In-Situ TROLL 9500 Operators Manual - Manual (Page 72)

65 TROLL 9500 Operator’s Manual 0095110 rev. 007 01/09
WHEN TO REPLACE A SENSOR
After a certain amount of use even a complete recalibration will not
be able to accurately calculate calibration coefficients. The slope will
gradually become lower and lower. At this point the sensor should be
replaced. Specific slope guidelines for individual sensors are given in
the individual parameter sections below.
USING A STIRRER
In-Situ’s stirrer accessory provides continuous sample circulation or
agitation, which can improve the performance of water-quality sensors
in a number of applications.
Dissolved oxygen (DO) measurements drop in very stagnant water
due to depletion of oxygen next to the membrane. A slight perturbation
to the system will cause the DO measurements to return to normal.
Stirring is recommended if the instrument is anchored to a fixed struc-
ture in stagnant conditions—for example, attached to a pier in a calm
lake that has no underwater currents. If the wind is blowing and waves
are slightly moving the cable, then stirring is probably not necessary.
ISE sensors in close proximity to each other can sometimes create
interferences. Constant stirring can enhance the performance of the
ISE sensors.
Sample agitation can also help to improve sensor response time
when water-quality conditions are subject to change (e.g., in a moving
contaminant plume) and can speed up temperature stabilization.
Attaching the Stirrer for Field Use
The stirrer accessory is easily installed on the MP TROLL 9000. See
illustration D earlier in this section.
1. Remove the nose cone from the MP TROLL 9500. Leave the
restrictor attached to the instrument.
2. Screw the top of the stirrer (propeller end) to the stainless steel
restrictor in place of the nose cone.
3. Start the stirrer; see Starting the Stirrer earlier in this section.
The instrument is ready for use in stagnant water.
SECTION 10: MONITORING WATER QUALITY: OVERVIEW
Q:
A:
How can I find the serial number of a water quality sen-
sor—pH for example?
The software can display the sensor serial number. Do this:
1 Select pH in the Navigation tree
2 Look at the information displayed The serial number is
displayed in the Information pane on the right side of the
screen (or at the bottom on a PDA)
REFERENCES
Eaton, A.D., L.S. Clesceri, E.W. Rice, and A.E. Greenberg, eds.,
Standard Methods for the Examination of Water and Wastewater,
21st edition, Washington, D.C.: American Public Health Associa-
tion, American Water Works Association, and Water Environment
Federation, 2005.
A Fish Farmer’s Guide to Understanding Water Quality. LaDon
Swann, Dept. of Animal Sciences, Illinois-Indiana Sea Grant
Program, Purdue University. On the web at AquaNIC (Aquaculture
Network Information Center), aquanic.org.
Rundle, Chris C., A Beginners Guide to Ion-Selective Electrode
Measurements. Nico2000 Ltd., London, UK. On the web at www.
nico2000.net
Water on the Web (WOW). University of Minnesota project initially
funded by the National Science Foundation. On the web at wow.
nrri.umn.edu
Pressure Rating Usable Depth
Sensor PSI Meters Feet
pH 300 210 692
pH/ORP 300 210 692
Conductivity 350 246 807
$/
Turbidity 350 246 807
Wiper 350 246 807
Chloride 100 70 231
Ammonium 20 14 46
Nitrate 20 14 46
RDO exceeds rating of the TROLL 9500
Water Quality Sensor Pressure Ratings
* Submersion and retrieval at up to 4 feet per second.