…Wherein we learn about product development and get to meet some new employees
(Part III can be found here)
A summer visit from Japan lead to Sequoia’s first distributorship outside the US. Soon, more distributors were signed up in Korea, Taiwan, and other countries. During a visit to the Yangtze River Authority headquarters in China, the director complimented Sequoia with: “You have invented the perfect technology for us. Thank you.” With that, LISST technology was officially approved in China. Outside of the US, China is Sequoia’s largest customer. Thousands of LISST’s are now used on all five continents. Approximately 2/3 of Sequoia’s production is exported and in 2015, Sequoia won the Exporter of the Year award from the US Region-10 Small Business Administration.
With his interest in marine sediment transport, Yogi knew the importance of finding a way to directly measure the size-dependent settling velocity of suspended particles with an extension of the LISST-100. The key here was ‘size-dependence’ in settling velocity. Prior instruments could only obtain a single gross settling velocity for the full PSD. By attaching a Settling Tube to a LISST-100, the LISST-ST was born.
As particles captured in the tube settled, particles of different settling velocities settled out at different times. This was identified from the measured evolution of size-distribution measured by LISST-100 optics. Notably, the size of grains was obtained by their diffraction signature, while their settling velocity was based on how long it took a particular size to settle out. In this way, size and settling velocity were independently measured, avoiding Stokes’ settling formula. This innovation permitted a comparison of measured size-dependent settling velocities with a model for spherical solid particles, Stokes’ Law. Large particles were seen to settle slower than Stokes law. This was attributed to flocculation. The LISST-ST was Sequoia’s second product. Along the way, the company acquired a license for a water level sensor, AQUAROD, later sold to another company.
A group of three highly accomplished persons joined Sequoia in 1996: Dr. Curtis Mobley worked in the field of underwater light propagation. His scientific software was transitioned as a software product HYDROLIGHT. Accompanying him were Dr. Robert Maffione and David Dana. Shortly thereafter, Maffione and Dana left to setup another company in California. In 2013, David Dana returned to Sequoia and is now the VP of Engineering. Dr. Mobley retired from Sequoia in 2018. With the added headcount also the admin staff grew – and what a great looking crew our heroes had assembled towards the end of 1996!
Back row, left to right: Doug Keir, ?, ?, ?, Lino Verna, Yogi Agrawal.
Front row, left to right: David Dana, Curt Mobley, Robert Maffione, ?, Chuck Pottsmith.
In Part V we get an insight into some of the first LISST user workshops in the late 1990’s – there will be more pictures!