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Series Overview

M90/M91™ : micro PLC with text HMI

The M90/M91™ is an innovative micro-PLC (Programmable Logic Controller) with a built-in operating panel. The operating panel offers an LCD that can display two 16-character text lines, and a keypad (one line in the M90 models). The M90/M91™ series offers a variety of onboard I/O configurations, including direct temperature and weight measurement inputs; the configuration can be expanded by adding I/O Expansion Modules. The M90/M91™ is the perfect control solution for small-to-medium applications such as water treatment, automated machines, and process control.

Our PLC/HMI integrated devices:

  • save our customers’ programming time, wiring, and cabinet space
  • cut budget by reducing requirements for additional hardware
  • prevent you from wasting time setting up Panel-PLC communication


  • Up to 38 onboard I/Os: Digital, Analog and temperature measurement inputs, Relay or Transistor outputs
  • Shaft encoder inputs and PWM outputs
  • I/O Expansion Modules: enable up to 96 digital I/Os plus additional analog, temperature and weight inputs (number/type vary according to model)
  • RTC, enabling time-and-date controlled operations
  • 24K-36K (virtual) Ladder code capacity
  • Functions include: math, store/load, compare, and clock functions, plus immediate read/write to I/Os, interrupts and loops
  • 1K database
  • 4 PID loops including auto-tune
  • Mounting: Panel or DIN-rail


  • Two 16-character text lines, LCD illuminated screen
  • Alphanumeric 16-key keypad, for data entry and to initiate tasks
  • Multilingual display- supports over 15 languages
  • Up to 80 user-designed screens, displays conditional messages
  • Display conditional text, time, date, bit status, timer & integer values (up to 64 HMI variables per application)
  • “List” variables: link up to 150 messages to a single variable, to add 2K’s of conditional text. “List” variables allow easy scrolling between recipes/menus via the keypad
  • Info mode: view I/O status, integer values, and system data on the LCD display


  • RS232 or RS232/RS485 serial communication port
  • GSM/SMS support
  • Remote access via network GPRS, GSM, CDMA or landline modems
  • Data Export to/from Excel
  • MODBUS (master/slave)
  • CANbus port (model dependent)
  • OPC/DDE server

Our HMI/PLC programming software and software utilities are free to all Unitronics clients.

Technical Specifications