YSI 52 - Manual (Page 13)

Calibration Section 3
5900 Series probes. This is the default zero value. Although using this average will result
in errors with probes whose background current differs from the average.
Note: Errors will be insignificant in most applications. See Discussion of Measurement
Errors.
For highest accuracy measurements, a zero calibration should be performed to
compensate for the specific background current of the probe in use.
To calibrate to a true zero, place the probe in a zero oxygen environment and adjust the
calibration value to zero.
A standard method for creating such an environment is to dissolve in water (preferably
the water should come from the sample to be measured) excess sodium sulfite (Na
2
SO
3
),
and a trace of cobalt chloride (CoCl
2
). These chemicals will remove all oxygen from the
sample (See Standard Methods for the Examination of Water & Wastewater, 17th
edition, 1989, page 4-161.) Alternatively, you may place the probe in 100% nitrogen gas.
Place the probe in the zero oxygen sample, switch to O
2
-TEMP and allow at least 20
minutes for the probe to come to equilibrium.
Switch to CALIBRATE. The display will show:
Press CONFIRM to select percent calibration. A display similar to the one below will be
shown:
C a l i b r a t e
i n p e r c e n t ?
E n t e r c a l v a l u e
L a s t = 9 2 . 5 %
Press SKIP twice to set the calibration value to 0.0%. The following display will be
shown.
E n t e r c a l v a l u e
Z e r o = 0. 0 %
Press CONFIRM to calibrate to zero. The display will ask you to wait, then show
"Calibrated to 0.0 %." After zeroing, rinse the probe thoroughly to remove any residual
trace of chemicals.
The Model 52 is calibrated at two points: the calibration value you select, and its default
zero.
YSI, Incorporated Model 52 9