Anyone faced with the task of monitoring and controlling analogue and digital signals distributed around a site will be very interested in a neat new system from ComputerBoards. The CB 7000 family is a set of individual microprocessor controlled modules designed for different types of sensors, which communicate over a simple two-wire RS-485 link. This network simply connects into any PC serial port through an RS-485 to RS-232 converter, giving monitoring and control of up to 2048 points under Windows or even DOS.
     There are CB 7000 modules for thermocouples and RTDs as well as standard voltage and 4-20mA inputs. The temperature measurement modules automatically handle Cold Junction Compensation! And beneath the system's apparent simplicity lies some advanced technology, including a 16-bit Sigma-Delta A/D converter in the analogue input modules, and a programmable slew rate in the CB-7017 analogue output module which allows voltage changes to be controlled within limits.
     The CB 7000 approach can offer serious cost savings in applications which would normally require expensive isolation modules. This is thanks to an inherent 3000V isolation between the network and the PC. This not only protects the PC, but increases data reliability by eliminating ground loop and common mode problems.
     We perhaps shouldn't be surprised (this is a ComputerBoards system after all) but the setup, diagnostic and applications software comes free with the system. For a nominal additional price, there's also a Windows DLL which can be called from most languages, and a DDE server which allows hot-linking to many other programs. The basic software offers everything you need to start with: initialise RS-232, open/close COM ports, send/receive commands and search for modules on the network. We think it'll play a major part in the undoubted success which the CB 7000 system is bound to have.

Mick Halnan