4220 Flow Meter
Section 5 Options and Accessories
tap water could revive the electrode in more severe situations. If none of these solutions work, it may be necessary to replace the probe.
5.10 The Dissolved Oxygen |
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(D.O.) Probe | Note |
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The 270 D.O. module has been discontinued. Probes, service kits, and accessories are still available to maintain existing field units.
This probe measures the amount of oxygen dissolved in a stream or waterway. Oxygen dissolved in water is necessary for many forms of life that dwell in lakes and streams. Inadequate supplies of dissolved oxygen will cause fish and other aquatic life that depend on them as a food source to die off or be sharply dimin- ished in numbers. The measurement of dissolved oxygen content is of interest to those monitoring the condition of lakes and streams. Fish must have a certain minimum concentration of dis- solved oxygen to thrive, typically 4 to 6 mg/l.
Various types of pollution can cause the amount of oxygen dis- solved in water to drop sharply, placing the aquatic life forms at serious risk. The D.O. probe measures the amount of oxygen dis- solved in water in a range from 0 to 20 mg/l. Note that the flow meter can display D.O. in either mg/l (milligrams per liter) or ppm (parts per million) depending on your choice in pro- gramming.
Figure 5-5 The D.O. Probe
For effective use of the D.O. Probe, please read and con- sider the following before making the installation:
•The D.O. Probe requires constantly moving water. The probe consumes oxygen during operation; this will deplete the oxygen available from stagnant or stratified waters, resulting in an inaccurate reading. Do not install it in a stilling well or in any location where water movement is intermittent or very low. As a guideline, a minimum velocity of one foot per second is suggested.
•Frequent maintenance is necessary when the probe is installed in flows with grease or solids content.
