SM4: Sediment transport measurements with conditions based monitoring
The forth generation SediMeters™ add nephelometric turbidimeters and an accelerometer to the sediment level sensor
The SediMeter can be used to get quantitative data on the dynamics of the sea floor with high temporal resolution, such as for monitoring sediment spill from dredging in real-time. SM4 also has dual nephelometric turbidimters (ISO and EPA), plus an accelerometer for tilt, vibration, and conditions based monitoring (CBM).
Imagine an instrument that detects when something unusual happens, such as being run over by a turbidity current, or experiencing an earthquake, and which starts measuring when that happens. The forth generation SediMeter has that ability. The accelerometer is programmed to trigger an extra measurement for every strong acceleration event, once mounted.
The "color SediMeter", new for 2017, measures both straight and oblique backscatter, giving a false color image with 5 mm resolution. It measures a 35 cm long vertical profile of turbidity at 71 levels using 36 near infrared optical backscatter detectors, 1 cm apart. Brown to beige tones denote buried detectors, while those exposed to air become blue.
SediMeter™ model SM3A mounted in Biscayne Bay.
The SM4 instruments measure 20 or 30 acceleration values for each of the 3 axes in every measurement, with 12 or 8 bit resolution, respectively. The standard frequeny is 10 Hz, but it is possible to measure at a frequency from 1 Hz to over 5 kHz. By adjusting the filter and threasholds it is possible to target extra measurements in conditions-based monitoring to the desired type of event, such as vibrations due to strong currents; being hit by an object such as a log; or specifically to seismic events, to name some of the possibilities.
Model SM3B has a built-in mechanical cleaner (left). Model SM3A has a diameter of only 15 mm (right). The SediMeters offer several deployment options. All SediMeters can be used both as stand-alone loggers and connected by cable.
By measuring turbidity every 5 mm, in two different ways, and presenting the data as a color plot, the ability to discriminate between different targets improves, such as between different grain sizes, between solid bottom and fluid mud, or between wet sand and air (at night; sunlight prevents reliable measurements).
SediLink™ radio modem
A SediLink™ radio and cell phone modem (pdf) can be used to replace cable. It has a recheargeable battery, and a built in solar panel to charge itself and the connected SediMeters. It also has white blinking lights to alert seafarers about the buoy. The SediLink™ has a socket for an X-Bee radio, allowing a choice of inexpensive radio depending on the need for range, and the local regulations. It mounts on top of a tube with the cable through the tube and down to the instruments on the bottom. It can be used anywhere that X-Bee radios are sold: North and South America, Europe, Australia, and so on. In the U.S. it can also be used as a cellular phone modem. Contact us for a quote.
The SediLink™ radio modem mounted on a buoy.