YSI 55 - Manual (Page 5)

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1. General Description
The YSI Model 55 Handheld Dissolved Oxygen System is a rugged, micro-processor based, digital
meter with an attached YSI dissolved oxygen probe.
The YSI Model 55 is designed for field use and is available with cable lengths of 12, 25 or 50 feet.
The body of the probe has been manufactured with stainless steel to add rugged durability and
sinking weight. The large Liquid Crystal Display (LCD) is easy to read and is equipped with a back-
light for use in dark or poorly lighted areas.
The Model 55's micro-processor allows the system to be easily calibrated with the press of a few
keys. Additionally, the micro-processor performs a self-diagnostic routine each time the instrument
is turned on. The self-diagnostic routine provides you with useful information about the function of
the instrument circuitry and the quality of the readings you obtain. For a list of these diagnostic
features, see chapter 7 Troubleshooting.
The system simultaneously displays temperature in o C and dissolved oxygen in either mg/L
(milligrams per liter) or % air saturation. The system requires only a single calibration regardless of
which dissolved oxygen display you use. You can switch back and forth from % air saturation to
mg/L with a single push of the MODE key.
A calibration chamber is built into the instrument. A small sponge in the chamber can be moistened
to provide a water saturated air environment which is ideal for air calibration. This chamber is also
designed for transporting and storing the probe. When the probe is stored in the chamber, the moist
environment will prolong effective membrane performance and probe life.
The instrument is powered by six AA-size alkaline batteries. A new set of alkaline batteries will
provide approximately 100 hours of continuous operation. When batteries need to be replaced, the
LCD will display a "LO BAT" message.
The YSI Model 55 instrument case is splash resistant. You can operate your Model 55 in a steady
rain without damage to the instrument.