Siemens 6ES5240-1AA21 Counter Module

This module captures high-speed pulse signals from encoders and sensors. The Siemens 6ES5240-1AA21 processes up to 10 kHz input frequency with precision. It measures 232 mm in width and 75 mm in height. This unit weighs approximately 0.48 kg for standard rack mounting.

Technical Specifications Table

Parameter	Value
Product Model	Siemens 6ES5240-1AA21
Category	Counter Module / Position Encoder Input
Input Channels	2 independent counter channels
Max Input Frequency	10 kHz per channel
Counter Resolution	16-bit (0 to 65535 counts)
Dimensions (W x H x D)	232 mm x 75 mm x 130 mm
Weight	0.48 kg
Signal Input Type	24 V DC, optically isolated
Connector Type	1 x 20-pin female front connector
Internal Components	2 x 16-bit counters, 1 x quartz oscillator
Energy Storage	None (volatile counters lose data on power loss)

Internal Design and Signal Processing

This counter module uses two independent 16-bit hardware counters. A quartz oscillator provides the internal time base for accurate counting. The Siemens 6ES5240-1AA21 accepts 24 V DC signals from incremental encoders or proximity switches. Each input channel features optical isolation for noise immunity. The module stores no energy for counter retention after power-off. Therefore, you must save critical counts in your PLC program.

Installation and Wiring Guide

First, mount this module into any S5 rack slot except the CPU slot. Next, connect your encoder signals to the front connector pins 2 and 3. Then, wire the 24 V DC supply to pins 1 and 20 for the input circuit. The module requires a minimum 5 ms pulse width for reliable detection. You can configure each channel for up, down, or bidirectional counting. This module works with all SIMATIC S5 CPU models from 95U to 155U.