YSI PRO20 User Manual page 38

Symptom
Instrument readings are inaccurate.
Dissolved Oxygen values display
Over or Undr on run screen.
Possible Solution
1) Verify correct sensor/membrane type
selection in the System Setup menu.
2) Verify calibration, barometer reading,
and salinity settings are correct and
recalibrate.
3) Verify accurate temperature readings.
4) Sample temperature is over 45 ºC, the
temperature compensation range.
5) Probe may not have been in 100%
water saturated air during calibration
procedure. Moisten sponge in
calibration sleeve and recalibrate.
6) Replace membrane and electrolyte,
recalibrate.
7) Clean sensor electrodes.
8) Return system for service.
1) Verify correct sensor/membrane type
selection in the System Setup menu.
2) If using a polarographic sensor, allow
instrument to warm up for 5 – 15
minutes before use.
3) Sample O concentration is more than
2
50 mg/L or 500%, or less than –0.02
mg/L or -0.3%.
4) Verify barometer and salinity settings
are correct and recalibrate.
5) Verify accurate temperature readings.
6) Replace membrane and electrolyte.
Recalibrate.
7) Clean sensor electrodes.
8) Return system for service.
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