Monitoring Turbidity (Ntu); Water Density And Barometric Corrections; Sample Statistics - Campbell OBS-5+ Operator's Manual

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2) Wave your hand in front of the OBS-5+ sensor; the turbidity and SSC

3) Blow into the pressure sensor or press your thumb on it to compress air on

4) Click

6.2.6 Monitoring Turbidity (NTU)

The OBS-5+ was calibrated and factory-certified using AMCO Clear, U.S.

EPA-approved turbidity standards (www.gfschemicals.com). In order to

measure turbidity, the electronic gain of the near detector is set to the

calibration value and the active lookup table is overridden. Consequently, the

unit cannot simultaneously measure SSC (g L

NTU is selected. You must choose one or the other.

Instrument depth is estimated from pressure and it is important to set the water

temperature and salinity so the OBS-5+ can correct for water density and

calculate depth correctly. The sensor measures absolute pressure so the

instrument must also correct for barometric pressure. Be sure to do this while

the OBS-5+ is at the surface. Depending on the magnitude of barometric

pressure fluctuations at the site and the desired accuracy, you may want to

correct data for atmospheric effects using barometric pressure simultaneously

recorded at a nearby site.

The individual measurements are not recorded in the data flash memory and

you must select the sample statistics that will be recorded. Two types of

statistics can be selected for OBS-5+ measurements.

levels on the top plot will fluctuate as data scrolls across the plot.

the diaphragm (FIGURE 4-1). A small elevation in the pressure signal

will occur (bottom plot).

Stop and then

depth corrections, and software versions.

OBS-5+ System

OBS Settings to view time, serial numbers,

–1

) and NTU when either g L

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