Dissolved Oxygen Pen by SPER Scientific (Mark Rothenay)

Author

Mark Rothenay - Bert Corona Charter High School

Sensor / Probe

Features:

• Heavy duty polarographic D.O. probe including temperature sensor

• Automatic Temperature Compensation

• Microprocessor assures high accuracy

• IP-67 water resistance

• Data hold

• Dual display LCD

• Auto power off

Measurement Procedures for Dissolved Oxygen (DO) Measurement

1. Make certain the meter has been calibrated.

2. Press and hold the UNIT button for at least 2 seconds, the display will change from %02 to mg/L.

3. The meter is now ready to measure.

4. To activate Automatic Temperature Compensation the probe head must be immersed to a depth of 3cm. It takes several minutes for the temperature of the probe and liquid to equalize.

5. For accurate DO measurement of any liquid, the probe should be moving. make sure that the velocity of the movement is at least 0.2-0.3m/s. This can be achieved by shaking the probe.

Sample Investigation

Background on why I chose this probe

Some of my students and myself are conducted a longitudinal study concerning the California Toad (Anaxyrus boreas halophilus) in the southwestern San Gabriel Mountains. My students are researching how the amount of rainfall affects the population of this species in this particular area. We have identified several sites where the toads mate and lay eggs but noticed in temporal pools the tadpoles morph into toadlets at a faster rate when compared to small moving streams.

The water in these temporary pools was warmer when compared to these streams and some students theorized that since the increase in temperature along with decaying organic matter, this decreases the amount of available dissolved oxygen and thus might serve as an environmental factor in speeding up the metamorphic mechanisms. This serves as

Sample Investigation

How does the increase in temperature of freshwater affect the amount of dissolved oxygen present?

1. Measure the dissolved oxygen (D.O.) in a controlled environment (aquarium with no filtration).

2. Measure the amount of D.O. every 2C and record data.

Sample Data & Analysis and Interpretation

By looking at the data gathered, it appears the dissolved oxygen decreases at a steady rate for every two degrees Celcius increase. Once the temperature appears to have reached 30C, the dissolved oxygen decreases but at a slower rate when compare to earlier readings.

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