Xylem ODO RTU User manual

ODO RTU™User Manual
OPTICAL DISSOLVED OXYGEN & TEMPERATURE SENSOR
USER MANUAL
ITEM# 627379-01
REVISION A

The information contained in this manual is subject to change without notice.
Effort has been made to make the information in this manual complete, accurate, and current.
The manufacturer shall not be held responsible for errors or omissions in this manual.
Consult YSI.com for the most up-to-date version of this manual.
Thank you for purchasing a YSI ODO RTU dissolved oxygen probe. This manual covers setup, operation, and functionality.
Safety Information
Please read this entire manual before unpacking, setting up or operating this equipment. Pay attention to all precautionary
statements. Failure to do so could result in serious injury to the operator or damage to the equipment. Do not use or install this
equipment in any manner other than that specified in this manual.
The manufacturer is not responsible for any damages due to misapplication or misuse of this product including, without limitation,
direct, incidental and consequential damages, and disclaims such damages to the full extent permitted under applicable law. The
user is solely responsible to identify critical application risks and install appropriate mechanisms to protect processes during a
possible equipment malfunction.
A
A
NOTICE: Indicates a situation which, if not avoided, may cause damage to the instrument
Precautionary Symbols
Product Components
Carefully unpack the instrument and accessories and inspect for damage. If any parts or materials are damaged, contact YSI
Customer Service at 800-897-4151 ([phone]) or the authorized YSI distributor from whom the instrument was purchased.
NOTE: Information that requires special emphasis
WARNING: Indicates a potentially or imminently hazardous situation which, if not avoided, could result in death
or serious injury
CAUTION: Indicates a potentially hazardous situation that may result in minor or moderate injury

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TABLE OF CONTENTS
1. Introduction
1.1 Probe Assembly
1.2 Preparing the Probe and Sensor
2. Setup
2.1 Wiring
2.2 Power
3. Calibration
3.1 Calibration Setup
3.2 Conductivity
3.3 Dissolved Oxygen
4. Maintenance and Storage
4.1 Conductivity Sensor
4.2 Optical Dissolved Oxygen Sensor
5. Modbus Configuration & Commands
5.1 Modbus Serial Configuration
5.2 Device Information
5.3 Data
5.4 Calibration
5.5 User Values for Derived Parameters
5.6 Conductivity Settings
5.7 Appendix A: Register Mapping Tables
6. Accessories
6.1 Ordering
7. Safety and Support
7.1 Service Information
7.2 Technical Support
7.3 Declaration of Conformity
7.4 Warranty
8. Appendices
8.1 Appendix B - DO% Calibration Values
8.2 Appendix C - Oxygen Solubility Table

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Introduction
1.1
1. Introduction
1.2
Probe Assembly
Preparing the Probe and Sensor
ODO RTU assemblies feature integral sensors — this means that these sensors cannot be removed from the probe and cable. Sensor
caps are user-replaceable and need to be changed out about once per year.
NOTE: Each ODO cable assembly and sensor cap includes an instruction sheet with important information unique and
specific to each individual sensing cap. These are important because they include calibration coefficients needed for
proper setup.
NOTE: A new cable/probe assembly already has a sensor cap installed and the sensor cap coefficients are preloaded into
the probe at the factory.
1. Remove the metal probe guard from the probe by turning it counterclockwise.
2. Remove the red storage cap which, contains a moist sponge, from the end of the probe by pulling it straight off the sensor.
Save this to use later for long-term storage.
3. Reinstall the probe guard by sliding it carefully over the sensor and then threading it onto the cable assembly with a
clockwise rotation.
CAUTION: It is important to always store your sensor in a moist environment so the sensor cap does not dry out. A grey
calibration/storage sleeve is shipped with your cable assembly for an easy storage option. Simply moisten
the sponge with a small amount of clean water and slide the sleeve over the probe guard to create a moist
atmosphere for the sensor.
Figure 1 ODO probe and cable assembly
1 Probe
2 Sensor
3 Sensor Cap
1
2
3
A

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Setup
2.1 Wiring
2. Setup
ODO RTU is configured with native Modbus output built around the RS485 standard physical layer. The flying lead cable is
terminated with its ends trimmed and tinned for easy wiring. These ends can be connected to a third party Modbus capable PLC
or data logger.
Wire Color Purpose
Red Power
Green Ground
White Modbus A
Black Modbus B
2.2 Power
ODO RTU requires 10-16 VDC with a maximum current of 15 mA. The sensor will pull 0.12 W while powered. Once power is
supplied to the sensor, the probe will complete a 1-2 second power up sequence before it can be queried for a value. Please note,
while the probe can return a value, if the sensor cap is not equilibrated, the returned value may be inaccurate. This is not an issue if
the sensing cap has been continuously submerged in the sample.

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Calibration
3.1
3. Calibration
ODO RTU requires periodic calibration. Calibration procedures follow the same basic steps with variations for the specific
parameter. The specific Modbus commands that accompany the calibration can be found in the Modbus Configuration and
Commands section of this document
Make sure the calibration cup, sensor guard, and all sensors are clean. YSI strongly recommends installing the sensor guard before
placing the sensors into the calibration cup.
For highest data accuracy, thoroughly rinse the calibration cup and sensors with a small amount of the calibration standard for the
sensor to be calibrated. Discard the rinse standard, and proceed with a fresh standard.
Be careful to avoid cross-contamination with other standards between calibrations by thoroughly rinsing with DI water and drying
the calibration cup and sensors.
Calibration Setup

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Calibration
3.2 Conductivity
If installed, the conductivity/temperature sensor can measure and calculate conductivity, specific conductance (temperature
compensated conductivity), salinity, non-linear function (nLF) conductivity, TDS, resistivity, and density. Calibration is only
available for specific conductance, conductivity, and salinity. Calibrating one of these options automatically calibrates the other
conductivity/temperature parameters listed above. For both ease of use and accuracy, YSI recommends calibrating specific
conductance.
Select the appropriate calibration standard for the conductivity of the sampling environment. Standards at least 1 mS/ cm (1000
μs/cm) are recommended for the greatest stability. For fresh water applications, calibrate to 1,000. For salt water applications,
calibrate to 50,000 μS.
Conductivity Calibration
1. Make sure the conductivity sensor is clean prior to calibration. If necessary,
clean the conductivity cell with the supplied soft brush.
2. Place the correct amount of conductivity standard into a clean and dry or
pre-rinsed calibration cup.
3. Carefully immerse the sensors into the solution. Make sure the solution is
above the vent holes on the side of the conductivity sensor.
If using the ODO/CT assembly, ensure the vent holes at the top of the
sensor are completely immersed and the solution level is at least 1 cm
higher than the top vent holes (Figure 2). A graduated cylinder is included
with ODO/CT cable assemblies for the purpose of calibrating conductivity.
4. Gently rotate and/or move the sensor up and down to remove any
bubbles from the conductivity cell. Allow at least 40 seconds for
temperature equilibration before writing the value with the appropriate
Modbus command (see Modbus Configuration and Commands for
more details).
5. Rinse the sensor in clean water then dry.
NOTE: If the data is not stabilized after 40 seconds, gently rotate
the sensor or remove/reinstall the calibration cup to make
sure that no air bubbles are in the conductivity cell.
If you get calibration error messages, check for proper
sensor immersion, verify the calibration solutions is fresh,
the correct value has been entered into the handheld, and/
or try cleaning the sensor.
Figure 2 ODO/CT Cable Assembly
Top Vent
Holes
Side Vent
Holes

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Calibration
3.3 Dissolved Oxygen
ODO calibration requires the current “true” barometric pressure. Make sure that the barometric pressure has been input properly
and accurately prior to ODO calibration. See Modbus Configuration and Commands for more details.
ODO% - Water Saturated Air Calibration
1. Place a small amount of clean water (5 mL) in the calibration cup or a wet
sponge into the calibration sleeve (Figure 3).
2. Make sure there are no water droplets on the ODO sensor cap or
temperature sensor.
3. Attach the probe guard and carefully slide into the calibration cup. Make
sure a seal is not created around the probe. Atmospheric venting is
required for accurate calibration.
4. Turn the instrument on and wait approximately 5 to 15 minutes for the air
in the storage container to be completely saturated with water.
5. Allow at least 40 seconds for equilibration before writing the value with
the appropriate Modbus command (see Modbus Configuration and
Commands for more details).
ODO mg/L Calibration
1. Place the ODO and conductivity/temperature sensor into a water sample
that has been titrated by the Winkler method to determine the dissolved
oxygen concentration in mg/L.
2. Enter the dissolved oxygen concentration of the sample in mg/L.
3. Allow at least 40 seconds for equilibration before writing the value with
the appropriate Modbus command (see Modbus Configuration and
Commands for more details).
4. Rinse the bulkhead and sensors in clean water then dry.
ODO Zero Point Calibration
1. Place the sensor in a solution of zero DO.
NOTE: A zero DO solution can be made by dissolving approximately 8-10
grams of sodium sulfite into 500 mL of tap water. Mix the solution
thoroughly. It may take the solution 60 minutes to be oxygen-free.
2. Allow at least 40 seconds for equilibration before writing the value with
the appropriate Modbus command (see Modbus Configuration and
Commands for more details).
3. Thoroughly rinse the bulkhead and sensors in clean water then dry.
4. Perform a ODO % water-saturated air calibration after performing a zero
point calibration.
Figure 3 ODO Cable Assembly in
calibration sleeve

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Maintenance and Storage
4.1
4. Maintenance and Storage
Follow all maintenance and storage procedures in this section. Incorrect or unapproved maintenance and/or storage can cause
sensor or cable damage not covered by the warranty.
Storage terms are defined as follows:
Short-term Storage = Less than 4 weeks
Short-term storage is appropriate when the cables, and sensors will be used at regular intervals (daily, weekly, etc.).
Long-term Storage = More than 4 weeks
During long periods of inactivity, such as the “off-season” for environmental monitoring, the instrument, sensors, and cables should
be placed in long-term storage.
YSI recommends cleaning and maintenance before long-term storage.
The conductivity channels should be cleaned after each use. Dip the sensor’s
cleaning brush (included with the maintenance kit) in clean water, insert the brush
at the top of the channels, and sweep the channels 15 to 20 times (Figure 4).
If deposits have formed on the electrodes, use a mild solution of dish soap and
water to brush the channels. For heavy deposits, soak the sensor in white vinegar,
then scrub with the cleaning brush. Rinse the channels with clean water following
the sweepings or soak.
The ODO/CT probe must be stored in a moist environment.
Conductivity Sensor
Figure 4 Channel brush

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Maintenance and Storage
4.2 Optical Dissolved Oxygen Sensor
The ODO sensor should be kept clean since some types of fouling may consume
oxygen which could affect the dissolved oxygen measurements.
To clean the sensor cap, gently wipe away any fouling with a lens cleaning tissue
that has been moistened with water to prevent scratches (Figure 5). Do not clean
the ODO sensor with organic solvents as they may damage the cap.
To minimize sensor drift, always store the ODO sensor in a wet or water-saturated
air environment.
Figure 5 Wiping the ODO
sensor window
Figure 6 ODO short-term storage
Short-term Storage:
Store the ODO sensor in a moist air environment. A storage sleeve with a wet
sponge or the calibration cup with a small amount of water is recommended.
Long-term Storage:
• Method 1: Submerge the sensing end of the sensor in a container of distilled
or deionized water. Periodically check the level of the water to make sure that it
does not evaporate.
• Method 2: Wet the sponge located in the cap originally included with the
ODO sensor, then install on sensing end of the ODO sensor. Replace the
sponge if it becomes dirty.
A grey storage sleeve is shipped with the cable for an easy storage option. Simply
moisten the sponge with a small amount of clean water and slide the sleeve over
the probe guard to create a moist atmosphere for the sensor.
ODO Sensor Rehydration
If the ODO sensor has accidentally been left dry for longer than 8 hours, it must
be rehydrated. To rehydrate, soak the ODO sensor in room temperature tap water
for approximately 24 hours. After the soak, calibrate the sensor.
Figure 7 ODO rehydration