YSI ProDSS Meter Calibration and Maintenance
K:\Streamkeepers\Monitoring\Eqpt & supplies\Calibration-Maintenance\SOPs\YSI ProDSS maint-
cal SOP's
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21. If the end point was overrun, back-titrate the sample with the bi-iodate standard (1 drop =
0.05 mg/L using a disposable 2 mL pipette) and correct the final value and data sheet. (For
values halfway between the 0.1 mL marks, round down even numbers and round up odd
numbers.)
22. Sodium Thiosulfate Normality Check: When the sample has been titrated to its end point, add
10 mL of the bi-iodate standard to the sample using the pipette in the cardboard box. This is
the “nominal value” that you’ll record on the data sheet. Then record the correction factor for
that pipette (i.e., how many actual mL are delivered for 10 mL nominal value on the pipette,
as measured by repeated tests with purified water, an accurate balance, and factoring in air
temperature). Refill the burette with sodium thiosulfate and re-titrate. Record the volume of
the “sodium thiosulfate normality check” volume needed to back-titrate to clear.
23. Titrate the other two samples following the same steps as the first. Make sure you refill the
burette and dab any excess fluid from the burette tip between each sample.
24. Wash the glassware and put away all liquids and equipment. Check the dates and amounts of
all solutions used to ensure there’s enough unexpired liquids for the next calibration activity.
If not, inform the office staff immediately.
Meter Samples
1.
Place the bucket of prepared DI water in the sink
2.
Record the time and take water temp, DO, and conductivity readings from the meter in the
bucket as follows:
3.
Place the probe in the bucket of DI water and allow the temperature to stabilize
4.
Wait for the readings to stabilize: DO sat ± .5% & Temp ± 0.1˚ for 30 sec. then press ENTER
to store the readings
5.
Remove probe
6.
On the unit, select the
file button
, select View Data, then select Show Data. Scroll to
the right to see the parameter values, record this on the data sheet
7.
Repeat for a second trail if necessary
8.
After all trials are done, rinse probe with DI water, shake off the probe and place back into
the calibration cup.
Post Winkler Calibration Check
1.
Record time on data sheet under “Post-sampling cal-
”.
2.
Rinse the calibration cup with clean tap water, fill the cup with 1/8
th
inches of clean tap water
3.
Place unit into calibration cup, slightly tighten the calibration cup onto the bulkhead but do not fully
tighten, allow for atmospheric venting.
4.
Set the unit upright for 5-15 minutes
5.
Allow meters to stabilize: for 2 minutes, both DO% and Temp. (
°
C) remain within
±
0.1 of their
initial readings. Record the time, temp, and post-cal DO%.
6.
Save or record readings at this time
7.
You can now pack everything up and record your sampling data from the meters back at the lab.
