Water Quality Instrumentation miniDOT Logger Extends Depth Range to 300 M By Kristin Elliott W ater quality monitoring devices that record accurate and reli-able data on dissolved oxygen and temperature are essential in research conducted in both fresh and saltwater. Many loggers are subject to a common limitation wherein readings are not certi ed or reliable past the depth of 100 m. As a result, nding lasting, durable and affordable loggers that can reach greater depths has been challenging. Precision Measurement Engineering (PME) has addressed this challenge through advancements in third-party and in-house testing of its miniDOT logger, which is now veri ed to reach 300-m depth. This triples the device’s original logging limit of 100 m. Design Constructed from durable plastic, the miniDOT log-ger records dissolved oxygen and temperature mea-surements. The sensor uses an optode to measure the lifetime-based luminescence quenching of a thin mem-brane. Operation of the miniDOT, such as setting the time and sample intervals, can be accomplished via USB cable. With a form factor that can t in your hand, the mini-DOT is designed for reliable data collection in rugged conditions. The device size and shape allow for many applications, including in underwater caves, boreholes, wells and open water, to name a few. For longer deployments, the miniDOT is tted with an optical sensor that can hold its calibration for up to one year without researcher intervention. PME’s extensive multi-point calibration preserves logging accuracy over time to provide the best data possible. PME’s sensing foil is located inside the logger itself and does not degrade or require multiple replacement pieces within the same year, saving time and money. Software is provided with every miniDOT and is The miniDOT log-ger has an extended depth range to 300 m. found on the micro-SD card when connected to a com-puter. The software displays les, creates visual plots to read oxygen measurements, and allows the user to set the internal clock and determine a sample rate. New Depths When researchers utilizing the miniDOT logger in numerous projects reported successfully deploying the device at depths in excess of 100 m, PME began reevalu-ating the miniDOT logger’s capacity. Recorded data had already con rmed accuracy beyond the guaranteed lim-it, so with the mindset of expanding product functions, PME began product testing to reach a greater logging range to bene t researchers worldwide. Since launching the miniDOT in 2009, testing pro-cesses and procedures have also advanced to provide a better understanding of product capabilities. Between researcher feedback and advancements in product test-18 ST | February 2023 www.sea-technology.com
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