Calibrating and Trimming Instruments via HART Agenda: What is HART? / History / Signal / Message Frame HART Command Structure Connecting a HART Transmitter Trimming Devices Trimming Conventional Transmitter vs. HART Transmitter Live Demo
What is HART? HART = Highway Addressable Remote Transducer A digital communication protocol designed for industrial process measurement applications. Uses a low-level modulation (FSK) superimposed on the standard 4 to 20 mA current
HART History RevisionYear x1989– still delivered today – never introduced – introduction of HART wireless
HART Signal
HART Message Frame
HART Command Structure Three levels of commands Universal commands Common practise commands Device Specific commands Universal commands Model ID Tag ID Description Message Date Range Values Instrument Limits Process Measurements Device Status Common practice commands Read Variables Calibration (zero, span) Initiate Self Tests Serial Number Time Constant Values Device Specific commands Model Specific Functions Start, Stop, or Clear Totalizer Select Primary Variable Special Calibration Options PID - SP, Tuning, Etc.
Connecting a HART Transmitter Point-to-point 24V supply + _ Resistor Transmitter HART Communicator mA Polling address = 0 ! => HART + mA signal HART
Connecting a HART transmitter Multidrop 24V supply + _ Resistor Transmitters (max 15 pcs), fixed 4 mA current, Only PV output, different addresses (not 0 !) HART Communicator 4 mA (fixed)... Addr=1215
Trimming Devices CommunicatorsSmart Calibrators
MC5 Internal Connections 24V supply + _ Resistor Transmitter HART Communicator mA MC5 +24V Ground HART
HART vs. Conventional Transmitter (1of 2) Conventional transmitter Input4 … 20 mA Adjustments: Zero Span
HART vs. Conventional Transmitter (2 of 2) HART transmitter Input mA Digital trimAnalog trim Range Transfer Function PV Input sectionOutput sectionConversion AO A/DD/A
Live Demo Presented by: Ned Espy – Consulting Director Beamex, Inc. Office: Mobile: