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NOTE
REMINDER
Full duplex (point-to-point) connections
NOTE
Half duplex and polled (multi-drop) operations
Commands, queries & responses
Basic protocol
The frequency of temperature sampling for the report (in seconds) can
then be selected from the options on the LCD screen. The report param-
eters range from a report each second (keypad selection [2] [ENTER] )
to a report every two minutes (keypad selection [8] [ENTER] ).
This option may be turned off (selection 1) if there is no computer
connected via the serial line.
The serial connection can only provide time interval reports of the actual
and desired bath temperatures if the CT-2000 is configured in the point-
to-point mode of operation. Otherwise, the REPORTS DISABLED
message will appear on your LCD and you will not be able to access
report configuration options until the point-to-point mode is resumed.
The RS-232 interface is furnished for a direct connection between the
CT-2000 and one computer. A DB-25 connector on the rear panel of the
CT-2000 is configured as Data Communication Equipment (DCE). This
configuration permits a direct connection (straight through cable--pins 1-
8, 20).
An existing computer's DB-9 connector may be used with a DB-25
adaptor cable (DB-25 male connector to DB-9 female connector).
The RS-485 interface is provided to permit network connections from
one computer to a multiple number of instruments. A three-wire (with
feed-through) screw terminal connector is located on the CT-2000 rear
panel. A three-conductor cable (two wire shielded preferred) can be
connected to the instrument via this terminal. The computer must have an
RS-232 to RS-485 adaptor plugged into the computer serial port. With
the 3-wire connection in place, the network is capable of supporting up to
16 instruments at cable distances up to a combined total of 4000 feet.
With three or more occupants or long distances, termination resistors may
be added to enhance the performance of network operations. Contact
CANNON
®
Instrument Company for further assistance on more exten-
sive network configurations.
The protocol for the serial interface includes commands and queries sent
by the master controlling computer and responses sent by the CT-2000 in
reply. The CT-2000 may also issue timed interval reports automatically if
configured to do so in the point-to-point mode (see Reports, previous
page). In the polled (multi-drop) mode, specific reports will only be
issued in response to a specific query.
®
CT-2000 Constant Temperature Bath
CANNON
Revision 1.0g—February, 2012; CANNON
2139 High Tech Road • State College, PA 16803 • USA
®
Instrument Company
23
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