OBS-3A Turbidity and Temperature Monitoring System
FIGURE 4-1. Anatomy of an OBS sensor
4.2 Temperature and Optional Sensors
Temperature is measured with a fast-response, stainless steel-clad thermistor.
Pressure is measured with a semiconductor piezoresistive strain gage.
Conductivity is measured with a four-electrode conduction-type cell. Working
depths for available pressure sensors are listed in TABLE 6-1.
4.3 Optics and Turbidity Measurements
Turbidity is the cloudy appearance of a liquid produced by light scattered from
suspended matter. It is an
apparent
optical property that depends on the size,
color, and shape of scattering particles, and the instrument used to measure it.
In accordance with standard method 2130B and ISO 7027, turbidity is usually
measured with a 90°-scatterance nephelometer and reported in NTUs.
Turbidity standards are discussed in Section 7,
Calibration
.
FIGURE 4-2. Optical particle detectors
3
