Specifications

A Remote Automated Water Quality Stream Gauging System Design 2
2
2. SYSTEM OVERVIEW
The three principal elements that comprise the standard stream gauging station are the
electronics, infrastructure and the data-server.
The electronic components are the measurement, control and communication devices
located at the site of monitoring. Sensors and sampling hoses are installed in the stream
channel. The system control and communication components are located on the stream
bank above the high water mark.
The infrastructure components provide protection and fixed mounting points for electronic
components. A platform provides the basic structure which houses the components on the
stream bank. A pier oriented mounting system is used for fixing the sensors in the stream
channel.
The data-server is located in a laboratory and is used to download and process data from the
remote sites.
2.1. Electronic components
2.1.1. Data logger
All systems are controlled using a CR10X data logger manufactured by Campbell Scientific.
The logger uses 12VDC power, is fully programmable and has a number of analogue and
digital I/O ports for measurement and control. Communications with the CR10x are possible
through a DB9 serial I/O interface either by direct cable connection or via telemetry using a
modem and interface.
The loggers are supplied with support software that can be used for custom programming,
real time viewing of station data and scheduled data collection through telemetry.
Programming methodology is discussed later in section 4.
2.1.2. Depth
A Greenspan Analytical PS7000 pressure transducer is mounted in-channel to measure
water depth which is used to determine when a flow event is occurring. The pressure
transducer is cased in stainless steel and is equipped with a 4-20 mA electrical output as
standard. The output is measured using a differential channel on the CR10x. A cable length
of 10 m is supplied as standard, although lengths of up to 100 m have been used for some
installations. A closed venting system, incorporating a vent bag with inbuilt desiccant,
compensates for changes in atmospheric pressure and prevents water ingress into the
transducer through condensation.
Standard ranges for this transducer are between 0 m to 2.5 m and 0 m to 100 m with a
reported accuracy of 0.1 % full scale range. The PS7000 can be re-ranged in the field using
an optional cable harness and software that allows direct connection via RS232.
2.1.3. Turbidity
Turbidity is measured using an Analite NEP390 or NEP180 series sensor from McVan
Instruments, depending on the level of turbidity required to be measured. Both sensors are
housed in stainless steel, have a small form factor and operate using 12VDC power.
The NEP390 series offers an SDI-12 digital interface which allows multiple addressed probes
to be measured using a single logger port. The 390 series is available with a detachable
cabling connector and an automatic wiper which can be used if bio-fouling is expected. The