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recorded. Select the longest interval that will show the changes in turbidity and
water depth that you wish to investigate. Rate sets measurement frequency.
The quicker turbidity and depth change, the higher the sampling rate should be
to get a stable average value for a sample. Finally, Duration sets how long
sensor outputs will be averaged. For example, with an interval of 30 seconds
and a duration of five seconds, the OBS-5+ will make measurements for five
seconds starting every 30 s. The sample size would be 5 x 25 = 125
measurements for a rate of 25 Hz. Always select duration and rate to give a
sample size of at least 30, and to reduce random sampling noise below 50% of
its maximum value, select them to give a size greater than 200.
connection to a PC and when high data rates are desired. Data can be logged
with a PC at rates up to 120 lines per minute (2 Hz).
MB, flash memory at regular intervals; for example, every 1, 5, 15, or 30
minutes. Depending on the number of sensors measured and the statistics
selected, the OBS-5+ can log as many as 200,000 lines of data, one per hour
for 23 years, including time, date, depth, NTUs, and SSC.
6.2.10 Surveying
Click the OBS-5+ menu and select Barometric Correction.
Do not do this while the OBS-5+ is submerged.
CAUTION
The OBS-5+ takes about five seconds to measure the surface pressure and
compute a barometric correction.
1) Connect the OBS-5+ to PC with survey cable and start OBS-5+ Utility.
2) Open the Data Window with the View pull-down menu.
Survey: Select the survey mode when operating the unit with a cable
Cyclic Sampling: Use cyclic sampling to record data internally in the 8
OBS-5+ System
15
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