YSI ADV6600 - Manual (Page 114)

Section 9. Principles of Operation
ADV6600
Y S I
Environmental
Page 104
Where:
dBar = measured pressure (decibar)
PressOffset = offset calibration constant (decibar)
PressScale = 1
st order calibration constant (decibar/count)
PressScale_2 = 2
nd
order calibration constant (decibar/count
2
)
Counts = measured pressure (counts)
The three pressure calibration constants are measured at the factory and included with each system
(in memory). When using the ADVantage 6600 software to access ADV6600 data files, the
conversion from counts to decibars is done automatically.
9-4.1. Effect of Atmospheric Pressure Variations
The pressure sensors used by the ADV6600 are not vented to the atmosphere. Pressure data may
change with variations in atmospheric pressure. Large atmospheric variations can cause pressure
variations as large as 0.1 to 0.2 decibars. This is equivalent to 10 to 20 cm (4 to 8 in) of water level.
If an external measure of barometric pressure is available, this can be used to correct pressure data
in post processing.
9-5. Temperature
Procedure from Standard Methods for the Examination of Water and Wastewater: 2550
The ADV6600 utilizes a thermistor of sintered metallic oxide that changes predictably in resistance
with temperature variation. The algorithm for conversion of resistance to temperature is built into
the sonde software, and accurate temperature readings in degrees Celsius, Kelvin, or Fahrenheit are
provided automatically. No calibration or maintenance of the temperature sensor is required.
9-6. Conductivity
Procedure from Standard Methods for the Examination of Water and Wastewater: 2510
The ADV6600 utilizes a cell with four pure nickel electrodes for the measurement of solution
conductance. Two of the electrodes are current driven, and two are used to measure the voltage
drop. The measured voltage drop is then converted into a conductance value in milliSiemens
(millimhos). To convert this value to a conductivity value in milliSiemens per cm (mS/cm), the
conductance is multiplied by the cell constant that has units of reciprocal cm (cm
-1 ). The cell
constant for the sonde conductivity cell is approximately 5.0/cm. For most applications, the cell
constant is automatically determined (or confirmed) with each deployment of the system when the
calibration procedure is followed. Solutions with conductivity of 1.00, 10.0, 50.0, and 100.0