SVR DU
AL
™
U
ser
’s M
anual
43
If your product is under warranty it will automatically be repaired and
sent back to you .
12. How to Order Additional Products
You can order upgrades and additional products for the SVR Dual™
(when available) . To see product descriptions or order products, see
the Decatur Electronics Web site at www .DecaturElectronics .com or
call the sales office at 888 .428 .4315 .
13. Appendix A - RS485 Notes
Unlike RS232 which allows just one transmitter and one receiver pair,
RS485 allows multiple sensors (SVR Dual™) units to be connected
to the same bus . This has the benefit of using the least amount of
wiring to connect multiple sensors . Each RS485 sensor on the bus
can listen for a request of data addressed to that particular sensor
and only that sensor is allowed to respond . An additional benefit of
RS485 is noise immunity of the bus due to the differential signaling .
RS485 is defined as having a half-duplex bus which allows just two
wires to handle all communications to and from the sensors . RS422 is
similar to RS485 except uses 4 wires to form a full-duplex path on the
bus (using two wires for transmit and two wires for receive) . For use
of multiple RS485 units on the same bus, the MODBUS protocol must
be used or there will be bus contention as more than one receiver
will try to respond . The MODBUS protocol is already programmed
into the SVR Dual™ unit and can be selected via the configuration
program as : A5SNSNSS .SSSCS HEX WITH CHECKSUM If this
protocol is used, the serial number of the unit becomes the address
of the sensor . The configure program can be used to set this address
and supports addresses from 1 – 99
