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RS485 COMMUNICATION
The digital transmission of measurements, error and status
information is implemented through an RS485 link.
The transmission can be directed to an HI 504 or to a com-
puter workstation, which can be connected locally or remotely
through a modem connection.
RS485 standard is a digital transmission method that allows
long lines connections. Its current-loop system makes this
standard suitable for data transmission in noisy environments.
Data transmission from the instrument to the PC is possible with
the HI 92500 Windows
®
compatible application software of-
fered by Hanna Instruments and an RS232 to RS485 adapter
with Send Data Control connected to the serial port of your PC.
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 the op-
eration.
The readings logged into the HI 504910 internal memory
can be downloaded through HI 92500.
HI 92500 makes it possible for you to use the powerful means
of the most diffused spreadsheet programs. Simply run your
favorite spreadsheet program and open the file downloaded
by HI 92500. It is then possible to elaborate the data with
your software (e.g. graphics, statistical analysis).
To install HI 92500 you need a 3.5" drive and few minutes to
follow the instructions conveniently printed on the disk’s label.
Contact your Hanna Dealer to request a copy.
SPECIFICATIONS
The RS485 standard is implemented in HI 504910 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 24AWG cable
Loads: up to 32 typ.
Internal termination: none
Only 2400 bps can be used for connection to HI 504.
Windows
®
registered Trademark of “Microsoft Co.”
FAULT CONDITIONS
The below fault conditions may be detected by the software:
• EEPROM data error
• serial communication internal bus failure
• dead loop.
EEPROM data error can be detected through EEPROM test
procedure at start-up or when explicitly requested using setup
menu, or during normal operational mode if a checksum
control fails.
When an EEPROM error is detected during normal mode, a
fault alarm is generated.
To close an error an EEPROM test (see “Selftest procedures”
section) or reset is required.
As soon as an EEPROM error is detected, the scrolling mes-
sage “EEPROM reset needed - Press up button to reset stored
data or right button to ignore” will appear on the primary
LCD.
If the key is pressed, the instrument restarts operation, but
the device will be in Hold mode in any case (i.e. no mea-
surement will be acquired).
If the æ key is pressed, all the data stored in the EEPROM are
erased and the default values loaded. After that, the device
must be completely recalibrated.
An internal bus error is detected when internal transmission
is not acknowledged or a bus fault occurs for more than a
certain number of unsuccessful transmission attempts (due
for example to a damage occurred to one of the ICs con-
nected to the internal bus). After that the controller displays a
sliding message “Serial bus error”.
If the error is due to impossible communication, all the in-
strument tasks are stopped, the red LED blinks and the “Serial
bus error” slides forever (repair can not be postponed).
A software watchdog is provided in order to detect dead loop
conditions or other causes that make the software stuck. If it
happens, a software reset is generated after a time-out of 1
second.
