YSI Professional Plus - Manual (Page 21)

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Highlight Calibration Value and press enter to
manually enter the correct “true” barometric
pressure. Next, highlight Accept Calibration,
and press enter. If User Field 1 or 2 are enabled,
you will be prompted to select the fields and
then press Cal
to complete the calibration
or press Esc to cancel the calibration.
Laboratory barometer readings are usually “true”
(uncorrected) values of air pressure and can be used “as is”
for barometer calibration. Weather service readings are
usually not “true”, i.e., they are corrected to sea level, and
therefore cannot be used until they are “uncorrected”. An
approximate formula for this “uncorrection” is below:
true BP = [Corrected BP] – [2.5 * (Local Altitude in ft. above sea level/100)]
conductIVIty
Conductivity sensors are supplied with 60530-X, 6051030-X, 6052030-X , and
Quatro cables. Conductivity sensors are built into the 60530-X, 6051030-X, and
6052030-X cables and are not replaceable. Conductivity/temperature sensors
are shipped with the Quatro cable, must be installed, and are replaceable.
SEtUP - CoNDUCtIVItY
Press Sensor , highlight Setup, and press
enter. Highlight Conductivity, press enter.
Enabled allows you to enable or disable the
conductivity measurement. Highlight Enabled
and press enter to activate (
Q ) or deactivate ( P )
conductivity. Disable conductivity if you do
not have a conductivity sensor connected to the
instrument.
If a sensor is Enabled that isn’t connected to the instrument, the
display will show an unstable, false reading next to the units.
Temp Ref (Temperature Reference) is the reference temperature used for
calculating temperature compensated Specific Conductance. this will be the
temperature all Specific Conductance values are compensated to. the default
is 25 °C. to change the Reference temperature, highlight Temp Ref and press
enter. Use the numeric entry screen to enter a new value between 15.00 and
25.00 °C. Next, highlight <<<ENtER>>> at the bottom of the screen and press
enter on the keypad to confirm.
%/°C (Percent per Degree Celsius) is the temperature coefficient used to
calculate temperature compensated Specific Conductance. the default is
1.91% which is based on KCl standards. to change the temperature coefficient,
highlight %/°C and press enter. Use the numeric entry screen to enter a new
value between 0 and 4%. Next, highlight <<<ENtER>>> at the bottom of the
screen and press Enter on the keypad to confirm.
TDS Constant is a multiplier used to calculate an estimated tDS (total
Dissolved Solids) value from conductivity. the multiplier is used to convert
Specific Conductance in mS/cm to tDS in g/L. the default value is 0.65. this
multiplier is highly dependent on the nature of the ionic species present in the
water sample. to be assured of moderate accuracy for the conversion, you must
determine a multiplier for the water at your sampling site. Use the following
procedure to determine the multiplier for a specific sample:
Determine the specific conductance of a water sample from the site; 1.
Filter a portion of water from the site; 2.
Completely evaporate the water from a carefully measured volume of the 3.
filtered sample to yield a dry solid;
Accurately weigh the remaining solid; 4.
Divide the weight of the solid (in grams) by the volume of water used (in 5.
liters) to yield the tDS value in g/L for this site; Divide the tDS value in g/L
by the specific conductance of the water in mS/cm to yield the conversion
multiplier. Be certain to use the correct units.
If the nature of the ionic species at the site changes between
sampling studies, the TDS values will be in error. TDS cannot
be calculated accurately from specific conductance unless the
make-up of the chemical species in the water remains constant.
to change the multiplier, highlight TDS Constant and press enter. Use the
numeric entry screen to enter a new value between 0 and 0.99. Highlight
<<<ENtER>>> at the bottom of the screen and press Enter on the keypad to
confirm.
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