The Emerson VersaMax Micro 23 is a mid-range compact PLC that combines 13 discrete inputs and 10 discrete outputs with built-in analog I/O — two 12-bit analog inputs (0–10VDC, 0–20mA, 4–20mA) and one analog output — making it suitable for small machine and process control applications that need both digital and analog signal handling from a single base unit.

What distinguishes the Micro 23 from other Micro models?

The Micro 23 is the only VersaMax Micro model with built-in analog I/O — the Micro 14, 40, and 64 provide discrete I/O only with analog capability available through expansion modules. This makes the Micro 23 a natural fit for applications with a handful of analog sensors (pressure transmitters, level probes, temperature transmitters) that would otherwise require a separate expansion unit. Dual serial ports — RS-232 (RJ-45) and RS-485 (DB-15) — support simultaneous connection to an HMI and a Modbus RTU SCADA network. Battery-backed RAM and real-time clock preserve data and timestamps across power cycles.

What expansion and programming options are available?

Up to four expansion modules can extend the Micro 23 to 135 I/O points — adding relay outputs, RTD/thermocouple inputs, high-speed counters, or additional analog channels. Programming is in ladder diagram or instruction list via Emerson's Machine Edition software (VersaMax Pro). The controller executes at approximately 1.0μs per Boolean instruction with a 1.1ms/K scan rate. Four 10kHz high-speed counters and four 5kHz PWM/pulse-train outputs handle basic positioning and frequency measurement tasks. Modbus RTU master/slave, SNP slave, and serial I/O protocols are supported. Note: online program editing is not supported on the Micro 23 — that capability starts with the Micro 40.