Emerson Exchange 365

[026 - Sensor Comm. Fail] alarm persist days after replacing 2700 with 5700 on a CMF300M356NABZEZZZ

Hi Team,

We encountered frequent alarms on a CMF300 with a recently replaced TX from 2700 series to a more modern 5700 series.

It was reported that weeks before the transmitter replacements on the CMF300 sensor, this alarm was long observed and not acknowledged.

However, after the replacement of the 2700 transmitter with a 5700 transmitter on the same CMF300, the alarm  error message was found to still persists. [026 - Sensor Comm. Fail]

On recycle and power on, the core processor LED remains OFF instead of being ON.

it appears the coriolis sensor is not communicating with the transmitter.

Further troubleshooting showed communication from the transmitter to SCADA is okay.

Simulation results are also good.

My Suspicion is on the core processor which i think could be faulty. what do you guys think?

Advice if this issue is only about the core processor which needs to be replaced.

• Coriolis Flowmeters

okpako

• 27 Feb 2026 9:20 PM
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1 Reply

• Jared Drennen

  

  • 2 Mar 2026 4:20 PM

  I agree with your assessment. If the core processor is not powering on (i.e. no LED lights), even with a new transmitter, then I suspect bad wiring from the transmitter, or a bad core processor. Replacing the core processor would be step 1. However, if the core was damaged due to a power surge that damaged the original transmitter, there may be other issues with the sensor. Since you're removing the core processor anyway, I'd recommend taking resistance measurements from the feedthrough pins underneath to confirm continuity in the drive, pickoff, and RTD circuits. Please refer to Sections 17.15 and 17.36 of the 2700 Config & Use Manual: www.emerson.com/.../manuals-guides-5700-transmitters-configurable-outputs-micro-motion-en-66514.pdf. All further questions can be directed to [email protected] (1-800-522-6277).

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