DC single-ended, or NAMUR (sensor). Inputs are electrically isolated from the backplane (500V). The module includes a built-in 24V DC sensor supply (max 0.2 A) for powering external encoders. An input filter (0.1 ms to 5 ms) reduces noise.

Outputs and Interrupts

Two digital outputs (24V DC, 0.5 A) are available, which can be set or reset based on the counter value compared to reference values. These outputs can also be controlled by the user program. The module generates hardware interrupts for zero crossing, overflow, underflow, or comparator hits, enabling fast reaction without CPU scanning delay.

Configuration and Programming

Using STEP 7 (TIA Portal or Classic), the module is configured via a parameter assignment screen. Users select counter mode, input type, counting direction, and output behavior. The module provides a dedicated data block for accessing the counter value, status, and diagnostic information. Functions for reading/writing the counter and reference values are included in the standard function library.

Diagnostic Features

Status LEDs indicate power, counter active, output status, and error (wire break, encoder short circuit). The module can report sensor supply faults to the CPU. It also performs a self-test at startup, checking memory and input circuits.

Mechanical and Environmental

Dimensions: 40 x 125 x 120 mm. Weight 0.3 kg. Operating temperature: 0°C to 60°C; storage: -40°C to 70°C. It mounts on a DIN rail and requires a 24V DC supply from the backplane (100 mA) plus external sensor supply. The front connector is a 40-pin screw terminal.

Applications

Typical uses include length measurement on continuous webs, rotational speed monitoring on motors, part counting on conveyors, and position feedback for cut-to-length machines. The 40 kHz speed handles moderate to high-speed applications.

Conclusion

The Siemens 6ES7350-1AH03-0AE0 FM 350-1 counter module extends S7-300 capabilities with high-speed counting. Its encoder compatibility and onboard outputs make it suitable for many motion feedback tasks.