Specifications
A Remote Automated Water Quality Stream Gauging System Design 3
3
probes can be customised to measure up to 3000NTU. In the standard gauging system
design this probe is connected to a control port of the CR10x logger and assigned address 0.
The NEP180 series is used in installations where turbidity readings greater than 3000NTU
are expected. NEP180 probes provide an analogue (voltage) output that is measured using a
differential channel on the logger.
2.1.4. Velocity
Velocity is measured using a Unidata Starflow Ultrasonic Doppler Instrument. The Starflow
also communicates via SDI12. Standard measurements include water depth, velocity and
water temperature. The Starflow has an internal logger and is capable of computing flow rate
and discharge. It is possible to measure velocity in either direction along an axis parallel to
the long axis of the sensor. The sensor is connected to a control port on the data logger and
assigned address 1.
2.1.5. Rainfall
A Hydrological Services TB3 Tipping Bucket rain gauge is used for measuring rainfall at the
stream gauging sites. The unit consists of a 200 mm collector funnel with stainless steel leaf
filter and an integrated siphon control mechanism which can measure rainfall intensities up to
700 mm/hr. It includes dual output reed switches with varistor protection as well as dual
rainfall discharge outlets for water drainage. The bucket tips when precipitation of 0.2 mm
has been collected, activating a reed switch closure which is measured using the CR10x
logger pulse channel.
2.1.6. Auto sampler
Water quality samples are collected using an ISCO 3700 auto sampler. This device is
weather resistant, runs from 12VDC power and can collect 24 one-litre samples. It is
connected to a control port on the data logger which is used to trigger sample collection. The
unit is powered directly from a 12V battery. A length of 10mm ID Pirtek Ortac non conductive
sampling hose with a 2 mm screened aperture is connected between the unit and the in-
stream mounting point. The pump in the sampler alone is sufficient for hose lengths smaller
than 30 m with a pump heads below 5 m. At sites with high pump heads or hose lengths
beyond 30 m a secondary pump mounted in the channel is used.
When using a second pump, the sample line is purged to waste for a defined period. The
ISCO waits until that amount of time has passed and collects a sample from the line. The
pump is then switched off.
A Shurflo 9300
submersible pump is used to push water up to the ISCO sampler. This
diaphragm pump has corrosion proof housing and can operate with either 12VDC or 24VDC.
A 24V power system is used in this system to provide optimal pumping efficiency and to keep
the diameter of power cable to a minimum.
2.1.7. Power system
For standard gauging sites, the power system is comprised of a 20 W solar panel and a 120
A/Hr sealed wet type lead acid deep cycle battery. An automatic solar regulator charges and
maintains the battery.
Sites with a secondary pump have an additional solar panel, regulator and battery of the
same specifications. The two batteries are wired in series to create a 24VDC circuit.