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

3
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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

4
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

5
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.

6
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

7
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

8
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

9
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

10
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

11
Maintenance and Storage
ODO Sensor Cap
Optical DO Extended Warranty Sensor Caps [SKU: 627180] are warrantied for 24 months. Depending on usage and storage
practices, the cap may last longer than its warranty period.
As the ODO sensor caps ages, deterioration of the dye layer can reduce measurement stability and response time. Periodically
inspect the sensor cap for damage and large scratches in the dye layer. Replace the cap when readings become unstable and
cleaning the cap and DO recalibration do not remedy the symptoms.
Figure 8 ODO cap replacement
ODO Sensor Cap Replacement
The instruction sheet shipped with the replacement ODO sensor cap includes
the calibration coefficients specific to that sensor cap. Make sure to save the
ODO sensor cap instruction sheet in case you need to reload the calibration
coefficients.
1. Remove the old sensor cap assembly from the probe by grasping the
probe body with one hand and rotating the sensor cap counterclockwise
until it is completely free. Do not use any tools for this procedure.
2. Carefully remove the o-ring by pinching it with your fingers and rolling
it up. Do not use any tools to remove the o-ring. Clean the area of any
debris with a lens cleaning tissue.
3. Install the new o-ring that is included with the replacement sensor cap.
4. Apply a thin coat of o-ring lubricant (included with the new cap) to the
installed o-ring. Remove any excess o-ring lubricant with a lens cleaning
tissue. Be careful to avoid contact with the sensor lens.
5. Inspect the sensor lens for any moisture or debris. If necessary, wipe the
lens carefully with a non-abrasive, lint-free cloth to prevent scratches. Do
not use organic solvents to clean the ODO sensor lens.
6. Remove the new sensor cap from its hydrated container and dry the inside
cavity of the sensor cap with lens cleaning tissue. Make sure the cavity is
completely dry before proceeding with the installation.
7. Using clockwise motion, thread the new sensor cap onto the probe
assembly until it is finger-tight. The o-ring should be compressed between
the sensor cap and probe. Do not over-tighten the sensor cap and do not
use any tools for the installation process.
8. After installing the new sensor cap, store the sensor in either water or in
the water-saturated air storage chamber.
NOTE: Be sure to update the ODO Sensor Cap Coefficients after
replacement.

12
Maintenance and Storage
Updating the ODO Sensor Cap Coefficients
After installing a new sensor cap, locate the Calibration Code Label on the ODO Sensor Cap Instruction Sheet. This contains the
calibration codes for this particular sensor cap. The value o feach cap coefficient (K1 through KC) can be written with the appropriate
Modbus command (see Modbus Configuration and Commands for more details).
If errors are made in entering the Sensor Cap Coefficients, the instrument will block the update and an error message will appear on
the display. If you see this error message, re-enter the coefficients and check them carefully.
NOTE: After entering the sensor cap coefficients, the ODO sensor must be calibrated.

13
Modbus Configuration & Commands
5.1
5. Modbus Configuration & Commands
Modbus Serial Configuration
ODO RTU operates over RS485. The serial configuration can be modified, including the baud rate, parity, and Modbus slave
address. By default, the baud rate is 9600, slave address is 0x01, and parity is even. As per the Modbus serial specification, there is
one stop bit when parity is set, and two stop bits when there is no parity. All values are big-endian byte ordered.
Slave Addresses
The slave address is set using a single register write command (function code 0x06) of address 0x0000. Addresses in range of 1 to
247 are supported. Devices will allow broadcast write access using address 0x255. The default address is 0x01.
The slave address can also be read using a read holding registers command (function code 0x03) of address 0x0000
Request
Function Code 1 byte 0x06
Register Address 2 bytes 0x0000
Register Value 2 bytes 0x0001
Request
Function Code 1 byte 0x03
Register Address 2 bytes 0x0000
Number Registers 2 bytes 0x0001
Response
Function Code 1 byte 0x06
Register Address 2 bytes 0x0000
Register Value 2 bytes 0x0001
Response
Function Code 1 byte 0x03
Byte Count 1 byte 0x02
Register Value 2 bytes 0x0001
Error
Error Code 1 byte 0x86
Exception Code 1 bytes 0x03 (Illegal Data Value)

14
Baud Rate and Parity
The baud rate and parity is set simultaneously using a single register write command (function code 0x06) of address 0x0001. The
upper byte defines the parity, and the lower byte defines the baud rate from a list of standards.
Parity
None 0x00
Odd 0x01
Even 0x02
Baud Rate
9600 0x00
19200 0x01
38400 0x02
57600 0x03
115200 0x04
Request
Function Code 1 byte 0x06
Register Address 2 bytes 0x0001
Register Value 2 bytes 0x0200
Request
Function Code 1 byte 0x03
Register Address 2 bytes 0x0001
Register Value 2 bytes 0x0001
Response
Function Code 1 byte 0x06
Register Address 2 bytes 0x0001
Register Value 2 bytes 0x0200
Response
Function Code 1 byte 0x03
Register Address 2 bytes 0x0002
Register Value 2 bytes 0x0200
Error
Error Code 1 byte 0x86
Exception Code 1 bytes 0x03 (Illegal Data Value)
The serial configuration can also be read using a read holding registers command (function code 0x03) of address 0x0000.
Modbus Configuration & Commands

15
5.2 Device Information
Device information is available as read-only using a read holding registers command (function code 0x03) starting at address
0x1000. It will identify the product, firmware, and hardware versions. Values can be read as a subset or in a complete block. The
submodel is especially useful, as it indicates whether or not conductivity values are available. The manufacturing serial number is 9
characters long, with the last byte padded by a NULL character.
Address Description R/W Type Default
0x1000 Product [1:0] R U16 0x0003
0x1001 Model [1:0] R U16 0x0001
0x1002 Submodel [1:0] R U16 0x0001 (CT)
0x0002 (T)
0x1003 Firmware Major Revision [1:0] R U16 N/A
0x1004 Firmware Minor Revision [1:0] R U16 N/A
0x1005 Firmware Subminor Revision [1:0] R U16 N/A
0x1006 Hardware Major Revision [1:0] R U16 N/A
0x1007 Hardware Minor Revision [1:0] R U16 N/A
0x1008
Manufacturing Serial Number [0:8] + pad R ASCII N/A
0x1009
0x100A
0x100B
0x100C
0x100D
Printed Circuit Board Serial Number [0:7] R ASCII N/A
0x100E
0x100F
0x1010
Modbus Configuration & Commands
Request
Function Code 1 byte 0x03
Register Address 2 bytes 0x1000
Number Registers 2 bytes 0x0008
Response
Function Code 1 byte 0x03
Byte Count 1 byte 0x10
Register Values 16 bytes Product
Model
Submodel
Firmware Major Revision
Firmware Minor Revision
Firmware Subminor Revision
Hardware Major Revision
Hardware Minor Revision

16
5.3 Data
Values for available parameters are available by via a read input registers command (function code 0x04). Most of these values are
32-bit IEEE-754 floating point numbers in big endian format. Each value is a combination of two registers. The read must read an
entire value, so the read must start at an even (or zero) register address, and read an even number of registers. Any values that are
not available, such as conductivity measurements in an ODO/T device or reserved space will return a NaN (0xFFFFFFFF)..
Address Description R/W Type
0x0000
ODO Saturation (%) [3:0] R Float
0x0001
0x0002
ODO (mg/L) [3:0] R Float
0x0003
0x0004
ODO Local Barometer Compensated (%) [3:0] R Float
0x0005
0x0006
Temperature (C) [3:0] R Float
0x0007
0x0008
Reference Temperature (C) [3:0] R Float
0x0009
0x000A
Time Since Boot (ms) [3:0] R U32
0x000B
0x000C
*Conductivity (us/cm) [3:0] R Float
0x000D
0x000E
*Specific Conductivity (us/cm) [3:0] R Float
0x000F
0x0010
*Salinity (ppt) [3:0] R Float
0x0011
0x0012
*Conductivity nLF (us/cm) [3:0] R Float
0x0013
0x0014
*Total Dissolved Solids (mg/L) [3:0] R Float
0x0015
0x0016
Reserved [3:0] R Float
0x0017
0x0018
Reserved [3:0] R Float
0x0019
0x001A
Reserved [3:0] R Float
0x001B
0x001C
Reserved [3:0] R Float
0x001D
0x001E
Reserved [3:0] R Float
0x001F
*Only available in ODO/CT devices
Modbus Configuration & Commands

17
Request
Function Code 1 byte 0x04
Register Address 2 bytes 0x0000
Number Registers 2 bytes 0x0020
Error
Error Code 1 byte 0x84
Exception Code 1 bytes 0x02 (Illegal Address)
Response
Function Code 1 byte 0x04
Byte Count 1 byte 0x40
Register Values 64 bytes ODO Saturation (%) [3:0]
ODO (mg/L) [3:0]
ODO Local Barometer Compensated (%) [3:0]
Temperature (C) [3:0]
Ref Temperature (C) [3:0]
Time Since Boot (ms) [3:0]
Conductivity (us/cm) [3:0]
Specific Conductivity (us/cm) [3:0]
Salinity (ppt) [3:0]
Conductivity nLF (us/cm) [3:0]
Total Dissolved Solids (mg/L) [3:0]
Reserved [3:0]
Reserved [3:0]
Reserved [3:0]
Reserved [3:0]
Reserved [3:0]
Reserved [3:0]
Modbus Configuration & Commands

18
5.4 Calibration
Assuming the same standard, calibration commands may be sent as a broadcast message to calibrate every sensor on the network.
ODO
It is imperative to keep the ODO user calibration up to date as well as entering new coefficients when the cap is replaced. These
values are supplied with replacement caps.
Factory Reset
ODO values can be reset to the factory calibration by issuing a write single register command (function code 0x06) at address
0x0200 with a value of 0x0001.
Last Calibration Time and QC Score
The time of the last ODO calibration and QC score can be queried to help track internal processes for keeping the devices properly
calibrated. The last time must be maintained during calibrations by the user. These registers do not support writes, as the time
is written in each calibration command. This is only intended to be read. Last calibration time is a 32-bit (two register) value, and
is recommended to be set as epoch time. The last calibration time and QC score are available as read-only using a read holding
registers command (function code 0x03) starting at address 0x0210.
Request
Function Code 1 byte 0x06
Register Address 2 bytes 0x0200
Register Value 2 bytes 0x0001
Request
Function Code 1 byte 0x03
Register Address 2 bytes 0x0210
Number Registers 2 bytes 0x0003
QC Score
Best 0x00
OK 0x01
Bad 0x02
Address Description R/W Type Default
0x0210
ODO Last Calibration Time (s) [3:0] R U32 N/A
0x0211
0x0212 ODO QC Score R U16 N/A
Modbus Configuration & Commands

19
Response
Function Code 1 byte 0x03
Byte Count 1 byte 0x06
Register Values 6 bytes ODO Last Calibration Time (s) [3:0]
ODO QC Score
Zero Calibration
ODO zero point calibration is accomplished by writing an entire block of values (non-divisible) using a write multiple registers
command (function code 0x10). Last calibration time can subsequently be read to verify.
Percent Saturation Calibration
ODO percent saturation calibration is accomplished by writing an entire block of values (non-divisible) using a write multiple
registers command (function code 0x10). Last calibration time can subsequently be read to verify. This calibration is done in 100%
saturated water. Barometric pressure is required to perform the calibration.
Request
Function Code 1 byte 0x10
Register Address 2 bytes 0x0220
Number Registers 2 bytes 0x0002
Byte Count 1 byte 0x04
Register Values 4 bytes ODO Zero Calibration Time (s) [3:0]
Request
Function Code 1 byte 0x10
Register Address 2 bytes 0x0230
Number Registers 2 bytes 0x0004
Byte Count 1 byte 0x08
Register Values 8 bytes ODO % Calibration Time (s) [3:0]
ODO % Calibration Barometer (mmHg) [3:0]
Address Description R/W Type Default
0x0220
ODO Zero Calibration Time (s) [3:0] W U32 N/A
0x0221
Address Description R/W Type Default
0x0230
ODO % Calibration Time (s) [3:0] W U32 N/A
0x0231
0x0232
ODO % Calibration Barometer (mmHg) [3:0] W Float N/A
0x0233
Modbus Configuration & Commands

20
mg/L Calibration
ODO mg/L calibration is accomplished by writing an entire block of values (non-divisible) using a write multiple registers
command (function code 0x10). Last calibration time can subsequently be read to verify. Salinity values are required for ODO
mg/L calibration. If conductivity values are available (ODO/CT), the user-provided salinity value will be overridden with the internal
salinity calculation. The user may just set this value to zero.
Request
Function Code 1 byte 0x10
Register Address 2 bytes 0x0240
Number Registers 2 bytes 0x0006
Byte Count 1 byte 0x0C
Register Values 12 bytes ODO mg/L Calibration Time (s) [3:0]
ODO mg/L Calibration Value [3:0]
ODO mg/L Calibration Salinity (ppt) [3:0]
Address Description R/W Type Default
0x0240
ODO mg/L Calibration Time (s) [3:0] W U32 N/A
0x0241
0x0242
ODO mg/L Calibration Value (mg/L) [3:0] W Float N/A
0x0243
0x0244
ODO mg/L Calibration Salinity (ppt) [3:0] W Float N/A
0x0245
Modbus Configuration & Commands