Direct Read Modbus/Sdi-12; Power Consideration; Reading Via Modbus Rtu - Seametrics TempHion Instructions Manual

DIRECT READ MODBUS & SDI - 12

Power Consideration

If your sensor does not have internal batteries and is not
powered continuously by an auxiliary power supply, then
you must turn power on to the sensor at least two seconds
before a reading is to be taken to allow the sensor to warm
up.
Reading Via Modbus RTU
®
Setting Baud Rate
Your TempHion 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 to
make baud rate changes.
If needed, set your TempHion to the desired baud rate in
user settings.
Taking Measurements
Reading Registers
Read measurements using Modbus function 03 – Read
Holding Registers. Readings are located in two registers
each, starting at address 62592. (TempHion 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 with Firmware 2.5 or higher
Temperature
pH (in pH units)
ISE (in ppm)
ORP (in Eh)
pH (in mV)
ISE (in mV)
ORP (in mV)
Register Addresses with Firmware prior to 2.5
Temperature
pH (in mV)
ISE (in mV)
ORP (in mV)
pH (in pH units)
ISE (in ppm)
ORP (in Eh)
Seametrics • 253.872.0284
Zero based One based
62592 62593
62594 62595
62596 62597
62598 62599
62600 62601
62602 62603
62604 62605
Zero based One based
62592 62593
62594 62595
62596 62597
62598 62599
62600 62601
62602 62603
62604 62605
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.
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 application note, available on our website
at www.seametrics.com.
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TEMPHION INSTRUCTIONS
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