YSI 556 MPS - Manual (Page 99)

Maintenance Section 11
YSI Incorporated YSI 556 MPS Page 93
Probe Sensor
Guard
Set Screw
DO Sensor
Hex Key
Wrench
F igure 11.1 DO Sensor Replacement
4. Insert the new DO sensor module. Make sure that the inside
of the probe module sensor port and the o-ring on the sensor
are clean, with no contaminants, such as grease, dirt, or hair.
The DO sensor is keyed, or has a flat side, so that it cannot be
aligned improperly.
NOTE: Make sure the DO sensor bottoms out before the set
screw is inserted.
5. Insert the set screw into the small hole in the side of the probe
module bulkhead, and turn clockwise to rethread.
CAUTION: Make sure that you do not cross-thread the set
screw. Use the hex key wrench to tighten the screw in properly,
making sure that the screw does not stick out of the side of the
probe module bulkhead. The probe sensor guard will not thread
on properly and damage may result if the screw is allowed to
stick out.