OBS501 Smart Turbidity Meter with ClearSensor
®
Technology
33
Other than the sleeve and the biocide chamber on the
sensor tip, there are no user-serviceable parts inside
the sensor housing. Do not remove the sensor or
connector from the pressure housing. This will void the
warranty and could cause a leak.
Plastic (pn 31570) and copper (pn 31569) sleeves are available for the OBS501
to reduce required cleaning. The plastic sleeve is intended to be disposable. The
copper sleeve should slow fouling growth, but it may need to be cleaned. If the
sleeve becomes encrusted with organisms, such as barnacles or tube worms,
remove the sleeve. The sleeve can be soaked in weak acids or other cleaning
products that are compatible with copper. The sleeve may have to be gently
scraped with a flexible knife blade followed by a scouring pad such as
SkotchBrite
®
. For more information, see Appendix
(p. C-1)
.
Do not use solvents such as MEK, Toluene, Acetone, or
trichloroethylene on OBS sensors.
10. Troubleshooting
A common cause for erroneous, turbidity-sensor data is poor sensor
connections to the datalogger.
Problem:
Unit will not respond when attempting serial communications.
Suggestion:
Check the power (Red is +V and Black is Ground) and signal (White is SDI-12
Data) lines to ensure proper connection to the datalogger. Check the datalogger
program to ensure that the same port the SDI-12 data line is connected to is
specified in the measurement instruction.
The following three tests are used to diagnose malfunctions of an OBS501:
1.
The
Finger-Wave Test
is used to determine if an OBS sensor is ‘alive’.
Power the OBS sensor and connect datalogger (see Section
(p. 8)
). Wave your finger across the sensor window
about 20 mm away from it. The datalogger should show the output
fluctuating from a few TU to the full-scale signal. If there are no signal
fluctuations of this order, there is a problem that requires attention.
2.
The
Shake Test
is done to determine if water has leaked inside the
pressure housing. Unplug the cable and gently shake the sensor next to
your ear and listen for sloshing water. This test gives a false negative
result when the amount of water in the housing is large enough to destroy
the circuit but too small to be audible.
3.
A
Calibration Check
is done to verify if a working OBS sensor needs to
be recalibrated. In order to be meaningful, the user must have a criterion
for this test. For example, this criterion might be 5%. The sensor is placed
in calibration standards with the 1
st
and 2
nd
TU values listed in FIGURE
WARNING
WARNING
