YSI 6500 Environmental Process Monitor - Manual (Page 53)

Proper Use and Care of the 6500
Section 5
7. Replace the sonde guard.
8. Place the sonde in enough pH 7 buffer to immerse the pH probes. Wait about 3 minutes for
the sensor to stabilize in the new medium and record the reading shown on the 6500 Monitor
display. The deviation from pH 7 will reflect the sensor drift during the deployment period.
9. Activate the 2-point pH calibration protocol from the 6500 display and recalibrate the
instrument using the two buffers as described in Section 2, Sondes, of the 6-Series Sonde
Operations Manual.
10. Rinse the sonde with water and place in the vented storage bottle containing about 1/8 inch
(3 mm) of water. Make sure that the dissolved oxygen sensor is not immersed in the water.
11. Wait about 5 minutes for temperature equilibration and then record the dissolved oxygen
reading in percent air saturation as shown on the 6500 display. The deviation from the
current barometer reading will reflect the sensor drift during the deployment period.
12. If the dissolved oxygen readings show minimal drift (within about 5 % of the correct value)
and are stable, proceed with step #12. If excessive drift is noted or the readings are jumpy,
remove the membrane and resurface the sensor as described in Section 2, Sondes, of the 6-
Series Sonde Operations Manual. Then reinstall new electrolyte and a new membrane and
proceed, allowing a 10-15 minute break-in period before actually implementing a new
calibration.
13. Activate the DO % calibration protocol from the 6500 display and recalibrate the instrument
to the current local barometric pressure.
14. Replace the sonde in the stream and continue monitoring.
NOTE: The procedure does not include quantitative data taken with regard to either the
temperature or conductivity sensors. The temperature sensor only fails in very rare circumstances
and, when it does, the temperature readings will seem unreasonable for the current conditions. In
the unlikely event that the temperature sensor shows unusual and/or jumpy readings, the # 6560
conductivity/temperature (or the 600R sonde) will need to be checked by authorized service
personnel. No user service is possible. For the conductivity sensor, drift is usually minimal
except as caused by build-up of debris in the cell. Once this is cleaned out as described in Step 4
of the above protocol, the sensor almost always yields accurate readings again with no
recalibration needed. However, if you wish to check your conductivity calibration, place the
sonde in a known standard being sure that the top vent hole is completely covered. If significant
drift has occurred, recalibrate the sensor as described in Section 2, Sondes, of the 6-Series Sonde
Operations Manual.
ALTERNATIVE QUALITY ASSURANCE PROTOCOL (QUICK CHECK AND
ADJUSTMENT)
An alternative, complementary type of quality assurance program to that described above for the
6-Series sensors can be carried out by comparing the current dissolved oxygen and pH readings
YSI Incorporated 6500 Environmental Process Monitor 50