Measurements are made using a YSI 6600 water quality sonde and YSI 6200 Data Collection Platform (DCP) with data radio telemetered to the PIE LTER Rowley field station.
YSI Sonde sensors consist of 6562 dissolved oxygen probe (rapid pulse – Clark type,polarographic), 6560 conductivity/temperature probe (thermistor) and vented level depth sensor (stainless steel strain gauge).
Missing data or blank values are caused by maintenance time periods or where sensor measurements are obviously wrong in the context of what would be expected.
For example, the conductivity sensor has a relatively small opening and chamber for the conductivity electrodes, the estuary can have varying suspended sediment/detrital loads moving in the water column which enter the conductivity cell shorting out the electrodes making a faulty conductivity measurement (lower than expected). Oxygen measurements are dependent upon the conductivity measurements so the oxygen also becomes erroneous.
Obvious measurements/data errors have been removed from the data set however the user of this data should also conduct their own data analysis to determine if the data are suitable for their particular situation.

Typical sensor/data problems are:
For oxygen: Fouling of Clark style DO probe where membrane gets a brownish bacterial? film affecting DO sensor readings/calibration checks.
For conductivity: Conductivity cell can have detrital material stuck in it, shorting out cell, resulting in lower than expected conductivity.
For depth: Depth strain gage pressure sensor may come out of the water at low tides resulting in many "zero" depth readings or sometimes negative values.