Campbell Scientific SC32B SC32B Optically Isolated RS-232 Interface - Page 9

SC32B Optically Isolated RS-232 Interface 4. Operation Power for the SC32B datalogger section comes from the 5 V supply on pin 1 of the datalogger CS I/O. Communication logic levels to and from the datalogger are referenced to this voltage, ranging from 0 to slightly less than 5 V. Power for the RS-232 section is isolated from the datalogger 5 V supply via a transformer/isolator. An on-board DC to DC converter supplies the negative voltage required for RS-232 signals. When the SC32B first receives a character from the RS-232 peripheral (pin 3), 5 V is applied to the datalogger Ring line (pin 3) until the datalogger Modem Enable (ME) goes high, putting the datalogger into the Telecommunications Mode. The SC32B does not perform baud rate translation. The data speed going out will match the data speed coming in. If you are having trouble communicating, check that the datalogger's CS I/O ME baud rate matches that being used by the computer/LoggerNet. When other devices are also connected to the datalogger's CS I/O port, it may be necessary to lower the baud rate used for the SC32B. If you encounter communication issues, consider starting at 9600. If communication is successful, you can increase the baud rate until communication problems return. 5. Application The SC32B provides a direct interface between the CS I/O port on a Campbell Scientific datalogger and the RS-232 port on a computer. Some Campbell Scientific dataloggers (for example, the CR23X and CR5000) have a built-in RS-232 port in addition to the CS I/O port. With these dataloggers, the SC32B is only necessary if you wish to connect to the CS I/O port instead of the RS-232 port. The SC32B blocks data sent out the CS I/O port when the datalogger sets the printer enable/SDE (pin 6) high. The SC932 or SC932A (CS I/O to RS-232 DTE interface) can be used to interface to an RS-232 modem. 3