A Versatile UV Nitrate Sensor for Operation in Diverse Environments
- Reduced 5mm pathlength for high turbidity environments
- Active fouling control with fully integrated Hydro-Wiper
- Internal data logging and scheduling with 2 GB memory
- Full Freshwater & seawater calibrations
- USB communications and data download
- SDI-12 interface
|Limit of Detection|
0.5 μM (FW or SW with T/S correction)
2.0 μM (SW 0-40 psu)
3000 μM (10 mm path length)
4000 μM (5 mm path length)
± 2 μM (± 0.028 mg/I-N) or ± 10% of reading
|Short-term precision (at 3σ)|
0.3& μM (FW or SW with T/S correction)
2.4 μM (SW 0-40 psu)
|Drift (per hour lamp time)|
0.3 µM (FW or SW with T/S correction)
1.0 µM (SW 0-40 psu)
625 NTU* (10 mm path length; absent other absorbing species)
1250 NTU (5 mm path length; absent other absorbing species)
*Nephelometric Turbidity Units
|Path Length||10 mm & 5 mm (high turbidity option)|
|Wavelength Range||190-370 nm|
|Lamp Type||Continuous Wave, Deuterium Lamp|
|Lamp Lifetime||900 h|
|Input Voltage||8-18 VDC & 8-15 with Hydro-Wiper|
|Power Consumption||7.5 W (0.625 A at 12 V) nominal|
100 m with Hydro-Wiper
3.1 kg with Hydro-Wiper
2092 cm3 with Hydro-Wiper
Real-Time temperature-salinity correction available* (0-35o C, 0-40 PSU)
* Requires external T/S data.
The Satlantic SUNA Nitrate sensor is complemented by SUNACom, a graphical software application available for Windows and Mac that makes SUNA set up, SUNA operation and in-field calibration updates easy and robust.
SUNACom software makes it easy to:
- Configure any SUNA setting and control SUNA operating mode.
- Update SUNA calibration with step-by-step calibration wizard, including PDF calibration reports, calibration file comparison utility, and calibration file upload.
- Graphically plot processed and/or raw SUNA data in real time or via file playback. View nitrate and ancillary time series and navigate sequenced absorbance plots and UV spectra.
- Re-process previously logged SUNA data files. Experiment with different processing parameters and calibration files to re-calculate nitrate values.
- Define custom meta-data fields to better organize logged SUNA data.
- Convert raw or processed SUNA data to calibrated comma separated values suitable for import to spreadsheets and database.
Please see the release notes for a complete list of features and improvements and refer to the SUNA User Manual for more information.
Download SUNACom 3.0.4
Is an instrument with the class based calibration still within the published specification for accuracy? If not, what is the accuracy?
Instrument specific calibrations are more accurate and correspond to the published accuracy specifications.
The accuracy of the class based calibration is estimated to be 2.2 uM +/- 20%.
Why is the diameter larger?
The diameter is larger because the pressure case wall thickness was increased to improve the robustness of the instrument for more rugged deployments. As a result, the depth rating also increased to be 500 m from the previous 100 m.
What is "adaptive sampling" and how does it work?
The SUNA V2 contains a 256 channel spectrometer that is programmed to integrate for a specific length of time (usually 300 - 500 ms) while sampling to maximize signal. That is, when the SUNA V2 takes a sample, the spectrograph collects UV light for the length of the integration period. In optically dense waters (e.g. high turbidity or CDOM), very little UV light is transmitted through the water and therefore the spectrometer "sees" a much lower signal. The new SUNA V2 is programmed to automatically increase the integration period to compensate for the low light levels. This enables the instrument to collect a strong signal in extreme environmental conditions.
How does absorption from CDOM affect the SUNA V2 nitrate measurement?
The SUNA V2 determines nitrate concentrations from the shape of the UV absorption curve. The least squares curve fitting algorithm uses calibrated extinction coefficients for nitrate and bromide (strong absorbing species in salt water) to calculate the concentration of nitrate from the UV absorption curve. The algorithm also employs a linear baseline correction that accounts for absorption that is not associated with either nitrate or bromide. The linear baseline correction successfully compensates for CDOM absorption in cases where the CDOM absorption is close to linear in the low UV. The composition of CDOM is dependent on the type of drainage area around a particular watershed and is therefore highly variable. As a result, the shape of CDOM absorption curve can vary from region to region. For this reason, the baseline correction does not always successfully compensate for CDOM absorption. In cases where the CDOM absorption curve mimics the shape of the nitrate absorption curve, a positive bias can occur.
The most common approach for correcting a positive bias caused by CDOM absorption is to correlate the continuous in situ nitrate data provided by the SUNA V2 with nitrate concentrations from discrete water quality samples measured in a laboratory. The bias may then be calculated either as an absolute offset or as a factor. In order to provide the most robust correction possible, the discrete sample size should be sufficiently large to allow for comparisons and the relationship between the in situ and discrete concentrations should be highly correlated.
How do I tell if my SUNA is a V1 or V2?
You can identify which model of SUNA you have by the firmware revision it is running. The firmware information can be viewed by either starting the SUNA in a terminal emulator (information is in the start-up banner), or connecting the instrument to SUNACom (information is in top left corner, next to serial number). The first digit of the firmware revision identifies the version of the sensor, ie. firmware v1.9.0 indicates a SUNA V1.
When running my SUNA V2 on the bench, the data shows that the lamp is turning on and off. Why is this happening?
This is a safety feature of the instrument, whereby the lamp is turned off when its temperature reaches 35°C (95°F) to prevent damage from overheating. The SUNA continues to output dark frames while monitoring the temperature, and will restart the lamp once it has dropped back below 35°C. If extended in-lab use is required, immersing the SUNA in a cool bath can prevent this behavior.
How does the free calibration differ from the fresh water calibration?
The included class-based calibration coefficients are average coefficients obtained from our library of historical calibrations. The historical coefficients that are averaged to create the class based coefficients vary by about 10%.
- Pellerin, B.A., Bergamaschi, B.A., Downing, B.D., Saraceno, J.F., Garrett, J.A., and Olsen, L.D. (2013) Optical Techniques for the Determination of Nitrate in Environmental Waters: Guidelines for Instrument Selection, Operation, Deployment, Maintenance, Quality Assurance, and Data Reporting U.S. Geological Survey Techniques and Methods 1–D5, 37 p Read Now
- Pellerin, B.A, Saraceno, J, Shanley, J.B., Sebestyen, S.D., Aiken, G.R., Wollheim, W.M., Bergamaschi, B.A. (2011) Taking the pulse of snowmelt: in situ sensors reveal seasonal, event and diurnal patterns of nitrate and dissolved organic matter variability in an upland forest stream. Biogeochemistry doi:10.1007/s10533-011-9589-8 Read Now
- Sackmann, B.S. (2011) Deschutes River Continuous Nitrate Monitoring. Quality Assurance Project Plan: Deschutes River Continuous Nitrate Monitoring, PUblication Number: 11-03-030 Read Now
- Heffernan, J.B., Cohen, M.J. (2010) Direct and indirect coupling of primary production and diel nitrate dynamics in a subtropical spring-fed river. Limnol. Oceanogr., 55(2), 677 - 688.
- MacIntyre, G., Plache. B, M.R. Lewis., Andrea, J, Feener, S, McLean, S.D. (2009) ISUS/SUNA Nitrate Measurements in Networked Ocean Observing Systems. White Paper Read Now
- Prestigiacomo, A.R. (2009) Nitrate and Bisulfide: Monitoring and Patterns in Onondaga Lake, New York, Following Implementation of Nitrification Treatment, Prestigiacom, A.R, Effler, S.W., Matthew, D.A., Coletti, L.J., Water Environment Research, 81(5)
- Johnson, K.S., Coletti. L.J. (2002) In situ ultraviolet spectrophotometry for high resolution and long-term monitoring of nitrate, bromide and bisulfide in the ocean. Deep Sea Research 49 1291-1305
The Hydro-Wiper is an external anti-fouling system fully integrated with the SUNA V2. The Hydro-Wiper keeps the SUNA V2 sample windows clean for several months even in the most aggressive fouling environments, helping prevent costly site visits for manual cleaning and loss of data.
SUNA V2 Anti-fouling guard
The SUNA V2 anti-fouling guard is a semi-circular piece of perforated copper attached to a plastic armature that fits into the sample chamber. The anti-fouling guard provides passive fouling prevention through the release of copper ions that inhibit biological growth in the area. The anti-fouling guard provides a reliable and affordable approach to increase deployment time, decrease operating costs, and collect high quality data for mooring applications.
SUNA V2 Flow cell
The SUNA V2 flow cell is designed to adapt the SUNA V2 for flow through operations on moorings with pumped flow, ship-board underway systems or for laboratory testing and calibration. The flow cell attaches to the SUNA V2 sample chamber and tightly seals against the optical chamber windows. Nylon barbed fittings are provided to connected the flow cell to available pumped flow.
SBE 5P Pump
The pump module is a compact unit consisting of a centrifugal pump head and a long-life, brushless, DC, ball-bearing motor. The pump impeller and electric drive motor are coupled magnetically through the housing, providing high reliability by eliminating moving seals. The 5P has a 600-meter (1960 ft.) plastic housing.
Satlantic's reliable and user-friendly Alkaline Battery Packs are available in 102 Ah and 51 Ah capacities. The design of the internal battery compartment allows the user to easily change the D-Cell batteries with off-the-shelf replacements. The battery packs consist of an anodized aluminum pressure case, a D-cell battery compartment and a removable end-cap.