AML Oceanographic Micro SVP, Руководство пользователя

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User Manual for AML Oceanographic’s Micro SV & P Sensor
8
3 DESCRIPTION
3.1 FUNCTIONAL DESCRIPTION
The Micro SVP Sensor has two separate sensors, refer to
Figure 3.1
, each of which
responds to a specific property of the water environment. The sound velocity sensor
measures the transit time of an acoustic pulse across a fixed distance. The pressure
sensor responds to pressure by monitoring the stress on a silicon chip exposed to the
ambient pressure. The silicon chip is fabricated as a Wheatstone bridge and the
differential voltage output across the bridge is a function of the stress exerted by the
ambient pressure.
SV. Digital
Electronics
SV. Analog
Electronics
P. Digital P. Analog
Electronics Electronics
Power
Additional Sensor Channels
Data
Logger
+
Control
Power
Electronics
Signal Bus
Interface
Electronics
- RS 485
- RS 232
- TTL
Power
Signal
Optional
Battery Pack
Power
Signal
Power
SV
Press.
Sensor
Sensor
Figure 3-1
Micro SVP Sensor Block Diagram
Each sensor requires an excitation signal and synchronous sampling of the sensor output
voltage. The sound velocity and pressure sensors incorporate thermal compensation. The
output voltage must be converted to a digital signal (raw output) and then the calibration
coefficients must be applied to calculate the output in engineering units. All of these
requirements are controlled by a dedicated microprocessor for each sensor. Each sensor
has a dedicated electronics board to provide this functionality. Each board is composed
of an analog section and a digital section. Refer to
Figure 3.1
.
All of the sensor boards, including any additional sensors, plug into the data logger board.
The data logger has a common signal bus for communicating with the sensor boards and
individually controlled power supplies to each of the primary sensors. A microprocessor
on the data logger board controls all the communications and power to the sensors,
collates the sensor data with a date/time stamp and supply voltage, stores the data to flash
memory if required, and outputs the data to the external world via the communications
board.
The communications board converts the incoming commands from, and the outgoing data
to, the chosen external communications format. The standard external format is RS-232C
ASCII, which is also the standard serial communications protocol for personal computers.