YSI 5200A - Manual (Page 89)

YSI 5200A
176 YSI 5200A
177
Maintenance
It is important to remember that the quality of the data collected is dependent on
three factors directly related to the probe:
General maintenance at the physical deployment site of the probe as- -
sembly.
A well-defined quality assurance program that is carried out on a regular -
basis to ensure that the sensors are performing properly.
Proper periodic calibration and maintenance of the specific sensors. -
This chapter is designed to help in these important areas by providing maintenance
tips, help in implementing a quality assurance protocol, and suggested service
methods and intervals for the sensors.
Probe Maintenance at the Deployment Site
Algae and Debris
A common problem with regard to the overall probe assembly deployment site is
fouling from algae (and other debris). Algae will inevitably collect on any object
immersed in water and, unless periodically removed, it can inhibit the sensor’s
measurement. Once algae build-up occurs on the sensors and/or probe guard, it
isolates the sensor’s environment from the sample stream. To avoid or minimize
this problem, it is necessary to periodically remove the algae and biofouling from
the probe guard and sensors.
Minimizing the Effect of Algae and Debris
The collection of algae on the probe and the frequency of cleaning can be minimized
by deploying the probe so that it is angled with (rather than against) the current of
the stream. This deployment method will maximize the chances of the algae being
swept free from the probe rather than collecting on it.
Remember that no matter what precautions are taken, debris will still collect on the
probe and the fouling will have to be removed by periodic cleaning. Cleaning will
be easier if the probe mounting method allows for easy removal and replacement
of the probe. A little extra time spent implementing a good probe mount and using
the optional probe mounting kits will save time in subsequent probe cleanings.
The frequency in which you will have to remove fouling from the probe varies with
the type of water being monitored and the physical deployment of the probe. The
need for cleaning can usually be ascertained by visual inspection. You can do no
Maintenance
harm by excess cleaning so it is best to remove and clean the probe if any significant
fouling is suspected.
Calibration Checks
The sensors are of high quality and should exhibit excellent performance 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 chemi-
cal changes to the reagents in the probes, physical changes of the electrodes, and/
or minor fouling of the sensor surfaces. Noisy sensor readings (especially for the
conductivity and dissolved oxygen sensors) signal the need for maintenance pro-
cedures specific to those sensors. With these factors in mind, it is imperative that
you establish and carry out regular quality checks of the sensor readings to ensure
that they are within their specifications. The quality checks can help determine
when sensor maintenance or calibration is required.
Recommended Quality Assurance Protocol
This product has been designed and tested to provide trouble free service. How-
ever, as with all microprocessor based products, there is potential for failure which
could cause loss of control functions. Proper QC (Quality Control) procedures can
reduce the potential for failure.
It is recommended that you carry out the following quality assurance program
weekly during the initial use of the 5200A 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 quality checks
can be decreased. The procedure is relatively simple and should take only about
20 minutes to complete.
Take the following items to the deployment site: 1.
Bucket of clean water -
The small brush supplied with the conductivity sensor -
The calibration/storage cup supplied with the probe/cable assembly -
pH 7 buffer and another pH buffer (either pH 4 or pH 10) -
Latex gloves -
Place the 5200A in Service Hold mode. 2.
Remove the probe from the sample stream. 3.
CAUTION: The pH sensor should never be exposed to subfreezing air temperatures
for more than a few minutes.
Maintenance