Vernier Tech Info Library TIL #372

Question

Suggestions for using the Dissolved Oxygen Probe.

Answer

We receive very few Dissolved Oxygen Probes back for repair. The probes are rather robust, and if used properly very accurate.

Most people who experience difficulty with DO Probes do so because they do not have the proper calibration procedures to follow. The procedure for calibration can be found in the DO Probe booklet that came with the sensor or one of our lab manuals such as �Water Quality with Computers� or �Water Quality with Calculators�. If you do not have access to those manuals, you can download the Dissolved Oxygen chapter from the manuals on our website at:

http://www.vernier.com/cmat/wqc.html (for �Water Quality with Computers�)
http://www.vernier.com/cmat/wqcalc.html (for �Water Quality with Calculators�)

If the calibration procedure is followed carefully, the readings from the Dissolved Oxygen Probe are as accurate, and more precise, than a DO titration test.

Below are some general tips to follow when working with the Dissolved Oxygen Probe:

A) Do you really need to calibrate? For most Biology with Computers experiments, or beginning water quality measurements, simply warming up the probe, and using the STORED calibration works just fine. For the most accurate readings possible, calibration is suggested.

B) If calculators are being used, make sure that you use the CHEMBIO, DataMate, or EasyData calculator programs.

C) The DO Probe can be left soaking in water with the filling solution still in the electrode for several days. For long-term storage, however, the filling solution should be removed and the probe stored dry.

D) If you have carefully calibrated the Dissolved Oxygen Probe and you still fail to get good readings, check the integrity of the membrane cap. Inspect the cap for holes or tears in the membrane. Also, check to make sure that the membrane has not become clogged with dirt and oil. If you hold it up to a light, you should be able to see if it is dirty. If you are not sure, switch out the caps and see if that fixes the problem.

E) If you have tried everything and your DO Probe is still not behaving properly, please call Vernier Technical Support at 888-837-6437 or info@vernier.com

Created by: dholmquist on August 05 1998
Last updated by: mcollins on May 01 2006