HART: No Reply Siemens — HART communication impossible (no response from transmitter)
At a glance
- Severity
- WARNING
- Domain
- INSTRUMENTATION
- Reference standard
- IEC 62591 / HART Communication Protocol Rev.7
- Product / context
- HART communication failed — SIMATIC PDM / SITRANS
What it means
The HART communicator (handheld or software) cannot establish communication with the field transmitter. The instrument does not respond to HART polling, preventing remote configuration, advanced diagnostics, and secondary variable readout. The 4-20mA signal may still be functioning correctly.
Probable causes
- Insufficient loop load resistance for HART modulation: a minimum of 250Ω is required between the transmitter and the power supply.
- HART communicator cable not connected at the correct loop point (must be in parallel with the load resistance).
- Transmitter with HART communication disabled or polling address changed (different from 0 in point-to-point configuration).
- Interference from filters or barriers in the loop that attenuate the HART signal (1200/2200 Hz).
Where to start
Verify that the HART communicator is connected at the correct loop point: in parallel with the load resistance (across the PLC analog input or across a dedicated 250Ω resistor). Is the connection point correct?
Full guided diagnosis in the app
The diagnostic tree for this fault has 9 guided steps with measurements, checks and resolutions. You'll find it in ElectraIQ, one of the five IndexOS apps: free, works offline.
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The same fault on other brands
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