YSI Pro20 - Manual (Page 26)

T A K I N G M E A S U R E M E N T S
Before taking measurements, be sure the instrument has been calibrated to ensure
the most accurate readings. Turn the instrument on and wait 5-15 minutes if
using a polarographic sensor. If using a field cable/sensor, install the sensor guard
to protect the sensor and membrane. Place the probe in the sample to be
measured and give the probe a quick shake to release any air bubbles. Allow the
temperature readings to stabilize. Next, stir the probe in the sample to overcome
the stirring dependence of the dissolved oxygen sensor. You must provide at least
6 inches (16 cm) per second of water movement. Once the values plateau and
stabilize you may record the measurement and/or store the data set. The dissolved
oxygen reading will drop over time if stirring is ceased. If placing the DO sensor
into a stream or fast flowing waters it is best to place it perpendicular to the flow
and NOT facing into the flow.
If using the DO sensor in an aeration tank/basin it is helpful to make sure bubbles
do not burst on the membrane. This may cause unstable readings to occur. You
should be able to prevent this by pointing the sensor upwards so it’s facing the sky
and twist tying, zip tying, or rubber banding the bulkhead to the cable. Essentially
making a simple curve to the cable without bending or breaking the cable will
allow you to lower the sensor into the aeration tank while the sensor points
skyward and the bubbles are no longer bursting on the membrane surface.
S A V I N G A N D V I E W I N G D A T A
The Pro20 can store 50 data sets in non-volatile memory for later viewing. A data
set includes the values currently on the display, i.e. temperature in Celsius or
Fahrenheit and dissolved oxygen in % and/or mg/L or ppm. Each data point is
referenced with a data set number, 01 through 50.
The Pro20 can not communicate to a PC via a Pro Plus
communications saddle. Connecting the Pro20 to a
communication saddle may cause erratic instrument behavior.
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SAVING DATA
From the run screen, use the up or down arrow keys to highlight the Save box and
press enter to save the current readings. The instrument will indicate the data set
is saved and display the saved data set’s number (Figure 11).
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