YSI 5200A - Manual (Page 93)

YSI 5200A
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YSI 5200A
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CAUTION: The pH sensor should never be exposed to subfreezing air temperatures
for more than a few minutes.
5. Remove the probe guard from the probe.
6. Remove any debris from the sensors and then rinse carefully in a bucket
of clean water, being very careful not to damage the sensors.
7. 5562 probe assembly only: Using the small round brush provided with
the sensor, repeatedly scrub the two open holes in the conductivity sensor.
See figure 4.5 page 76.
8. While the probe guard is removed, inspect the dissolved oxygen membrane
for obvious holes or tears. Do not remove the membrane cap at this time.
9. Replace the probe guard.
10. Exit Service Hold if Service Hold timer has not expired. See pages 128
and 169 for Service Hold information .
11. 5562 probe assembly only: Place the probe in enough pH 7 buffer to
immerse the pH and temperature sensor. Wait about 3 minutes for the
readings to stabilize and record the reading shown on the 5200A. The
deviation from pH 7 will reflect the sensor drift since the last calibration.
12. 5562 probe assembly only: If necessary, i.e. pH sensor exhibits large drift
from last calibration, perform a two-point pH calibration. See pH calibra-
tion starting on page 83.
13. Rinse the probe with water and then place it into the calibration/storage
cup containing about 1/8 inch (3 mm) of water or a moisten sponge. Make
sure that the dissolved oxygen sensor is not immersed in the water and
that there are no water droplets on the membrane.
14. Wait about 5 minutes for temperature equilibration and then record the
dissolved oxygen reading in percent air saturation as shown on the 5200A
display.
15. If the dissolved oxygen readings show minimal calibration drift (i.e.,
within about 5% of the correct value) and the readings are stable, proceed
to Step #18. If excessive drift is noted or the readings are jumpy, replace
the membrane cap as described in the instruction sheet included in the
Membrane Kit.
16. After replacing the membrane, calibrate the DO sensor. See calibrate DO
sensor starting on page 79.
17. 5562 probe assembly only: Validate ORP value by placing probe assembly
in solution of known ORP value. If ORP sensor exhibits large drift from
last calibration, perform sensor calibration. See ORP calibration page 82.
18. Place the probe back in the sample stream and continue monitoring.
19. Test all control and alarm relays for proper operation.
NOTE: This procedure does not include quantitative data taken with regard to
either the temperature or conductivity sensors. The temperature sensor only fails
Maintenance
in very rare circumstances and, if it does fail, the temperature readings will seem
unreasonable for the current conditions. In the unlikely event that the temperature
sensor shows unusual and/or jumpy readings, it will need to be checked by a YSI
authorized service center. No user service is possible. For the conductivity sensor,
drift is usually minimal except as caused by build-up of debris in the sensor. Once
the sensor is cleaned as described in Step 5, the sensor almost always yields accurate
readings. However, if you wish to check your conductivity calibration, place the
probe in a known standard being sure that the top vent hole is completely immersed.
If significant drift has occurred, recalibrate the sensor.
Alternative Quality Assurance Protocol (quick check and
adjustment)
An alternative protocol, complementary to the quality assurance program already
described, can be carried out by comparing the current dissolved oxygen and pH
readings shown on the 5200A with those taken by a recently calibrated hand held
instrument. For dissolved oxygen, the probe of a handheld DO instrument can
be placed in the stream near the 5200A probe. If a comparison of the readings
from the recently calibrated DO instrument and the 5200A indicates calibration
drift, the 5200A can be recalibrated. Note - this comparison should only be used
to determine if a calibration is necessary once the 5200A probe has been cleaned
of all algae and other debris. If a gross variation is observed between the two
instruments (> 1 mg/L), it is likely that maintenance is required on the 5200A DO
sensor.
For pH, a similar field calibration adjustment can be made using a field pH meter.
Sensor Care and Maintenance
Periodic sensor cleaning and DO membrane changes are required.
DO Sensor
The DO sensor requires periodic membrane changes and electrode cleaning. For
best results, YSI recommends that the electrolyte (02 probe) solution and the
membrane cap be changed at least once every 30–90 days. Refer to the instruc-
tion sheet included with the membrane kit for specific instructions on changing a
membrane.
Notes
- Membrane life depends on usage. Membranes will last a long time if
installed properly and treated with care. Erratic readings are a result of
Maintenance