Issue
In some applications, a RS-232 to fiber optic converters draws power directly from the host device’s RS-232 pins

Product Line
ION 8650/8600

Environment
RS-232 serial connection on COM1

Resolution
Before we begin let’s define the standard voltage levels that constitute the logical states required for data transmission(TD and RD) as well as the control signal voltages ( RTS/CTS, DTR)

Data transmission Voltages levels (TD or RD)	Logical state
-3 to -25 V	1
+3 to +25 V	0

Control  Signal Voltage levels (RTS/CTS or DTR)	Logical state
-3 to -25 V	OFF
+3 to +25 V	ON

The ION meters act as Data terminal Equipment (DTE) and it can initiate a data transfer by placing the RTS in the ON state.  Some circuits can be powered off the RS-232 using the DTR, RTS and the TD output lines off the ION 8650/8600 meters. The TD pin is typically set to logic 1 when no data is sent and hence it would have a negative voltage most of the time. Moreover, the RTS/DTR will have a positive voltage when operating normally but the user can invert the RTS voltage level using ION setup if needed.

The ION meters use an industrial class RS-232 driver that can provide a standard current output of 10 mA while the output voltage levels at no load are  +/-9 volts. The fiber optic converter needs to be equipped with a voltage regulation circuit that is capable of supplying a regulated voltage to power itself. The RS-232 drive equipped on the ION 8650/8600 meters is designed to supply around 15 mW when connected to an RS-232 circuit (3 kohm resistance) but can potentially supply 40-60 mW . An external power source is necessary if the RS-232 peripheral power requirements are not attained by the meter’s RS-232 drive. The graph  above shows the voltage drop of the ION 8650/8600 RS-232 driver's output line versus the current

Đã phát hành cho: Schneider Electric Việt Nam