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Appendix - B
RS-485 Adaptor Board Electrical Specifications:
Input Voltage Requirements:
5.00 volts ±0.50 at J1-5 (+) and J1-6 (-).
Current Requirements:
A source capacity of 200mA is recommended. Typical current draw for the board
is 68mA with the transmitter driving a 120 ohm load, and 26mA with the load
removed.
Isolation Voltage:
1250 Vrms isolation exists between the J1 connector and the TB1 connector. The
limiting element here is the transformer T1 that is hipot rated at 1250 volts.
Maximum Data Transfer Rate:
Limited to 400k bps due to the isolation barrier architecture within the RS-485
conversion IC. The CNI board design further limits the serial data exchange rate
at 38.4k bps maximum.
Transmitter Drive Levels:
Typical measured values are 6.20 volts with no load, and 4.02 volts when driving
a 120 ohm load.
Receiver Sensitivity:
200mV sensitivity minimum.
Receiver Input Impedance:
68k ohms typical, representing approximately 1/4 unit load.
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