Direct Read Modbus/Sdi-12; Reading Via Modbus Rtu - Seametrics CT2X Instructions For Use Manual

DIRECT READ MODBUS & SDI - 12
Reading Via Modbus RTU
®
Setting Baud Rate
Your CT2X comes configured to communicate at 38,400
baud, with 8 data bits, one stop bit, and no parity. The
sensor can also be set to 19,200 or 9600 baud, if needed for
your application. You must use Aqua4Plus 2.0, see Settings,
to make baud rate changes.
Taking Measurements
Reading Registers
Read measurements using Modbus function 03 – Read
Holding Registers. Readings are located in two registers
each, starting at address 62592. (CT2X register addressing
is zero based, i.e., starts at zero. If your equipment uses one
based addressing, you will need to add one to the register
addresses.)
Register Addresses for the CT2X
Temperature
Conductivity (Linear)
Conductivity (nLFn)
Pressure
Salinity*
TDS*
*Firmware version 2.7 or higher
Measurement Timing
When you request a reading via Modbus, the sensor wakes
up, returns the current values in the registers, and then
starts taking new readings and updating the registers. After
approximately 10 seconds, if no more readings have been
requested, the sensor goes back to sleep.
Because of this, the first reading you get will be old. If you
are taking readings at intervals of less than 10 seconds,
simply ignore the first reading — all remaining readings will
be current. On the other hand, if you are taking readings
at intervals of greater than 10 seconds, take a reading,
ignore it, wait one second, take another reading. Record
this second reading.
Seametrics • 253.872.0284
Zero based One based
62592 62593
62594 62595
62596 62597
62598 62599
62600 62601
62602 62603
Data Format
The data is returned as 32-bit IEEE floating-point values,
highword first, also referred to as big-endian or float
inverse.
For further information and detailed Modbus examples,
see Seametrics' Technical Bulletin available from our web
site (www.seametrics.com/downloads).
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CT2X INSTRUCTIONS
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