In-Situ RDO PRO Process Optical Dissolved Oxygen Sensor Manual - Manual (Page 16)

5.5.2 Power Connections
The red wire provides power for all system modes. Analog output is disabled by default. However,
the 4-20 mA current loop output can be continuous in Modbus or SDI-12 mode as long as Modbus
device register 9507 is set to 1.
5.5.3 Communications
The device automatically switches between Modbus and SDI-12 modes depending on which of the
two interfaces has activity. Modbus and SDI-12 cannot be used at the same time—whichever one is
currently in use will block communication on the other.
5.5.4 Additional Information
For additional information on Modbus and SDI-12 communications, including the SDI-12 commands
and Modbus registers, see the In-Situ Modbus Communication Protocol technical note, available at
www.in-situ.com.
6.0 Modbus Registers
6.1 Common Registers
Register Size
(registers)
Mode & Access Level
(R/W)
Data
Type
Description
9001 1 R/W ushort Device Id (Device Id = 12 for RDO PRO)
9002 2 R/W ulong Device Serial Number
9004 3 R/W time Manufacture Date
6.2 Sensor Status Registers
Register Size
(registers)
Mode & Access Level
(R/W)
Data
Type
Description
0005 3 R1 time RDO cap start time, 0 = no cap
0008 3 R1 time RDO cap exp. time, 0 = no cap
6.3 Device Specific Measurement Registers
Register Size
(registers)
Mode & Access Level
(R/W)
Data
Type
Description
Dissolved Oxygen Concentration
0038 2 R1 float Measured value, C
0
0040 1 R1 ushort Parameter Id = 20
0041 1 R1/W2 ushort Units Id
117 = mg/L (default)
118 = µg/L
0042 1 R1 ushort Data Quality Id
0043 2 R1/W3 float Off line sentinel value (default = 0.0)
0045 1 R1 16 bits Available Units = 0x0030 (48)
Temperature
0046 2 R1 float Measured value
0048 1 R1 ushort Parameter Id = 1
Page 16 Modbus Registers