YSI 9600 - Manual (Page 34)

SECTION 4 STARTING A 9600 DEPLOYMENT
4.1 UNDERSTANDING CALIBRATION OF THE 9600
As described above, part of the reagent package of the 9600 is a standard (usually 1mg/L or higher
concentration for a 9600-02 and 1 mg/L or lower for a 9600-10) and a blank (purified water with no nitrate
present). These reagents are run through the system periodically during a deployment providing on-board
calibration that compensates for any instrument drift. These calibration points are used to convert the
optical readings from actual samples into nitrate values in mg/L of nitrate-N. This calibration protocol is
transparent to the user.
When starting a 9600 deployment, users will have to make three choices that will affect the calibration of
the instrument during the study. These choices are input to the 9600 software in the deployment “Wizard”
which is described in Section 4.4 below.
1. The first choice is the frequency of calibration, i.e., how often the standard and blank are run during a
deployment. YSI generally recommends that calibration be carried out every 12 hours and no less
often than once every 24 hours. The number that you will enter is the number of samples between
calibration points. Thus, if you want to calibrate every 12 hours and your sample interval is 1 hour,
you would enter 12. However, if your sample interval were 30 minutes (0.5 hours) you would enter
24 to obtain a calibration every 12 hours.
2. The second choice is the concentration value for the nitrate standard in units of mg/L of nitrate-N.
YSI recommends the use of a standard with a concentration of 1 mg/L for your first deployment at a
given site. If it turns out that the nitrate levels at this location are consistently lower or higher than this
value, then you can choose standards of other concentrations for subsequent studies.
3. The final choice is your sample interval that does in fact have an indirect effect on the timing of the
calibration. A standard calibration protocol (blank and standard analyzed by the 9600 flow system)
takes slightly less than 15 minutes to complete. This means that it is not possible to run the calibration
routine between samples at the lowest allowed sample interval of 15 minutes. If a 15 minute sample
interval is selected, the calibration sequence will thus displace one data point, slightly interrupting the
continuous data stream. For sample intervals over 15 minutes, the calibration will automatically occur
between samples and a continuous data stream will be logged at the user-selected interval.
NOTE CAREFULLY: When using your 9600 with a data collection platform (DCP) via an SDI-12
interface, the MINIMUM SAMPLE INTERVAL ALLOWED IS 30 MINUTES. See Section 5.5
below for details on the setting up of your instrument for DCP interface.
More information on these selections is found in Section 4.4 below.
4.2 CHECK LIST FOR DEPLOYMENT READINESS
After interfacing to the 9600 with NUview software as described above, the following display will be
shown.
YSI Environmental 34 Model 9600 Nitrate Monitor