OBS501 Smart Turbidity Meter with ClearSensor
®
Technology
30
10.
Perform 3
rd
order polynomial regressions on the data to get the coefficients
for converting OBS output to SSC.
8.7 Operation in High Sediment Loads and Sandy Sediments
Sites with high sediment loads and large sand grains can be problematic for the
shutter and its motor. The recommendations provided in this section should
help reduce these problems.
Typically sites with high biological growth have relatively low
sediment loads.
1.
Run the OBS501 in a normally open mode. For example, close then open
the wiper once every four hours. This reduces the wear on the motor
significantly, and saves power. The interval can be adjusted over time.
Increase the interval if experiencing fouling. If the windows are staying
clean, slow it down even more. Example CRBasic programs are provided
at Appendix
Examples for High Sediment Loads
(p. B-5)
a.
aM3!
opens the wiper
b.
aM4!
,
aM5!
, or
aM6!
perform measurements when the wiper is open
c.
aM7!
closes the wiper
2.
Clean the shutter assembly. The frequency that the shutter should be
cleaned depends on the sediment load and can vary from weeks to months
(step 3 can help you determine the required frequency for cleaning). Two
levels of cleaning should be done:
a.
flush the wiper as it opens and closes with a stream of clean water, or
b.
remove the wiper from the OBS501 by removing one screw and
follow the directions provided in Section
(p. 30)
. Flush and clean.
3.
Store the current used to open and close the slider. The open and close
SDI-12 instructions (
M3!
and
M7!
) output the current. Normally the
current is around 100 mA. As sand grits lodge in the groves, the resistance
to movement increases and the motor has to work harder. This increases
the current usage. Therefore, increased current usage indicates that the
wiper needs to be cleaned (see step 2).
4.
Mount the sensor between 45 degrees pointing down to vertical hanging
down.
8.7.1 Wiper Removal Procedure
1.
Remove the stop screw in the OBS501 housing at the end of the
shutter/wiper slot.
2.
Remove the 4-40 flat head screw and copper plate to expose the drive shaft
access port (FIGURE
NOTE
