MicroLink-HM RS-232 is a managed HART modem that can be used as a primary or secondary HART host interface - eliminating the need for external carrier detect (CD) monitoring and request-to-send (RTS) control. It can also be configured to continuously poll up to 16 HART devices, filling internal Modbus registers with variable values.  The variable values can then be read as 16-bit signed integer or single precision floating point using Modbus-RTU commands. Configuration is saved in Modbus registers allowing Modbus commands to be used for configuration - or use the free included HM Configuration app. 

MicroLink-HM RS-232 Manual (PDF)
Quick Start Guide (PDF)
> HM Configuration App
> HART Protocol Host App
Application Note 620-0026 - Using Modbus with the MicroLink-HM (PDF)


  • Can be used as a standard HART protocol modem or HART to modbus accumulator

  • DIN Rail Mounted (35mm)

  • Powered from the RS-232 port DTR line or external 5 to 30 Vdc supply

  • LED provides HART communications status

  • Compatible with USB to serial converter cables

  • RS-232 port can be set to standard baud rates from 1200 to 57600 O, E, N parity

  • Complies with HART physical layer

  • Transformer isolation simplifies loop connections and eliminates grounding effects

  • Use standard modbus commands to read HART device variable data

  • Includes HM Configuration app

  • Includes Microflex HART Host 3B app (60-day trial)