SERIAL-DATA COMMS ISOLATOR
The MTL5051 provides bi-directional serial data communication from a computer system in safe area to instrumentation in a hazardous area. It is used to provide a fully floating dc supply for, and serial data communications to: MTL643, MTL644, MTL646 and MTL647 IS text displays, other IS instrumentation, keyboards or a mouse. It can also be used for data communications across a hazardous area.
See also common specification Location of field equipment Zone 0, IIC, T4-6 hazardous area Div 1, Group A hazardous location Safe-area signal RS232 or RS422 Hazardous-area signal MTL640 Series mode: To hazardous area: 3V signal superimposed on 12V (nominal) supply From hazardous area: 5mA signal superimposed on quiescent current Across hazardous area communications mode: To hazardous area: 10mA current source From hazardous area: 10mA current source IS RS232/TTL devices mode: To hazardous area: RS232-compatible signal levels From hazardous area: TTL/RS232 signals LED Indicators Green: power indication Max. power dissipation within unit 1.7W at 24V, 25mA load Maximum power consumption (25mA load) At Vs=20V, 105mA At Vs=24V, 90mA At Vs=35V, 70mA Comms bandwidth 643/4 mode 1200 to 9600 baud Other modes up to 19.2 kbaud Safety description Terminals 1,2,3,4 only 14V, 800mW, 192mA Terminals 1,3,4 only 14V, 350mW, 88mA Terminals 1,2,3 only 14V, 450mW, 108mA Terminals 1,5,6 only 15V, 70mW, 35mA Terminals 1,2,5,6 only 20V, 460mW, 139mA Terminals 1,2,3,4,5,6 only 20V, 810mW, 227mA Hazardous area supply terminal 2 +12V mode 12.0V ± 5% (load <23mA) +12V mode 8.0V min (load >23 to <50mA) +5V 5.6V ± 5% (load >23 to <50mA) Hazardous Interfacing See MTL640 Series for details of interfacing with MTL643, MTL644, MTL646 and MTL647 IS text displays. Across hazardous areas communications mode The MTL5051 is used in pairs to transfer bi-directional fullduplex data across hazardous areas, as shown above. Current switching is used to minimise the bandwidth-limiting effects of long cables. Interfacing to an IS keyboard, mouse or other device Communicating with RS232-level interfaces, such as an IS keyboard, mouse, etc. is achieved by using one or more MTL5051 units as required by the device. (TTL level interfaces are also accommodated by the TTL-compatibility feature of RS232 receivers.) The supply to the IS equipment may be selected to be either 5V or 12V by switch on top of unit.