A CTD or SV profiler that is not in the field is not earning its keep. Nevertheless, users of oceanographic equipment have been packing up their instruments and shipping them back for annual recalibration for over 50 years. Every ocean-focused organization knows the story of kit made unavailable because of recalibration. It almost always takes longer and costs more than originally expected.
In contrast, field-swappable sensor heads ensure that instruments stay in the field, where they belong. Instead of removing an instrument from a vessel for recalibration, recently calibrated replacement sensor-heads can be sent directly to the ship. Sensor-heads can be maintained in inventory and shipped overnight. Upon their arrival, old sensor-heads are unscrewed from the instrument and replaced by the newly recalibrated sensor-heads.
At the end-user’s leisure, the old sensor-heads are sent back to the factory for their own recalibration. Upon arrival at the factory, they can be recalibrated and returned to the field for use on another instrument. Alternatively, they can be warehoused for future, just-in-time recalibration and delivery.