RS 232 converter - current loop is a technical means for the conversion of signals between the voltage RS 232 interface and a 20mA current loop. The interface current loop ensures high resistance to interference and it is suitable especially for industrial environment or for the transfer of data at longer distances. The converter is manufactured in a desktop version and it is technically designed in the way ensuring quality transmission parameters and high functional reliability.
The converter ensures galvanic separation of the two interfaces. It is designed for leading the current loop in the environment with the category of over-voltage of up to 4 kV (according to STN 33 0420). The converter ensures the protection against peak over-voltage above 4 kV (e.g. high over-voltage as a result of lighting). It is suitable to add the current loops for such purposes with over-voltage protection of the respecitive stage (e.g. CERBERUS, DEHN, SELTEKO, HAKEL).
The receiver and the transmitter of the current interface is able to be adjusted separately into the active or passive state (by shifting switches at the bottom of the converter), which allows to adjust the converter to any device with the current loop interface. However, it has to be ensured that in one current circuit only one side is be active (e.g. active transmitter or passive receiver).
Connection of the converter
The converter is connected to the 230 V mains supply by means of a power supply cable, fixed to the converter. The connector of the RS 232 interface (female as standard) is connected to a flexible cable. The interface of the current loop is ended by a fixed connector (D-Sub 9, female) at the back of the converter.
Signalling LEDs
The LEDs on the front panel signal the operational state of the converter:
- PWR (green) – connection to the power supply
- RxD, TxD (red) – state in the circuit of the current loops
If the communication is not in progress, while the RS 232 input 232 is connected, TxD and RxD LEDs must be off (currents travel in both circuits). The on-state of either of them signals that current does not travel in the respective circuit (cut line, both ends of the line are connected as passive, the output TxD on the side of RS 232 is not in high, etc.) During the communication, the TxD and RxD LEDs signal transmission (blinking or permanent on-state) is indicated.
Description of switches
Connection of the RS 232 connector
RTS-CTS and DTR-DSR signals are connected in the D-Sub connector. The rest of the pins of the D-Sub connector are not connected.
Note:
Communication programmes for software communication control (e.g. Norton Commander Link), require inter-connection of RTS-CTS a DTR-DSR (simulated response). Programs that require hardware communication control need to be tested (the communication might not work).
Connection of the current loop:
Example of the connection of two converters:
