Hanna Instruments HI 21 Series - Manual (Page 15)

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CONNECTIONS
The connections for the 4-pin RS485 terminal provided (#1
on page 7) are as follows:
The instrument has no internal line termination. To terminate
the line, an external resistor equal to the characteristic line
impedance (typically 120
Ω) must be added at both ends of
the line.
Up to 32 units can be connected to the same RS485 line,
with a total line length of up to 1.2 Km using 24AWG cable.
To minimize electromagnetic interferences, use shielded or
twisted pair cable to connect the units.
Each HI 21/HI 22 unit is identified by its process ID number
(setup item “01”).
The HI 21/HI 22 controller acts as a “slave” device: it only
answers to commands received from a “master” device (e.g.
an industrial PC) connected to the line.
RS485 COMMUNICATION
HI 21XY2, HI 21XY3 and HI 22XY2 are provided with an
RS485 port.
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 soft-
ware offered by Hanna Instruments.
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 operation.
HI 92500 makes it possible for you to use the powerful means
of the most diffused spreadsheet programs (Excel
© , Lotus
1-2-3 © etc.). Simply run your favorite spread sheet and open
the file downloaded by HI 92500. It is then possible to elabo-
rate 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 21/HI 22 with the
following characteristics:
Data rate: up to 9600 bps
Communication: Bidirectional Half-Duplex
Line length: up to 1.2 Km typ. with 24AWG cable
Loads: up to 32 typ.
Internal termination: none
Excel © Copyright of “Microsoft Co.”
Lotus 1-2-3 © Copyright of “Lotus Co.”
Windows ® registered Trademark of “Microsoft Co.”