Xylem 6-Series Multiparameter - Manual (Page 81)

Sondes Section 2
YSI Incorporated Environmental Monitoring Systems Operations Manual 2-75
2.9.2 CALIBRATE
All of the sonde sensors (except temperature) require periodic calibration to assure high performance.
However, the calibration protocols for Rapid Pulse Polarographic dissolved oxygen are significantly
different depending on whether the sonde is being set up for spot sampling or longer term unattended
monitoring studies. This difference is user-selectable and is required primarily because the optimal
performance of the Rapid Pulse dissolved oxygen sensor cannot be attained unless the control of this sensor
varies from short term to long term applications.
For spot sampling it is best to pulse the sensor continuously during the Run mode to attain the most
accurate results and optimize the response time. However, this continuous pulsing is not ideal for longer
term logging studies in which the sonde data is captured to sonde memory or to a data collection platform
at much less frequent intervals (e.g. 15 minutes). Continuous pulsing not only shortens the time between
required probe maintenance, but consumes more power. With proper selection of the “Auto sleep” option
(discussed in detail in Section 2.9.8, Advanced Menu), the user can configure the sonde software to either
run continuously or “go to sleep” between samples to minimize Rapid Pulse DO probe wear and conserve
power. The effect of this choice on the user interface relative to dissolved oxygen calibration is significant
as described below:

If “Auto sleep” is deactivated, the sonde runs continuously no matter what sample interval has been
selected. Under these conditions, the user retains manual control of the dissolved oxygen calibration
routine, viewing the stabilization of the readings in real time and confirming the calibration with
keyboard entries.

If “Auto sleep” is activated, the sonde will „warm up‟ the sensors for the period of time selected for
the DO sensor. Under these conditions, the user loses manual control of the Rapid Pulse DO
calibration routine. Rapid Pulse DO will automatically calibrate after the selected time for warm up of
the DO sensor has expired. In this mode of calibration, you do not observe stabilization of the readings
in real time, but instead will observe a countdown of the warm up period followed by a message
indicating that the Rapid Pulse DO calibration is complete.
Only the calibration of Rapid Pulse dissolved oxygen is affected by whether “Autosleep” is on or off; the
user retains manual control of the calibration of all other parameters regardless of the “Auto sleep” setting.
Once a particular warm up time (in seconds) has been utilized in Rapid Pulse DO calibration, the length of
that time should not be changed during a study. A new calibration should be performed whenever the value
of the warm up time is altered.
Note that the ROX Optical DO sensor is not subject to the above issues relative to the activation of
“Autosleep RS232” for the Rapid Pulse DO sensor. The ROX sensor calibrates in the same way as any
other sensor such as conductivity, pH, or turbidity where the user manually confirms the calibration after
the sensor readings have shown stability.
From the Main sonde menu select 2-Calibrate. The Calibrate menu will be displayed. Only the enabled
parameters will be available for calibration.