Hanna Instruments HI 504901, Instruction Manual, Page: 7 / 35

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from 5 to 30 V is applied or when it is disconnected.
This input can come from a relay contact or from an open
collector output (for example from a PLC).
Connect the positive pole of an external power supply to the
positive DIG-IN terminal; connect a command relay between
the negative pole of the external power supply and the nega-
tive DIG-IN (see also below diagram).
Note
Never connect mains or AC voltage supply directly to the
DIG-IN terminal.
Note
The digital input is optoisolated.
DISABLE SMS (DISABLE)
This input works as a digital input (see previous subsection)
and allows to ignore active errors and suspend SMS sending
during operations as calibration, start-up, maintenance, etc.
DIGITAL OUTPUT (DIG OUT)
This optoisolated terminal is an open collector output, which
can be used for external signaling through LED indicators or
small relays (see below diagram).
RS485 SERIAL PORT
HI504901 is also provided with a 2-pin RS485 terminal for
communication with Hanna HI23 , HI24 , HI700 , HI710 ,
HI504 meters series and HI504910 digital transmitter.
The RS485 standard is a digital transmission method that
allows long line connections. Its current loop system makes
this standard suitable for data transmission in noisy environ-
ments.
INSTALLATION
RS232 AUXILIARY PORT
HI504901 is provided with an auxiliary RS232 port (D-Sub
9-pole female plug) for connection to a local PC using an
HI920010 Hanna cable.
Note
Use this RS232 auxiliary port only for local configuration of
the interface with HI504901SW software or local communi-
cation session with an instrument connected to the HI504901
interface (see “Interface Configuration” and “PC Communi-
cation” sections for details).
Note
If the HI920010 Hanna cable is too short for your applica-
tion, please refer to “Appendix” for details about making a
longer communication cable.
RS232 #1 AND RS232 #2 SERIAL PORT
HI504901 is provided with two serial ports (channel #1
and channel #2) for communication with Hanna HI8001
and HI8002 controllers.
Each port is a 3-pin terminal: TX, RX and GND.
To connect the
HI504901 interface to HI8001 or HI8002
controllers, use 9-pin D-Sub connector and shielded cable,
and follow the below indications.
HI8001/HI8002 HI504901
9-pin D-Sub male connector RS232-# terminal
Pin 2 TX
Pin 3 RX
Pin 5 GND
Note
The RS232 standard allows to connect only one instrument to
each serial port.
DIGITAL INPUT (DIG IN)
HI504901 is provided with a digital input, which can be
configured with HI504901SW software (see “Interface Con-
figuration” section) to send an alarm SMS when a DC voltage