Xylem 6-Series Multiparameter - Manual (Page 84)

Sondes Section 2
YSI Incorporated Environmental Monitoring Systems Operations Manual 2-78
membrane installed on the 6150 probe and NOT a function of the probe, i.e., the constants reflect the
characteristics of the sensor membrane and NOT the probe. When a 6150 probe is purchased from YSI, it
already has a sensor membrane installed and the constants of that membrane are transferred automatically
to the sonde PCB when the sensor is run for the first time. After transfer, the constants can be viewed by
accessing the Advanced|Cal Constants menu as shown below – the regression constants are ODO K2-
ODO K4 and the value at zero oxygen is K1 as shown below.
It should also be noted that the ROX sensor is characterized by two additional parameters – ODO Gain and
Tzero. The ODO gain reflects the small change in the calibration which is carried out be the user in a 1-
point calibration as described below. The Tzero value will always be the same as K1 until the user elects
to perform a 2-point calibration as described below at which time it will change slightly to reflect the
adjustment of the zero oxygen value.
You will also note that a different set of constants for your specific sensor membrane are supplied on the
instruction sheet which came with your 6150 probe. These five constants (K1-K4 and C) have a different
appearance than those shown in Advanced|Cal Constants because they are in coded form to allow error-
free reentry by the user in the unlikely event that the regression constants in the probe are lost. The C
constant is a check sum value associated with the values of K1-K4 and will prevent acceptance of the
constants if typographical errors are made in their entry by the user. The coded constants must be entered
in the Calibrate|Optic X – Dissolved Oxy|Enter Cal Sheet as shown below. The constants can also be
viewed at any time by selecting Calibrate|Optic X – Dissolved Oxy|View Cal Sheet.
YSI recommends that your replace your sensor membrane after 1 year of use by purchasing the 6155
Optical DO Membrane Replacement Kit. This kit will be supplied with a new set of coded constants