YSI 58 - Manual (Page 9)

Four D-size carbon-zinc batteries that are housed in the lower battery compartment of the YSI 58
power the stirrer. When the stirrer will not be used for an extended period, these batteries should be
removed from the instrument.
3.2 PROBE INSTALLATION - YSI 5739
To disconnect the cable, unscrew the retaining nut and slide it down the cable to expose the
connector. Pull gently on the cable and connector until the connector comes away from the probe
body.
To reassemble, inspect the connector and O-Ring for cleanliness. If the O-ring is frayed or damaged,
remove it by squeezing it in the groove causing it to bulge, then roll it out of the groove and off of the
connector. A replacement O-ring is supplied with the cable.
Push the connector into the probe body, rotating it until the two halves match up. A VERY LIGHT
coating of silicone grease on the O-Ring will make reassembly easier.
CAUTION: DO NOT apply more than a light coating of grease, as it will attract dirt and particles that
may compromise the seal of the O-ring.
Air trapped between the connector halves that may cause them to spring apart slightly is normal.
Screw on the retaining nut, HAND TIGHTEN ONLY!
Note: If erratic readings are experienced, disconnect the cable and inspect for the presence of water. If
water is present, dry out and reconnect, replacing the O-Ring.
Pressure Compensation
The vent on the side of the probe is part of a unique pressure compensating system that helps assure
accurate readings at great depths of water. Pressure compensation is effective to 0.5% of reading with
pressures to 100psi (230 feet water). The quantity of air bubbles trapped under the membrane
determines how serious the pressure error will be, which is why proper preparation of the probe is
essential. See Section 4, Operation. The system is designed to accommodate a small amount of
trapped air and still function properly, but the amount should be kept to a minimum.
The compensating system normally does not require servicing and should not be taken apart.
However, if electrolyte is leaking through the diaphragm or if there is an obvious puncture, the
diaphragm must be replaced. A spare is supplied with the probe. Using a coin, unscrew the retaining
plug and remove the washer and diaphragm, flush any salt crystals from the reservoir, install the new
diaphragm (ridged side in), replace the washer and screw in the retaining plug.
3.3 CHOOSING THE CORRECT MEMBRANE
An extremely thin membrane increases O
2 permeability and probe signal current, and hastens a
probe’s response; but it achieves this at the cost of ruggedness. The membrane normally used with the
YSI 58’s probes is the 1 ml (.001”) membrane. This 1 ml membrane represents a compromise
between quickness of response, and membrane strength and integrity.
For special circumstances, a 0.5 ml (.0005”) membrane is available. This half-thickness membrane
hastens response at low temperatures and helps suppress background current at very low dissolved
YSI Incorporated YSI 58 DO Meter 5