YOKOGAWA DO71 User manual

Technical Optical Dissolved Oxygen, model DO71/DO72
Information MODBUS Communication
TI 12J06J01-00EN-P
Yokogawa Process Analyzers Europe B.V. TI 12J06J01-00EN-P, 1st Edition
Euroweg 2, 3825 HD Amersfoort, The Netherlands Copyright © 2022
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MODBUS Communication - Contents 3
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Contents
Introduction....................................................................................................................................4
1. General ....................................................................................................................................5
1.1 MODBUS setup ...............................................................................................................5
1.2 Function code / Exception code ...................................................................................5
1.3 MODBUS communication..............................................................................................6
1.4 Connection......................................................................................................................6
2. MODBUS map.........................................................................................................................8
2.1 Hold Register DO............................................................................................................9
3. Failures and Warnings DO..................................................................................................17
4. Low/High Point Calibration DO...........................................................................................18
5. Revision History...................................................................................................................19

MODBUS Communication - Introduction 4
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Introduction
This document describes MODBUS communicationby the Optical Dissolved Oxygen (DO) sensor,
model DO71 and DO72, for a basic user.
Before communication using the MODBUS protocol, refer to the User’s Manual of the Optical
Dissolved Oxygen sensors, model DO71 and model DO72 (IM 12J06J01-00EN-P) for details of
the parameters and connections.
Latest revision of the User’s Manual can be downloaded from the website:
https://www.yokogawa.com/solutions/products-platforms/process-analyzers/liquid-
analyzers/#Downloads
You can use the QR-code for quick-access.
NOTE
No part of the Technical Information may be transferred or reproduced without prior written
consent from YOKOGAWA.
YOKOGAWA reserves the right to make improvements in the Technical Information and product
at any time, without notice or obligation.

MODBUS Communication –General 5
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1. General
Optical Dissolved Oxygen sensors are slave devices which can be configured or are sending
process data using Bi-directional digital communication (RS485, half-duplex) with full MODBUS
(RTU) support. The power for the Optical Dissolved Oxygen sensors must be supplied by a HOST
or by a separate power supply in the range +7VDC up to +30VDC. Maximum power of the Optical
Dissolved Oxygen sensors is 1W in active mode, and 150mW in stand-by mode.
1.1 MODBUS setup
The following list shows the required setting by HOST to establish communication between the
HOST as master device and the Optical Dissolved Oxygen sensor as slave device. The procedure
for changing list items is explained in the following chapters in this document.
Slave address : 1
Serial Profile : 19200 bps, 8 data bits, No parity, 2 stop bits
NOTE
Slave address and Serial Profile are configurable as explained in this document.
IncaseofusingmultipleOpticalDissolvedOxygensensorsinabussystem,connectedtooneHOST,
the Slave addresses of all the Optical Dissolved Oxygen sensors must be unique. Because initial
settingofaddressis1itisrecommendedtochangetheinitial addressvaluetopreventcommunication
conflicts in case a new purchased Optical Dissolved Oxygen sensor is added to the bus.
Serial profile of the slave device(s) mustbe the same as the HOST.
1.2 Function code / Exception code
MODBUS Function codes used for DO71 and DO72:
Function
Function code (hex)
Read Hold Register
03
Write Single Register
06
Write Multiple Registers
10
Exception codes used for DO71 and DO72:
Name
Exception code
Meaning
Illegal Function
0x01
The Function code received is not an
allowable action for the slave
Illegal Data Address
0x02
The Data Address received is not an
allowable address for the slave

MODBUS Communication –General 6
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1.3 MODBUS communication
If the Optical Dissolved Oxygen sensor is used with a HOST, the following must be considered.
⚫MODBUS response timing
TheOpticalDissolvedOxygensensor’s HR (HOLDRegister)responsetoaHOSTHR Readrequest
is within 100ms. The timing in between a response and a new request must be at least 10ms.
Figure 1.3: Timing diagram
⚫HOLD Register renewal cycle
Process value sent in HOLD Register is configurable, initial value is 1 s.
1.4 Connection
⚫BUS system
Wired connection:
Figure 1.4: DO71 sensor with HOST
< 100 ms > 10 ms
HOST HR: Hold Register
DO sensor
HR Request
HR Response
HR Request

MODBUS Communication –General 7
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Table 1.4.1: DO71 connection definition
Terminal
pin no.
(Fixed cable)
Wire
colour
Description
12
yellow
RS485 Data + (B)
11
green
RS484 Data –(A)
13
white
Power - GND
10
brown
Power - VDC
14
transparent
Cable shield / Probe body
Table 1.4.2: DO72 connection definition
Terminal
pin no.
(WU10-V-D-xx)
Wire
colour
Connector pin
(Variopin)
Description
12
green
H
RS485 Data + (B)
11
yellow
G
RS484 Data –(A)
13
white-shield
D
Power - GND
10
white-core
C
Power - VDC
14
black
Shield
Cable shield /
Probe body
xx: Cable length in meters

MODBUS Communication –MODBUS map 8
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2. MODBUS map
Data type for Optical Dissolved Oxygen sensor MODBUS map:
Data type
Definition
Float
floating point (4byte, little endian byte swap [CDAB])
IEEE754
NaN: 0x7FFFFFFF
Uint32
32 bit unsigned integer, little endian byte swap [CDAB]
ASCII
character set (using one byte per character), multiple registration possible,
little endian byte swap [CDAB])
Access (load/import) to multiple data types, such as Float, Uint32, ASCII etc., must be
implemented at once. The current version does not support Script yet.
Access
Function
Function Code (hex)
Data Access
16 bits
Read Hold Registers
03
Write Single Register
06
Write Multiple Register
10
Hold Registers are Read only (R) or Read/Write (R/W).
NOTE
The content of this Modbus Map is based upon DO71 firmware YPA 1.4.0.xx and DO72 firmware
YPA 1.4.0.xx

MODBUS Communication –Hold Register DO 9
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2.1 Hold Register DO
If applicable, in the Value/description field the Factory Default setting (D), Low limit setting (L) and
High limit setting (H) are explained. NaN does mean that there is Not a Number defined.
NOTE
Because no limit checks are implemented, incorrect settings or settings outside the specified range
are accepted as is. Pleasetake care that settings aredone correctly and within the specified range.
Address
Item name
Data type
Access
Value / description
1031
Firmware version
ASCII
R
Alphanumeric Firmware version code:
16 bytes, 8 addresses
2089
Oxygen unit
Uint32
R/W
0x 0000 0010 % vol O2
0x 0000 0020 % air saturation
0x 0000 0040 ppb (µg/L) 2)
0x 0000 0080 ppm (mg/L) 2)
0x 0400 0000 µmol/L 2)
0x 0800 0000 % DO saturation
0x 2000 0000 hPa (mbar)
0x 4000 0000 ppm gas 1) 2)
0x 8000 0000 Torr
Remark:
1) ppm gas only possible with DO72-T
2) Setting not possible in
measurement mode “Dry”
(register HR5703)
D: % DO saturation
2091
Oxygen value
Float
R
Calculated oxygen value in oxygen unit
as defined in register HR2089
Remark:
1) The calculated oxygen value is only
updated if an interval rate is set
(register HR3499)
2) When value is -999 this means
there is no calculated output
2093
Error
Uint32
R
For details see Section 3.1
2409
Temperature Unit
Uint32
R/W
0x 0000 0002 K
0x 0000 0004 °C
0x 0000 0008 °F
D: °C
2411
Temperature Value
Float
R
Measured temperature value used for
temperature compensation

MODBUS Communication –Hold Register DO 10
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Address
Item name
Data type
Access
Value / description
3115
Salinity
Float
R/W
Salinity value used for salinity
compensation (unit is g/L)
D: 0
3145
Pressure Comp. Unit
Uint32
R
0x 0080 0000 hPa (mbar)
Remark:
1) This is a fixed unit
D: hPa (mbar)
3147
Volatile Pressure Comp. Value
Float
R/W
Pressure value in hPa (mbar) used for
oxygen calculation
Remark:
1) If included in a multi register write,
no change will take place
2) Value is not written into Flash
memory
D: By default, this is the Persistent
Pressure Comp. value (register
HR3153)
3153
Persistent Pressure Comp. Value
Float
R/W
Default setting for compensation
pressure value in hPa (mbar)
Remark:
1) Do not use this register frequently
due to limited number of write
cycles into Flash memory. For
frequent pressure changes please
use register HR3147
2) Value is stored into Flash memory
and restored at startup
D: Set by manual input
3497
Interval Unit
Uint32
R/W
0x 0000 0001 seconds
Remark:
1) This is the time unit for the oxygen
measurement interval rate, fixed
set to seconds
D: seconds
3499
Interval rate
Uint32
R/W
Oxygen measurement interval rate in
time unit as set in register HR3497
Remark:
1) Setting the interval rate to 0
deactivates the continuous
measurement
(see register HR9000)
D: 1
L: 0
H: 300