Monthly Archives: January 2017

Color SediMeter Plot

Starting in 2017 all SediMeters measure the turbidity by two different methods, straight and oblique backscatter. This has two effects, first an increase of resolution to 0.5 cm, and second that there are two kinds of measurements that behave in different ways in some cases: When it comes to measure moderate levels of turbidity they will give near identical readings, but when the sensor is blocked by the bottom they may differ a little, and when exposed to air, they will differ a lot. By plotting the two channels in color, as if it were a color photo, we create a color image with 0.5 cm resolution.

The color plot is created from the raw plot in an analogous way to how a color image is created from the raw sensor data. This creates a two-channel image with 5 mm resolution, where straight backscatter is represented as yellow and oblique backscatter as blue. A big advantage of this is that air becomes clearly identifiable since it becomes blue.

The color plot is created from the raw plot in an analogous way to how a color image is created from the raw sensor data. This creates a two-channel image with 5 mm resolution, where straight backscatter is represented as yellow and oblique backscatter as blue. A big advantage of this is that air becomes clearly identifiable since it becomes blue.

New SediMeter shakes itself clean

The SediMeter instrument measures a vertical turbidity profile through the bottom of lakes, rivers, or the sea, in order to monitor sedimentary processes. Since it uses light (near infra-red) it has to stay reasonably clean to function properly, something that can be a challenge in some environments. For that reason we have version SM3B with a built-in mechanical cleaner. Apart from being costly, this has the disadvantage of creating a possibility for failure, by having a moving part in a liquid that sometimes is full of suspended sand particles. A method of keeping clean without moving parts is needed.

The SM3C model that we now announce has a vibrator — as in a mobile phone — that shakes briefly but intensely at preset intervals. The video shows the effect: particles and bubbles dislodged from the sensor.

Notice how the shaking helped dislodge particles the first few times, and a bubble that appeared after rotating it (the white field). Also notice that the resolution is now 5 mm instead of 10 mm, enabling the detection of the narrow dark sediment layer in the test tank. Click for full resolution.

Notice how the shaking helped dislodge particles the first few times, and a bubble that appeared after rotating it (the white field). Also notice that the resolution is now 5 mm instead of 10 mm, enabling the detection of the narrow dark sediment layer in the test tank. Click for full resolution.

Another novelty of 2017 is that we are doubling the resolution by measuring both straight backscatter and oblique backscatter. We will return to that topic in a later post since it has wide-ranging implications for the usefulness of the instrument.

By measuring both the oblique backscatter and the straight backscatter, the effective resolution has been increased from 10 mm to 5 mm.

The effective resolution has been increased from 10 mm to 5 mm by measuring both the straight and oblique backscatter. In a later post we will explain how those striations you see can help you interpret the data.

Much more to come in 2017, never before have we have so many new features in the pipeline!