[CA] Airmar Smart Sensor w/ Axiom 9

[Chuck - Raymarine - Moderator]

David,

It appears that the prior owner/installer has interfaced the Smart transducer (possibly one of Airmar's products) as a NMEA 0183 sensor. The Smart transducer appears to be powered by the MFD's SeaTalk/Alarm port ... this it ill advised, as the MFDs SeaTalk port was designed to supply only sufficient power to quickly interface the MFD to a GPS sensor in very small systems. The NMEA 0183 output of the Smart transducer is then supplying depth data to the MFD. I suspect that if you examined the NMEA 0183 buffer (received sentences only) via the MFD's Diagnostics feature, you will find that the reported fluctuations are present in the data being transmitted by the Smart transducer to the MFD. You may want to instead try powering the Smart transducer from a switched 12VDC power circuit to determine whether the problem persists.

Another possibility is that there are two depth sources within the system ... not supported by this generation of product. In such cases, one of the depth sources would need to be disconnected. You may test for a second source by simply unplugging the MFD's NMEA 0183 cable ... should the MFD continue to report a value for depth after a few minutes, then there is indeed a second source of depth data within the system.

Additionally, should I not have already stated it, the boat must be located in the water when evaluating performance of depth transducers. These transducers were designed to transmit/receive through water, not through air.