YSI 600LS - User Manual - Manual (Page 318)

Turbidity Measurements Appendix E
YSI Incorporated Environmental Monitoring Systems Operations Manual E- 5
2. The probe is experiencing “interference” from the calibration cup bottom during the zero point
calibration. This “interference” can due to (a) improperly using a calibration cup with a gray (rather
than black) bottom; (b) using a calibration cup with a black bottom which has been contaminated with
impurities; or (c) having the probe too close to a the calibration cup bottom. To overcome (a), be sure
to use install the black bottom that came with your 6136 into your calibration cup. To overcome (b)
be sure that the black bottom of the calibration cup is clean before performing a calibration. To
overcome (c), make certain that you engage only ONE THREAD when screwing the calibration cup
onto the sonde in order to keep the turbidity probe face as far as possible from the calibration cup
bottom to avoid interference. To completely overcome the “interference” problem, use the extended
length calibration cup (#116275 for 6600-style sondes and #069310 for 6820/6920-style sondes).
Note, however, the longer calibration cups will require larger volumes of calibration standard.
You might observe readings during sampling which appear unreasonable from visual inspection of
the water. Bubbles on the optics of the sensor usually cause the problem. Activate the wiper to remove
the bubbles. If the readings are still unreasonable, remove the sonde completely from the water and then
replace in the water. If problems are still evident, remove the sonde guard and check general probe
function by placing your finger or thumb over the optics as described above. If the probe does not respond,
contact YSI Technical Support.
You might see readings during sampling that you think are too jumpy. If this occurs, the water may be
non-homogeneous with regard to the size of the suspended particles. The jumpiness that you are observing
is probably real. However, if you want to smooth it out, you can incrementally increase the Time Constant
and Threshold settings in the Data Filter menu to obtain the noise level which you desire.
You might observe single point spikes in data from deployment applications. These high readings may
be real turbidity events caused by large particles passing over the optical surface at the time of
measurement. As long as the spiking occurs only occasionally, there is no reason to believe that the
turbidity system is malfunctioning. Depending on the site, these spikes may be a normal occurrence.
You might see a lot of unreasonable high spikes in data from deployment applications. This symptom
usually results from improper activation or parking of the wiper assembly. If it occurs with a new wiper
assembly, make certain that the wiper rotates and parks correctly (opposite the optical surface) in 0 NTU
standard. If the wiper does not rotate at all, be certain that the setscrew of the assembly is contacting the
flat part of the shaft and that the screw is securely tightened using the small hex key that is supplied with
the wiper assembly. If the wiper still will not rotate on manual activation, contact YSI Technical Support.
If the problem occurs with a wiper assembly which has been in the field for some time and is discolored or
abraded, install a replacement wiper with a new pad, assure function and correct parking in 0 NTU
standard, and redeploy. If a high frequency of spikes still occurs in the deployment data, contact YSI
Technical Support for further assistance.