The S4 Current Meter can be configured with optional sensors that allow it to operate as a multi-use platform for operations requiring data acquisition of Currents, Waves, Tide, CTD, turbidity and more. The S4 can also provide current profiling in conjunction with many of the optional sensors available.

The standard S4 includes 64K bytes of memory expandable to 1M byte. The S4A includes 20 Megabytes of memory. The S4AH samples the current vectors and analog parameters at 5 Hz.

Options for additional parameters include: Tilt (mooring inclination and current velocity correction), Conductivity (salinity), Temperature, Depth, Optical Back Scatter (suspended solids), Transmissometer (turbidity), Dissolved Oxygen, pH and other water quality sensors.

S4 Mooring Tripod
Click here for PDF brochure (87KB)

Multi Mode 0peration
The S4A provides for two completely autonomous sampling cycles operating in the same instrument simultaneously. This true multitasking allows one instrument to collect data that normally requires several instruments running different cycles. Each "mode" allows for complete and unlimited control of Sample Period, Average Period (continuous or cyclic) and Parameters to record. All of the sensors available on the S4 can be programmed to sample in either or both of the chosen sampling modes.

Adaptive Sampling
The Adaptive Sampling option permits the investigator to program the instrument to only save to memory events exceeding a preset threshold. This features in the S4 allows burst mode recording of data over extended periods previously not possible due to memory limitations with normal burst mode recording. This has particular application for current and wave data recording where the user is only interested in recording high level occurrence events.

Directional Wave
The S4DW senses wave orbital current components and the 0-70 meter hi-resolution depth sensor provides 4 mm depth resolution for use in wave and tide analysis. The S4 can be easily moored to existing platforms, used in taut-line moorings or bottom mounted. The instrument can provide for real-time measurement or internal data storage with up to 20 megabytes (7 million samples) of solid-state, non-volatile memory.

The S4 samples at a 2 Hz (0.5 sec.) rate. The recorded current vector averaging rate and depth sampling rate can be programmed as a multiple of the 2 Hz rate. For special applications a 5 Hz sampling rate can be provided in the S4AH for improved resolution of shorter wave periods.

Directional Wave analysis is performed by InterOcean PC based "WAVE for Windows" analysis software using the pressure and current velocity data from the S4DW instrument. The wave statistics are calculated by converting the pressure time series and orbital velocity components to the frequency domain using a Fast Fourier Transform (FFT). Once in the frequency domain the pressure amplitude data is corrected for attenuation versus frequency and depth. The direction of the waves is computed using the North and East orbital velocity vectors with auto and cross spectrum analysis of the time series.

With the InterOcean systems "WAVE for Windows" applications software and data from the S4DW in the Directional Wave configuration, the user can process and display all the parametric data for wave analysis. The Graphic and Tabular output includes:

• Max Wave Height
• Average Wave Height
• Significant Wave Period
• Wave Energy as a Function of Wave Frequency
• Wave Direction as a Function of Wave Frequency
• Period of Peak Energy Density
• Average Zero Crossing Periods
• Average Wave Crest Period
• Mean Water Depth

The S4 Family of Instruments and the available Sensors/Parameters are described below. For additional information on utilizing the S4 for wave and tide measurements, see also the Wave & Tide Gauge page.