YSI IQ SensorNet MIQ/A-MOD Module - Manual (Page 25)

MIQ/(A-)MOD Data transmission
25 ba76021e01 01/2012
4 Data transmission
4.1 Overview
Data transmission is carried out via the RS 485 interface with the
Modbus RTU protocol.
The following sensor data is transmitted:
 Sensor number (Sxx)
 Sensor status
 Sensor model
 Status info of sensors
 Measuring mode
 Measured value status (main and secondary measured value)
 Main measured value
 Secondary measured value
Note
The transmitted data of all IQ S
ENSOR N ET sensors is given in the YSI
document, "IQ S ENSOR N ET sensors: encoded data for field bus
communication" (ba76073e). It is permanently updated when new
sensors are available and when the sensor software is modified (if the
modifications are relevant for the transmitted sensor data). The latest
version is available on the Internet, in the download area for operating
manuals. Use the search function for the download and search for
"ba76073e".
4.2 Modbus query
With each query of sensor data via the Modbus protocol, a block of
consecutive registers is read (up to all of the 240 registers).
For a query of sensor data, determine the first register and the number
of registers to be read (1 ... 240).
Determining the first
register to be read
The first register to be read depends on the sensor number (Sxx) [1 ...
30] and the number of the sensor register (R) [1 ... 8]:
[(Sxx - 1)] * 8 + R.
Example: Determine the first register with data for the sensor S10:
[(10 - 1) * 8] + 1 = 73