First Nilsson Samplers ready for delivery

The Nilsson Sampler, also known as the Uppsala sampler, or the Swedish sampler, was designed in the 1960’s for taking vertically integrated suspended sediment samples without bias. The criterion is that the water velocity in the inflow pipe must match that in the surrounding water, and the fill velocity must be constant.

These were made at Uppsala University, Department of Physical Geography, in the Geomorphological Laboratory until the building was torn down. Then the instrument manufacturer continued to make them at his private workshop until 2016. In 2017 we took over the molds and models, and we are now making them in Miami, Florida. The video below shows how they work.

Fourth Generation SediMeter

The SediMeter™ SM4 has the same sensor as SM3 for beload transport, erosion and sediment accumulation; plus nephelometric turbidimeters for suspended sediment transport; plus an accelerometer for detecting energy levels and for conditions based monitoring (CBM); plus UV anti-fouling; plus a fluorescence meter; plus a light meter for good measure.

SediMeter SM4

SM4 has the same SediMeter™ sensor as SM3, plus a thicker section with nephelometric turbidimeters, a fluorescence meter, a light meter, and an accelerometer.

We expanded the top part of the instrument so that it does not enter the holder tube, since the holder tube adds reflections and noise to the turbidimeter measurements. Furthermore, we replaced the #37 optical backscatter detector with not one, but two nephelometric turbidimeters. Nephelometric means that they measure 90º scattered light, meaning that the light exits and re-enters the tube at different points, which further decreases the reflections and signal noise. The result is a SediMeter™ that is not just suitable for studying the sediment bedload, but also for monitoring the suspended load.

We put in both a NIR (near infra-red) nephelometric turbidimeter based on the international standard ISO 7027 (with units FNU), and a white light nephelometric turbidimeter based on the U.S. EPA standard (with units NTU). They are coaxially mounted, meaning they measure the same volume of water. We also added a fluorescence meter that exites at 367 nm and measures visible light (peak 570 nm, 50% sensitivity from 470 to 680 nm). This detector is also used as a light meter. All of these measure at the same location.

Another exiting addition is the accelerometer. Apart from alerting the operator if the instrument has fallen over, it gives information about vibrations. In strong currents (or waves) the instrument will start vibrating due to the creation of vortices. The accelerometer will record this, but moreover, it can alert the CPU and trigger an extra measurement. This conditions-based monitoring (CBM) will enable the SM4 instrument to measure the peak events.

To avoid that the memory gets filled during prolonged vibrations, the threshold is dynamic. When the instrument is deployed the CBM threshold is by default close to the noise level. Thus, even small magnitude events should be picked up. Every time the instrument takes an extra measurement, it raises the threshold for the next CBM event. This should guarantee that the peak event gets captured.

When a measurement is taken the accelerometer data is read from a FIFO (first in first out) cyclic memory. Thus, the CBM measurement includes the accelerometer data that triggered it.

The accelerometer can be set up with different measurement rates, filtering parameters, and threshold, depending on the type of event that the user wants to capture. For instance, by measuring at a slow rate with a low-pass filter, one can target seismic events while ignoring instrument vibrations, and vice versa.

To protect against bio-fouling we added UVA light to the turbidimeter windows. To protect the users eyes while working on the instrument in the laboratory, the UVA cleaning function is only active when the instrument is mounted vertically.

We have also released SediMeter software ver. 4. Flyers, specifications, manuals, and software are available on the downloads page.

Joint Venture

We are pleased to announce that we have entered into a Joint Venture with ProconsultRJ in order to better serve present and future customers in Latin America. For immediate release.

Lindorm Announces Joint Venture with ProconsultRJ

Lindorm, a specialist in sediment process studies and manufacturer of the SediMeter™ monitoring instrument, is entering a strategic alliance with ProconsultRJ to provide services and products to the Latin American market.

Miami, FL, December 12, 2017 — Lindorm, Inc., a sediment specialist and manufacturer of sedimentation and erosion monitoring instruments, is entering a strategic alliance with Proyectos & Consultoría Rotciv Jiménez (ProconsultRJ) of Venezuela, to provide services and products to the Latin American market, for the benefit of engineering projects with issues related to sediments, and to environmental protection projects.

Lindorm will offer scientific expertise as well as the SediMeter™ and other instruments for measuring sedimentation, erosion, and sediment transport, while ProconsultRJ will address civil engineering and logistical issues that arise. Lindorm manufactures the SediMeter™ instruments and exports them globally. Dr. Ulf Erlingsson, owner of Lindorm and inventor of the SediMeter™, is a recognized expert in matters of erosion and sedimentation. Rotciv Jiménez, owner of ProconsultRJ, is a civil engineer with experience in both the private and public sector.

Says Dr. Erlingsson, “To provide better value to our customers we want to offer them services and products that reflect what they need, and this requires a substantial presence in the field, which ProconsultRJ will provide us. Also, ProconsultRJ can take on projects with our backstopping that they might otherwise not have qualified for. This makes it a win-win alliance.”

Rotciv Jiménez and Ulf Erlingsson

Fouling problem solved

Unprotected holder tube (left) compared to tube with 1 inch wide copper tape on reverse side (center) after 8 weeks

The main role of the SediMeter sensor is to measure the bottom level, in order to quantify erosion and sediment accumulation. The SediMeter sensor consists of optical backscatter detectors mounted inside a tube. They emit light through the tube and measure the reflected light. Obviously, the tube has to be reasonably clear for this to function. When the instrument was invented this was not an issue; one could just paint the sensor with transparent TBT-containing anti-fouling paint. However, due to its extreme toxicity TBT has long since been banned (except for in some sensors where it was grandfathered in, but the SediMeter is not one of them). Therefore much of the R&D in Lindorm over the last 10 years has been devoted to finding alternative solutions. The first somewhat workable solution was a mechanical cleaner; however, anything involving moving parts in a liquid full of sand is prone to failure, plus it uses a huge amount of power relative to the rest of the instrument. So we kept looking.

During 8 weeks in May to July of 2017 we deployed two SediMeters with copper tape on the rear side of the holder tube in Biscayne Bay, 1 m depth, next to a reference instrument. Both the taped instruments provided usable data for the entire period. With useable we mean that the bottom level could be determined with confidence. As a comparison, the reference instrument was completely covered in barnacles except for just above the bottom. In fact, the bottom level could be determined on that, too, but it might require more experience. We can therefore say that the fouling problem is solved; however, we will not stop this R&D. We have a new transparent anti-fouling paint to test, and we will continue developing the UV light for protecting the turbidimeters.

After a few weeks the fouling of the copper-protected instruments stabilized as sea urchins regularly grazed the algae.

SM4 Final Design

The new generation SediMeters have finally been born, two months delayed due to a high order volume so we are not complaining. The tentative designs have been adjusted so that the SM4A and SM4C now are identical in all but one aspect: The C model has a much larger battery capacity.

SM4A and SM4C final designs. Click for full size.

Shape: Instead of making the A version 15 mm diameter and the C version 20 mm, we have decided to make both 15 mm in the lower end over the OBS array, and 20 mm in the upper end over the turbidimeters. The OBS array is visible on the drawing as 36 black dots in the narrow portion of the instrument. This allows both models to be mounted in the traditional holder tube, which allows the instrument to be replaced at regular intervals (like every week or fortnight) while the holder tube stays stationary, thus giving a continuous measurement series. This is standard operating procedure in many organizations; they have two instruments for each measurement site, one is deployed and the other is serviced, battery recharged, data extracted, and recalibrated if needed.

Turbidimeters: SM4 has two turbidimeters mounted side by side, so as to measure the same water volume, with the light exiting and entering in the same part of the sensor. One is an ISO style (International standard) with a NIR laser light source, the other is an EPA type (U.S. standard) with a white LED light source. The location of the light sources and the photodetectors is indicated with two pairs of black dots in the drawing.

Ambient light: The visible light photodetector has a spectral sensitivity similar to that of the eye, so it will be calibrated to show light in lux. The caveat is that the sensor is mounted horizontally, so it is not measuring incident light from above but from the side. Still, it gives an idea of the ambient light level. The NIR photodetector is similarly used to measure the ambient level of near infra-red light. The NIR light is absorbed very quickly by water, so if this value is high, the instrument was not submerged.

Accelerometer: The SM4 has an accelerometer that is programmed to continuously measure at a rate of 10 Hz and store the last 32 measurements in a FIFO memory. When a SediMeter measurement is made, most of those data are fetched and stored in the data record. In the PC software the tilt of the instrument is calculated. This is important for users who deploy the instrument attached to a platform lowered from the surface, since it will give them certainty regarding the position of the platform on the bottom. The software also calculates vibration (RMS) and peak acceleration. When a strong current is present the instrument may start vibrating due to vortex formation, why the vibration level indicates the presence and strength of the current (or waves).

Conditions Based Monitoring: The accelerometer measures independently from the processor, and is programmed to set a flag if exposed to certain acceleration events. The thresholds and conditions can be changed from software in expert mode. The purpose of this is to trigger extra measurements based on detected conditions, which could be indicative of an earthquake, a turbidity current, an object hitting the instrument, a ship grounding nearby, etc. To avoid getting too many extra measurements in an ongoing condition, the trig level is increased after each time it has triggered an event. The objective is to capture the largest events during each mission.

UV LEDs: The instruments have two UV LEDs for anti-fouling of the turbidimeter sensors, one where light goes out, one where it comes back in. These are programmed to blink with very strong light at regular intervals, the user decides how often. The 365 nm UV light disrupts organic molecules in organisms, and that has an antimicrobial effect (it also causes cataracts so don’t look at this blinking light for extended times, or at short distance, without UV-filtering eye protection). Remember, you see them as blinking but you only see a few percent of the light; most of the light is invisible and harmful to your eyes! The UV LEDs consume battery when used a lot, which is why the SM3C version has a much larger battery, for longer stand-alone deployments. It has up to 10 times more power available for the UV LEDs.

Fluorescence: One of the UV LEDs can be used together with the visible light photodetector to measure fluorescence. We have not programmed it to do that, but the possibility exists if there is interest from our customers.

SediMeter: Not to forget, the OBS array for measuring sediment level and vertical turbidity profile through the water/sediment interface remains identical to past versions. The sensor measures 36 levels of straight backscatter, and 35 levels of oblique backscatter in between the 36 levels, thus creating a vertical profile 35 cm long with 5 mm resolution. The software can present the straight levels, the oblique levels, both types combined, and lastly, a false color image with 5 mm resolution by combining the two. In false color air becomes blue, sediment becomes beige, and water becomes black or gray depending on turbidity.

Finally, you may notice that the B version is missing in the lineup. The SM4B version has a mechanical cleaner, but based on field tests in Miami the past summer we are inclined to believe that the SM4C is a better choice in fouling environments. The combination of copper tape away from the optical surfaces, and UV LEDs at the turbidimeters, seems enough to keep fouling at bay sufficiently for a successful mission. Thus, the failure risks and complications of a mechanical cleaner can be avoided. We also have another card up the sleeve, a transparent antifouling paint that we are testing. For the time being we are therefore working on alternatives to the mechanical cleaner.

Nilsson Suspended Sediment Sampler back in Production

The depth-integrating sediment sampler developed in Uppsala by Dr. Bengt Nilsson in 1969 went out of production when instrument maker Sören Carlsson passed away in January this year. Since we had an order we started a rescue operation, and went to Sweden to recover the molds and tools. We have now started production in Miami, Florida, and we again accept orders.

Nilsson sampler nozzles

Production of the Nilsson sampler has been resumed, now in Miami, Florida rather than Uppsala, Sweden

The photo shows the new nozzles made for an order from Bhutan, the “Dragon Kingdom” high in the Himalayas between India and China. The sampler, variously known as the Swedish Sampler, the Uppsala Sampler, and the Nilsson Sampler, was developed during the International Hydrological Decade and was adopted by many countries as their standard. We can supply spare parts and replacement parts for these older samplers, as well as completely new samplers.

4th Generation SediMeter in 2017

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.

SediMeter SM4 models

Left, SediMeter SM4A, 15 mm diameter, mounted so the dedicated turbidimeters end up above the holder tube. Center, SM4B, with 20 mm diameter above the holder tube for the cleaner shuttle to work. The connector is in the bottom end since the top is occupied by the cleaner reel. Right, SM4C, with 20 mm diameter all the way and no holder tube (it is attached to the anchor before being deployed).

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.

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!