Specifications

45
5.4 CALCOMMS - Computer Interface
CALCOMMS is a graphic Windows™ based software package designed for PC
supervision of CAL 3300 Controllers. It offers the capability of remote adjustment,
instrument configuration, cloning, saving and retrieving instrument settings to files
together with logging and charting in real time. Communications uses the MODBUS®
protocol via a fully isolated RS485 link.
To gain full benefit of CALCOMMS software, it is recommended that the PC is fitted with
a Pentium processor (although a 486 will work) and is running WINDOWS 95 or
Windows NT programs. A minimum of 16 MB RAM is recommended to run the program
(slightly less is OK), together with enough free hard disc space to meet logging
requirements.
Because the controllers are “stand alone” they do not need PC supervision for their
normal function, and will continue to control the process unaffected by failure of any part
of the communications loop.
When used with the Model 518 Chamber, the Temperature & Humidity Microprocessor
COMM PORTS are wired together, in parallel. One RS-485 COMM PORT, common to
both controllers, is located on the Side Interface Panel.
5.4.1 Set-up and Installation
(See Pp. 2 & 3 in the CALCOMMS Manual)
5.4.1.1 RS 485 COMM PORT
RS-485 is a half duplex serial communications link and is the standard
most commonly used for industrial applications due to it’s high noise
immunity and multi-drop capability. It enables a PC to communicate with
up to 32 instruments over distances of over 1200 meters, and requires
the addition of an RS-485 interface card, or a separate RS-232/485
converter.
The RS-485 COMM PORT is a 9-pin subminiature-D female connector
located on the ‘Side Interface Panel’.
5.4.1.2 RS-232/485 Converter
The RS-232/485 Converter will not be needed if the computer is outfitted
with an RS-485 interface card.
The converter is a 9-pin / 9-pin in-line style connector. The converter is
gray and bears the label ‘ RS-232 TO RS-485 / Model 485SDD9R’.