Campbell Scientific OBS-Mobile Software for Archer-OBS User Manual
Page 23
Section 2. Troubleshooting
Bright sun near the surface ( < 2 meters) or black-colored sediments cause
erroneous OBS readings.
Do not survey in shallow water between 10:00 and 14:00 local time and avoid
areas with suspended black mud.
Changing the water temperature in the setup dialog box does not change
the temperature measurement.
This is normal. Temperature inputs only change the water density correction
used to convert pressure to depth.
OBS-3A indicates different NTU values in the field than other
turbidimeters.
Not all turbidity meters read the same! OBS sensors are checked with a Hach
2100N laboratory instrument, using U.S. EPA-approved, formazin turbidity
standards before leaving our factory. Turbidimeters other than the 2100N will
read different NTU values on natural water samples.
OBS-3A indicates different suspended sediment levels in the field than in
the laboratory.
This results from a change in sediment size or color (see Section 8). You may
have to perform a field calibration with water samples.
2-3