Precision Measurement Engineering, Inc.
|
|
The Self Contained Autonomous MicroProfiler (SCAMP) is a portable, lightweight microstructure profiler designed to measure extremely small scale (order 1 mm) fluctuations of electrical conductivity, temperature, and oxygen concentration in lakes, reservoirs, estuaries, and the oceans. These data can be used to infer the levels of dissipation of turbulent kinetic energy; in-situ fluxes of heat, salt, and oxygen; and the microstructure behavior of these parameters. The SCAMP is waterproof, battery operated, capable of autonomous or on-line operation, and can easily be deployed by hand from a small dinghy. It is equipped with sensors that feature high spatial resolution and fast-time response. The unique drag plate and floats allow the SCAMP to ascend or descend vertically making measurements (1 scan of all sensors every mm) through undisturbed water. This allows the user to measure properties in the surface layer (ascent) or the benthic boundary layer (descent). The software supplied with the SCAMP allows the user to upload, record, view, and analyze measurements. The new improved SCAMP now has a USB interface. For more information read the USB manual. For information about the first generation SCAMPs read the manual. The SCAMP is designed to profile water columns of up to 100 meters in length, sampling all sensors every 1mm. The SCAMP can sample while traveling at 10 cm/sec either upward or downward through the water column. If the SCAMP is used in downward mode, then it can sample undisturbed water beginning somewhat below the surface and continuing all the way to the bottom. In upward mode, it can sample undisturbed water up through the surface. These two modes of travel enable the SCAMP to measure both surface mixing and benthic boundary layer mixing. The following photos show the SCAMP's position in the water for each mode.
 
UPWARD These images show these features: the floats are shown above the
hand, the drag plate is shown below the hand. Note that this plate is shown at a slight
angle from perpendicular to the SCAMP body. The plate is hinged on the supports and it
will swing up to 30 degrees. This causes the SCAMP to sink sideways. On ascent, the plate
swings to the perpendicular position and the SCAMP floats straight up. There are two arms
on the release plate, held together by a pin (not shown). The pin is attached to the
retrieval line. This pin pulls away during retrieval and the sides of the drag plate fold
away for easy towing through the water.
ANALOG PROCESSING In addition to the sensor electronics and the A/D converter, the SCAMP contains two types of analog processing circuits: offset-gain scaling and gradient-gain-filtering. An offset-gain block is connected between sensor channels and the A/D converter. This block has the effect of allowing the SCAMP's A/D to sample a sub-range of the sensor range under software control. For example, the temperature sensor's electronics has valid output for the range 0 to 30 deg. C. Under software control, the offset and gain block can be programmed such that the A/D's full range occurs over the temperature range of 10 to 15 deg. C, giving 6X resolution. Sub-ranging can also be applied to other channels. The SCAMP can support up to 8 gradient-gain-filter blocks. These blocks first compute the time derivative of a sensor channel, then amplify the result by a programmable gain of 1 to 256, then filter using a 6-pole anti-alias filter at a fixed frequency of 45 Hz. These circuits can be connected to any channel, but usually are connected only to the fast temperatures. These channels have the effect of eliminating A/D noise since the gradient signals are zero mean and can be amplified significantly. The paramount design criteria in both the SCAMP's electrical design
and mechanical packaging is to obtain a measurement system designed for spectral analysis
and having the lowest measurement noise possible. The SCAMP is supplied with software that enables control of the SCAMP, calibration, data acquisition with upload to host computer, complex analysis, and graphical display. This software runs under Windows 2000. Control of the SCAMP includes many items related to the SCAMP's internal state such as measurement of battery voltages, various tests of analog and digital hardware, time keeper control, and other housekeeping functions. Data acquisition and upload are managed by SCAMP's internal computer based on information provided by host computer software. The customer may set data acquisition start/stop parameters such as depth, time, or number of samples by using menus provided by the host computer software. Subsequently when measurements are completed they appear in internal memory buffers within SCAMP. Matlab software supplied with SCAMP allows the customer to save the measurements on disk for later viewing or analysis. Matlab can perform various types of complex analysis of SCAMP measurements. The software can:
Graphical display is an integral part of the calculations mentioned above. Each calculation has a representative display, often shown as the calculation result vs time or depth over full profiles or user-selected profile sections. The screen below shows a full profile at left of the (computed) Sigma-T channel measured by the SCAMP. The dotted lines indicate the segment selected for spectral analysis and Batchelor fitting. The center plot shows the Gradient Fast T0 channel, segment 9 of which (dotted lines) is analyzed and presented in the right two plots. The top right plot shows the matching of the observed power spectrum of Gradient Fast T0 (blue) to the ideal Batchelor spectrum (red) plus the anticipated electronic noise of SCAMP’s sensors and circuits (green). More detailed information about the methods used to obtain these plots is given by the first two entries in the references section below.
The screen above is representative of the various screen plots that Matlab software can display. Matlab software displays are available within a very short time after uploading the SCAMP measured data. It is possible to know the turbulent state of a profile in nearly real time. The intent and design of the Matlab software are to allow easy control of SCAMP and to allow the customer to visualize the processes occurring within the water column in nearly real time. This enables the scientist to make sampling decisions based on conditions presently occurring within the water column, and is a powerful tool for the educator to provide motivation for students of environmental fluid dynamics. For more information read the USB manual.SPECIFICATIONS
PRICE LIST (subject to change without notice)
SCAMP accessories included with the profiler are:
Various other sensors can be mounted on the SCAMP. Contact PME regarding special projects. The following references describe the SCAMP or related instruments and measurements. Anis, A. (2006), Similarity Relationships in the Unstable Aquatic Surface Layer, Geophys. Res. Lett., 33, L19609, doi:10.1029/2006GL027268. View the abstract. Anis, A; Singhal, G. (July 2006), Mixing in the Surface Boundary Layer of a Tropical Freshwater Reservoir, Journal of Marine Systems, doi:10.1016/j.jmarsys.2006.07.003. View the abstract. Chen, Huey-Long; Hondzo, Miki; Rao, A. Ramachandra (Dec., 2002). Segmentation
of temperature microstructure, Journal of Geophysical Research-Oceans, 107(C12).
Internet listing - http://www.agu.org/pubs/inpress.html Imberger, J. and Ivey, G.N. (1990). On the Nature of Turbulence in a Stratified Fluid. Part II: Application to Lakes. J. Physical Oceanography, Vol. 21, pages 659 to 680. This paper (together with Part I) is the fundamental work upon which SCAMP is based. View the abstract in Adobe format. Ivey, G.N., and Imberger, J. (1990). On the Nature of Turbulence in a Stratified Fluid. Part I: The Energetics of Mixing. J. Physical Oceanography, Vol. 21, pages 650 to 658. This paper (together with Part II) is the fundamental work upon which SCAMP is based. View the abstract in Adobe format. Krocsis, O., Prandke, H, Stips, A., Simon, A., and Wuest, A.(1999). Comparison of Dissipation of Turbulent Kinetic Energy Determined from Shear and Temperature Microstructure. J. Marine Systems, Vol. 21, pages 67-84. This paper presents an excellent comparison of the Batchelor temperature microstructure method with the velocity shear microstructure method for determining turbulent dissipation. Luketina, David A. and Imberger, Jorg (1998). Determining Turbulent Kinetic Energy Dissipation from Batchelor Curve Fitting. Submitted to the J.. Atm. and Oceanic Tech. This paper presents a method for fitting temperature gradient spectra to the Batchelor form. View the abstract or the complete paper in Adobe format. MacIntyre, Sally (1998). Turbulent Mixing and Resource Supply to Phytoplankton. Physical Processes in Lakes and Oceans Coastal and Estuarine Studies Volume 54, pages 561-590. This paper presents an example SCAMP use. View the abstract in Adobe format. MacIntyre, Sally, Flynn, Kevin M., Jellison, Robert, and Romero, Jose R. (1999). Boundary mixing and nutrient fluxes in Mono Lake, California. Limnology and Oceanography, Vol. 44, #3, pages 512 to 529. This paper presents an example SCAMP use. View the map of Mono Lake and the complete paper in Adobe format on Sally MacIntyre's web site. Nash, Jonathan, and Moum, James (1997). Estimating Salinity Variance Dissipation Rate from Conductivity Microstructure Measurements. J. Atm and Oceanic Tech. Vol. 16, #2, pages 263-274. This paper presents data analysis based on the Fast C sensor mounted on another instrument. Piera, J., Roget, E., Catalan, J., 2002. Turbulent patch identification in microstructure profiles: A method based on wavelet denoising and Thorpe displacement analysis. J. Atmos. Ocean. Tech. 19 (9), 1390-1402. Ruddick, Barry, Anis, Ayal, and Thompson, Keith (1999). Maximum Likelihood Spectral Fitting: the Batchelor Spectrum. This paper presents a method for fitting temperature gradient spectra to the Batchelor form. Submitted to J. Atm and Oceanic Tech. View the abstract or the complete paper in Adobe format. Sharples, Jonathan, C. Mark Moore, Edward R. Abraham (15-Jul-2001). Internal tide dissipation, mixing and vertical nitrate flux at the shelf edge of NE New Zealand. Journal of Geophysical Research, Vol. 106, No. C7, pages 14,069 - 14,081. View the abstract in Adobe format. Soga, L.C.M. and Rehmann, C.R, 2004. Dissipation of Turbulent Kinetic Energy near a Bubble Plume. J. Hydraul. Eng., 130, 441-449. Stevens, Craig, Murray Smith, Alex Ross (1999). SCAMP: measuring turbulence in estuaries, lakes, and coastal waters. NIWA - Water and Atmosphere, Vol. 7, #2, pages 20-21. View the complete article in Adobe format.
|
