Communication; Pc Communication - Hanna Instruments HI 720 Instruction Manual

COMMUNICATION

For remote interaction with your controller, enter the setup mode, confirm the
"Communication" menu, and select the "Connection type" from among 4 avail-
able options:
• PC
• HI 504900 GSM module
• HI 504901 GSM supervisor
• HI 504902 Modem
PC C
OMMUNICATION
Choose the "PC" connection type to communicate
with the controller from your PC, through an RS485
network and the HI 92500 Windows
software.
RS485 standard is a digital transmission method that allows long lines connec-
tions. Its current-loop system makes this standard suitable for data transmission
in noisy environments.
The user-friendly HI 92500 offers a variety of features such as logging selected
variables or plotting the recorded data. It also has an on-line help feature to
support you throughout all operations.
The readings logged into the HI 720 internal memory can be downloaded through
HI 92500, which makes it possible for you to use the powerful means of the
most diffused spreadsheet programs.
Simply run your favorite spreadsheet program, open the file downloaded through
HI 92500, and you will be able to elaborate the data with your software (e.g.
graphics, statistical analysis).
To install HI 92500 you need just a few minutes to follow the instructions printed
on the disk's label.
Specifications
The RS485 standard is implemented in the HI 720 series with the following
characteristics:
• Data rate: up to 19200 bps (manually selected)
• Communication: Bidirectional Half-Duplex
• Line length: up to 1.2 km typ. with 24 AWG cable
• Loads: up to 32 typ.
• Internal termination: none
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® compatible
Connections
The connections for the 6-pin RS485 terminal provided are as follows:
There is an internal short between the two A pins and between the two B pins.
The instrument has no internal line termination. To terminate the line, an external
resistor equal to the characteristic line impedance (typically 120 ) must be added
at both ends of the line.
The RS485 can connect up to 31 controllers on the same physical network. All
the units are slave devices and are monitored and controlled by a single master
station (typically an industrial PLC or PC).
Each HI 720 unit is identified by its Process ID number (00 to 99), which corre-
sponds to the Process ID configured through the setup item G.11.
(If the instrument does not recognize the address within the command string,
then it discards all the following bytes).
As additional feature, the controller is also provided with two pins
(5V and GND) in order to apply the Fail Safe Open Line protection
method. To avoid erroneous readings in Open-Line conditions,
pull-up and pull-down resistors should be connected as shown.
The Fail-Safe resistors are connected only to one unit in the line,
and their value depends on the application and characteristic im-
pedance of the connection cable.
The GND pin of the interface connector and all the interface signals are
optoisolated from instrument ground, probe and temperature sensor.
Before connecting the meter to the computer, consult the computer manual.
The process controller can only work as a slave component. In other words it
can work as a remote terminal equipment answering to the commands only.
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