8
Water Action Volunteers – Level 2 Manual
Updated January 2016
YSI Model 550a Dissolved Oxygen (DO) Meter
The YSI 550a Dissolved Oxygen (DO) meter needs to be calibrated before being used in the field
each and every time you monitor. Once calibrated, the meter must be left on until you/your
team is done with monitoring activities for the day at all monitoring locations.
In order to avoid damaging the meter, do not let sponge inside the probe chamber dry.
Maintaining a damp environment in the chamber will help to ensure that your meter has high
quality performance throughout the field season. Keep sponge moist by re-wetting it, at least
bi-weekly, if not more frequently. If the sensor membrane becomes damaged, you will need to
replace it (contact the WAV coordinator for assistance) and then wait at least 1 hour before
calibrating and using the meter to monitor at your stream site.
Get to know your YSI 550A DO meter
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displays temperature in either °C or °F
and dissolved oxygen in either mg/L (milligrams per liter) or %
air saturation.
Power button
: powers the unit on or off.
Backlight button
: turns the display backlight on or off. The
light will turn off automatically after two minutes of non-use.
Mode button
: allows the user to select between % and mg/L
during calibration process. When monitoring, pushing ‘Mode’
switches the instrument display between DO %, DO mg/L, and
salinity calibration.
Arrow keys
: increases or decreases the value during
calibrations.
: enter button
Probe
: use to monitor water temp and dissolved oxygen content. Clean
the probe with DI water after each monitoring event and store in the
calibration chamber when not in use.
Maintaining your YSI 550A DO meter
Verify that the sensor membrane is in good condition by removing the sensor from the storage
chamber and check that the sponge is damp, if there are holes or tears in the membrane, and
for air bubbles beneath the membrane. If air bubbles or damage to the membrane is evident,
replace the membrane housing and solution. Ensure that membrane housing has been filled
with KCl solution for at least 1 hour before calibration and first use. Training videos for how to
calibrate the YSI 550A meter and monitor with it are available on the WAV website
(
http://watermonitoring.uwex.edu/wav/monitoring/video.html
). Please contact your local
coordinator or the WAV coordinator if you have any questions!
