YSI 5200 - Manual (Page 110)

YSI Incorporated 108 5200 Recirculating System Monitor
11.2 Calibration Checks
The sensors are of high quality and should exhibit excellent performance in your application in excess of
the warranty period. However, the dissolved oxygen, pH, ORP and conductivity sensors will inevitably
show some drift during deployment due to natural chemical changes to the reagents in the probes,
physical changes of the electrodes, minor fouling of the sensor surfaces, or all of these factors. Noisy
sensor readings (especially for the conductivity and dissolved oxygen sensors) signal the need for specific
maintenance procedures. With these factors in mind, it is imperative for you to establish and carry out
regular checks of the quality of your sensor readings in order to assure that they are performing within
their specifications.
11.3 Recommended Quality Assurance Protocol
This product has been designed and tested to provide trouble free service. However, as with all
microprocessor based products, there is potential for failure which could cause loss of control functions.
Proper QC procedures can reduce the potential for failure.
We recommend that you carry out the following quality assurance program weekly during the initial use
of your 5200 system. After several weeks of this program, you should be able to ascertain if this
frequency is appropriate for your application. If only minimal drift is observed, then the frequency of
implementing the protocol can be decreased. The procedure is relatively simple and should take only
about 20 minutes to complete.
1. Take the following items to the deployment site:
Ö Bucket of clean water
Ö The small brush supplied with the conductivity sensor
Ö The calibration/storage cap supplied with the Probe
Ö pH 7 buffer and another pH buffer (usually pH 4 or pH 10) of your choice
Ö Latex gloves
2. Press the Enter [  ] key two times to place the 5200 in Service Hold mode. Remember that all
relays will return to their default state.
3. Remove the probe from the sample stream.
WARNING: The pH sensor should never be exposed for more than a few minutes to subfreezing
air temperatures.
4. Remove the probe guard from the probe.
5. Manually remove any gross debris from the sensors and then rinse carefully in a bucket of clean
water, being very careful not to damage the sensors.
6. (5562 Probe only) Using the small brush provided with the sensor, repeatedly scrub the two
conductivity channels. After brushing is complete, rinse the sensor with clean water.
7. 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.
8. Replace the probe guard.
9. (5562 Probe only) Place the probe 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 5200
Monitor display. The deviation from pH 7 will reflect the sensor drift during the deployment
period.