Campbell Scientific OBS3 Turbidity Sensor - Manual (Page 5)

1
Interfacing the OBS-3 Turbidity Monitor
with Campbell Scientific Dataloggers
The OBS-3 Turbidity Monitor is a submersible probe manufactured and sold by D & A
Instrument Company. This application note provides a diagram of connecting the OBS-3
to a CR1000, CR10(X), CR23X, and CR510 datalogger and describes programming a
datalogger to read this probe.
The standard output for the OBS-3 is 0 to 5 V, which may be used with the CR23X and
CR1000. If response over 1000 FTU is needed for use with the CR10(X) or CR510
datalogger, order the probe with the optional 0 to 2500 mV output range.
When turbidity is very high, the OBS-3 probe can generate an
output greater than 5 V. To avoid the loss of data, ask D & A
Instruments to install a voltage limiting circuit in the probe that
clamps the output to 2.5 V or 5.0 V.
The OBS-3 probe may draw over 30 mA. Because this power
requirement is relatively high, we recommend you provide
switched power, such as the switched 12 V on the CR10X,
CR1000, and CR23X wiring panel. If power to the sensor is
continuous, you must use AC power or a solar panel with
excellent solar availability to maintain a good charge on the
battery.
1. Connections
Red
SW 12V
1H
1L
G
White
Green
Black
CR1000
FIGURE 1. Wiring Diagram of OBS-3 Using
Datalogger’s Switched 12 V
NOTE