YSI 58 - Manual (Page 10)

oxygen levels. When data is routinely collected with sample temperatures below 15
°C and at DO
levels below 20% air saturation, the low signal current resulting from the use if the standard
membranes tends to magnify the probe’s inherent constant background signal. Using the high
sensitivity membranes in this situation will decrease the percent error due to the probe’s background
current.
For long-term monitoring situations only, a half-sensitivity, double-thickness 2 ml (.002”) membrane
is available. Order the YSI Item # 5685 2 ml membrane, which includes membranes and electrolyte
for the 5718 and 5739 probes.
A selector switch inside the YSI 58 modifies the circuit for the membrane in use. This switch must be
set to the position corresponding to the membrane in use. Facing the back of the instrument, with the
back cover removed, the switch will be found on the top, right corner of the main PC board. Its
positions are labeled .5, 1 and 2 MIL. Also, See Section 4.4.2, Oxygen Measurements in Fluids
Other Than Water, for use of this switch in special measurement circumstances.
Membrane life depends on usage. However, if the electrolyte is allowed to evaporate and an excessive
amount of bubbles form under the membrane, or the membrane becomes damaged, thoroughly flush
the reservoir with electrolyte and install a new membrane.
If erratic readings are observed or calibration is stable, you need to replace the membrane.
The gold cathode should always be bright and untarnished. If it is tarnished, which can result from
contact with certain gases, or plated with silver, which can result from extended use with a loose or
wrinkled membrane, return it to YSI for service. You can also clean the gold cathode with the YSI
5680 Probe Reconditioning Kit. Never use chemicals or any abrasive other that what is supplied with
the kit. See Section 8 for contact information.
3.3.1 MEMBRANE INSTALLATION FOR THE 5239 PROBE
NOTE: The 5239 probe is shipped dry. A shipping membrane was installed to protect the electrodes.
A new membrane cap must be installed before first use.
Follow the steps below to install a membrane cap:
1. Unscrew and remove the probe guard. See figure 2.
2. Unscrew the old membrane cap and remove it from the probe.
3. Thoroughly rinse the entire area of the silver anode, gold cathode and threads with clean
water (distilled or deionized) to remove any dry crystals of the old electrolyte.
4. Hold the membrane cap and fill it with 6 to 7 drops of YSI standard electrolyte (KCl probe
solution) provided.
5. Tap the bottom of the membrane cap with your finger a few times (don’t touch the
membrane) to shake loose any trapped air bubbles.
6. Screw the membrane cap onto the probe moderately tight. A small amount of electrolyte
should overflow.
7. Rinse off the excess electrolyte with clean water.
8. Screw the probe guard onto the probe body.
9. Place the probe in the calibration bottle provided. Verify that sponge in the bottle is wet.
YSI Incorporated YSI 58 DO Meter 6