40
TWITE INSTRUMENTS
THERMOSTAT MODEL TD-196 OPERATING MANUAL
PRINTER COMMUNICATIONS
Up to 16 units
(TD-196)
can be connected to a printer for printing out
of temperatures at preset times, data logged temperatures and parameter set points.
All units in the chain must have their RS485 - terminals connected
together
(in parallel)
and their RS485 + terminals connected together
(in parallel)
using single twisted pair coaxial cable. The shield must be connected to GROUND at
one end only
(not at each unit).
To connect to a printer with an RS232 port, the TD-196's + serial
output must be connected to the rs232 receive input
(pin 3 on the 25 pin D connec-
tor)
and the ground output/input on the TD-196 connected to the signal ground of the
printer
(pin 7 on the 25 pin D connector).
The pins 4 & 5 on the 25 pin D connector
must be tied
(shorted)
together. This type of communication is only available if all
TD-196 units are in close proximity to each other and the printer,
(no more than 6
metres).
When using the Remote Display Module the distance may be extended
to 500 metres between all units and the Remote Display unit. The printer is con-
nected to the remote display unit via a standard parallel printer cable, and does not
require RS232 interface. For more information on the Remote Display Module, see
REMOTE DISPLAY.
All units must be set to have a unique identity number
(1 - 16 inclu-
sive)
. As each unit prints its temperature
(at preset times)
it places its data in its
relative position
(compared to its unit number)
on the line of an A4 page. The unit
that is set to do a LINE FEED also prints the current time at the start of the line
before it prints its temperature on its relevant position then sends a line feed to allow
the next lot of temperatures to print at the next time. The unit that has the largest
number
(unit identity)
should be set to send the line feed, as the unit number deter-
mines the time when the unit is allowed to print after the RS485 line becomes
available.
When printing parameter set points, data logged or maximum and
minimum
(see PRINT)
the unit will send a line feed and a carriage return then its
own identity number plus time and date before it sends its data.
If the 8 channel option is installed on any unit in the chain, these units
will always send a line feed and its identity number if more than one sensor
(or one
sensor other than channel one)
temperature is to be sent.
The unit that sends the line feed also counts line feeds as they are sent
to the printer and will send a form feed after 56 line feeds have been sent to the
printer. Then this unit will send a heading with channel numbers etc. for the begin-
ning of a new page. See Setting
LINE FEED YES/NO
for more information on
page breaks and headings also.
