YSI Professional Plus - Manual (Page 17)

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Local DO allows for localized Do% measurements. this sets the calibration
value to 100% regardless of the altitude or barometric pressure. Highlight Local
DO and press enter to enable (
Q ) or disable ( P ) this function. Local Do is
a method for the Pro Plus to factor in the barometric pressure on each Do
measurement. In essence, if the barometric pressure changes you wouldn’t notice
the difference in the Do% readings in air-saturated water or water-saturated air.
Local Do is ideal for EU compliance. When Local Do is enabled, an L will
appear next to Do% on the run screen. Do mg/L readings are unaffected by the
selection of Do Local.
LDS (Last Digit Suppression) rounds the Do value to the nearest tenth; i.e.
8.27 mg/L becomes 8.3 mg/L. Highlight LDS and press enter to enable (
Q ) or
disable ( P ) this function.
DISPLAY - DISSoLVED oXYGEN
Press Sensor , highlight Display and press enter. Highlight DO and press
enter. All Do units can be displayed simultaneously. Highlight the unit(s)
and press enter to activate (
Q ) or deactivate ( P ) units from the run screen.
Note - You will not be able to display dissolved oxygen unless it is Enabled in the
Sensor Setup menu first, see previous section.
DO % will show Do readings in a percent scale
from 0 to 500%.
DO mg/L will show Do readings in milligrams
per liter (equivalent to ppm) on a scale from 0
to 50 mg/L.
DO ppm will show Do readings in parts per million (equivalent to mg/L) on a
scale from 0 to 50 ppm.
AUto StABLE - DISSoLVED oXYGEN
Auto Stable indicates when a reading is stable.When Auto Stable is enabled, AS
will blink next to the parameter until it is stable. once the parameter is stable,
AS will stop blinking.
to enable Auto Stable, press Sensor ,
highlight Auto Stable and press enter. Highlight
DO and press enter.
Highlight Enabled and/or Audio Enabled
(instrument will beep when the stability
is achieved) and press enter to confirm. the Auto Stable Sensitivity can be
decreased or increased. Highlight Sensitivity and use the left and right arrow
keys to slide the bar. the more sensitive you make it (larger black bar) the
harder it is to achieve stability in a changing environment.
the Auto Stable system works by examining the previous 5 readings, computing
the percent change in the data and comparing that change against a % threshold
value. the % threshold value is determined by the Sensitivity bar setting. the
following chart can be used as a guide when setting the Sensitivity bar.
Sensitivity selected by User % Data Variance Threshold
100 - Most Sensitive, Sensitivity
bar is set to the far right
0.05%
75 0.62525%
50 1.275%
25 1.8875%
0 - Least Sensitive, Sensitivity
bar is set to the far left
2.5%
Example:
the instrument obtained the following data:
Reading #1 95.5 Do%
Reading #2 95.7 Do%
Reading #3 95.8 Do%
Reading #4 96.1 Do%
Reading #5 95.3 Do%
the instrument is programmed to determine the minimum and maximum
data value over the previous 5 samples, and to compute the percent difference
between those values. In this example, that gives a percent change of:
% Change = 100 * ((96.1 – 95.3 ) / 95.3)
% Change = 0.83%
In this example, if the Sensitivity bar is set to the far right, the Auto Stable
requirement would not be met and AS would continue to blink. However,
if the sensitivity bar is set to the median threshold (1.275%), the Auto Stable
requirement would be met and AS would display steadily on the display.
Within the Auto Stable menu, you can also choose to Hold All Readings for as
many parameters as you set for Auto Stable. For instance, if Do and pH have