The first SediMeter prototype was made in 1985, a wire-wrapped design using a Z80 processor. After test of concept, a new prototype was developed around the µPD78C05, which was a CMOS processor and thus it was feasible to run it off a battery for months. That model became the first SediMeter to be deployed in the field, in a function test under the ice of Lake Erken, Sweden. It was subsequently used in research in the Baltic Sea, and The Bahamas.
The first commercial version was manufactured in Norway around 1995 to 2005. Then Lindorm, Inc. took over production in Miami, Florida, with the second commercial generation, SM2, which we started developing in 2006. By 2013 we came out with SM3, in which the sensor electronics is identical to that of SM2. We now write 2017, we already have the PCBs for SM4, and once again the sensor electronics is identical to SM2. If it ain’t broken, don’t fix it.
The justification for SM4 is a desire to have higher accuracy in the turbidity measurements of low concentrations. This will be accomplished in three ways:
First, by the addition of ISO-style and EPA-style turbidimeter sensors (replacing the #37 OBS).
Second, by the use of UV light to keep the sensor window clean for those turbidimeters.
Third, by changing the design so that there is no holder tube in front of these turbidimeters, since the holder tube introduces a large amount of reflections, which, even if you correct for them, still drive up the uncertainty to levels that are unacceptable for measurements of dredging spill, for instance.
The SM4 will come in three models, each with its advantages. The SM4C model for instance, will have a 20 mm diameter sensor tube with very thick walls, making it both strong and giving maximal accuracy also for the OBS array of the SediMeter sensor itself. It will also have the larger battery of the SM3B and SM4B mechanical cleaner models, so that it can be deployed for extended periods.
We have today published preliminary specifications, and above you can see the general design of the three models.