Note: If the probe is being air calibrated in a pipe where the end of the pipe is
submerged,
vent holes must be drilled on both ends of the pipe to allow ambient
air to purge the gases, which might give a false air calibration value. Drill holes in
pipe just above the water line and at the top of the pipe. When air calibrating, the
probe should be suspended between the holes in a white PVC pipe to help reflect
heat from the sun.
Do not air calibrate the FL-2 if air temperatures is + 10 or -10 degrees from water
temperature. Leave the probe in the water and use a handheld to compare readings. The
FL-2 has temperature compensation, so never calibrate it until you know the probe has
had ample time to adjust to temperature. If the readings do not look right to you
investigate everything involved and wait till the next day to try again.
Suggested calibration for wastewater treatment:
There are four (4) basic ways to
calibrate the Fluoroprobe
TM
controller, which are described in the following sections.
If you are using the FL-2 in a wastewater application and your operation range is 3 or 4
ppm down to 0 ppm use a hand held instrument to compare or calibrate. The sensor is
more responsive and stable when left continuously in the water and calibrated within its
normal operating environment. Always clean sensor with a toothbrush and place back in
aeration 30 minutes or longer before any calibration. Bio-growth or debris covering the
sensor will cause oxygen reading to slowly fall to zero, the only maintenance needed is
once a month toothbrushing. Many aeration basins never have this growth problem.
1. Air Saturated Water Calibration:
. For this technique, a volume of water must be
aerated for twenty (20) minutes or longer at a constant temperature. The operator can
use an aquarium pump and a stone diffuser (air stone). A cylinder of some type is best.
PVC pipe (2"or 3") with a cap on the bottom is a good vessel to use for this method.
Place the probe in the aerated water keeping the probe sensor near the top of the
container for maximum efficiency. To obtain the correct current atmospheric pressure
reading, use the local altitude or the true atmospheric pressure from a mercury
barometer or weather bureau report. The same air calibration table used for
polargraphic or galvanic calibration may also be used for reference. This technology is
for long term monitoring and taking your time is very important when calibrating this
instrument. After the probe has been submerged for twenty (20) minutes or more in the
air-saturated water, press the
READ
button on the faceplate of the instrument. The
operator will have about two (2) minutes to adjust the air calibrate adjustment screw on
the faceplate to the air saturated water concentration. No water flow or movement in
the probe is necessary in order to obtain 0
2
concentration readings. A hand held
oxygen meter can be used in calibration to assure air saturation. If you are also zero
calibrating, be sure to clean the probe before changing from one liquid to the next.
