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Can we set the sample averaging duration?


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  • Official comment
    David Velasco

    That's a good question, Matthew!  The short answer is "no".  A core concept of the Eco--what allows it to be so user friendly--is that the instrument self-configures.  This covers selections that would normally apply to ADCPs, such as depth cell size, averaging times, etc.  But the self-configured averaging interval never falls below about 70 s, so that shouldn't be a problem in your case.

    Note that you CAN configure the Measurement Interval (in fact, you HAVE to).  Then for every Measurement Interval, the Eco figures out the height of the water column, and from there the size of each depth layer and then the number of pings (i.e. the Averaging Interval) required to reach a horizontal velocity precision of 1 cm/s or better.  So the length of the Averaging Interval is constantly changing as a function of depth.  To give you some rough numbers, when in more than 5 m of water, the Eco will ping continuously for about 100-140 seconds.  Some exceptions to this are when you are in very shallow water (say, less than a couple of meters) and/or when going for the shortest available Measurement Interval of 2 minutes.  In these cases the precision will go slightly above 1 cm/s, so if you are ever in these conditions, it's generally better to have longer Measurement Intervals (say, >= 5 minutes).

    And for a fun (although inaccurate) way to see the length of the averaging interval, just look at how long the light blinks after you start up data collection.  The only problem is that, for you to see the true length, you have to be underwater :-)

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