RBRduo³ and RBRconcerto³: C.T, C.T.D, C.T.D++

RBRduo³ C.T and RBRconcerto³ C.T.D
The RBRduo³ C.T and RBRconcerto³ C.T.D are built on the years of experience RBR has creating reliable and easy-to-use instruments. They are uniquely designed to determine salinity by measuring the conductivity and temperature of water. Equipped with a pressure channel, the RBRconcerto³ C.T.D can also derive depth, density anomaly, and speed of sound. These self-contained, accurate, and autonomous submersible instruments can be deployed for a period of up to five years at 1min sampling intervals, and the data is retained in memory even after the batteries are removed.

Salinity
Conductivity measurements are performed using a rugged inductive cell suitable for deployment in marine, estuarine, or fresh water. There are no exposed contacts, which avoids susceptibility to corrosion, and the housing may be frozen into ice without damage. It is characterized for the mechanical effects of both temperature and pressure to allow for accurate correction in salinity derivation. These coefficients are provided for customers who prefer to calculate their own corrections. In addition, it is suitable for use outside the usual realms of PSS-78 practical salinity scale, in applications such as desalination brine monitoring. The conductivity readings are temperature-corrected.

For profiling applications, the co-located thermistor reduces salinity spiking, thus increasing data accuracy. 

Equipped with a piezoresistive pressure channel, the CTD instruments provide more accurate salinity data when the instrument is sampling at varying depths.  

Additional sensors
A diversity of sensor configurations allows the instrument to be fine-tuned for a wide variety of applications. Variants with pressure, temperature, conductivity, radiometer, PAR, and turbidity sensors are also available in titanium housing, designed to endure harsh conditions.

Physical Storage 240M readings Power1 8 AA cells External power 4.5 to 30V Communication USB-C or RS-232/485 Clock drift ±60 seconds/year Housing Plastic or titanium Diameter 63.3mm (plastic), 60.3mm (Ti) Length Configuration dependent Weight Configuration dependent Depth rating2 Up to 6000m (configuration dependent) Sampling rate 2Hz; options up to 32Hz 1 Lithium thionyl chloride batteries are only recommended for the RBRduo³ C.T and RBRconcerto³ C.T.D. Use alkaline or lithium iron batteries for all other configurations. 2 The depth rating for RBRconcerto³ Tx may be up to 8000m.

Conductivity Range 0-85mS/cm Initial accuracy ±0.003mS/cm Typical stability 0.010mS/cm/year Resolution 0.001mS/cm

Temperature Range3 -5°C to 35°C Initial accuracy ±0.002°C Resolution <0.00005°C Time constant <0.1s | fast, <1s standard Typical stability 0.002°C/year 3A wider temperature range is available upon request. Contact RBR for more information.

Pressure (Depth) Range4 20 / 50 / 100 / 200 / 500 / 750dbar (plastic) /1000 / 2000 / 4000 / 6000dbar (Ti) Initial accuracy ±0.05% full scale Resolution <0.001% full scale Time constant <0.01s Typical stability ±0.05% full scale per year 4Recommended depth for wave measurements is less than 50m.

Turbidity (Seapoint®) Light source 880nm Time Constant 0.1s Linearity <2% deviation for 0-1250 FTU

Fluorescence (Seapoint®) Excitation 470nm / 685nm (chlorophyll a) 370nm / 440nm (cDOM) Time Constant 0.1s

Dissolved Oxygen Sensor (Oxyguard®) Range 0 to 600% Initial accuracy ±2% O2 saturation Resolution 1% of saturation Response Time ~10s, 90% step change at 20°C Contact RBR for other sensor options.