Lighthouse ApexPortable Operating Manual
4-2 248083440-1 Rev 5
RS485 Communications
RS485 should be used if the instrument is more than 50 feet from the
computer or is installed in an industrial network. To do so, an optional
RS485 cable must be used. Refer to Table 4-2 for specifics about the
RS485 standard.
Table 4-2 shows the Electronics Industry Association (EIA) industry
standards specifications.
Table 4-2 EIA Industry Standards for RS485 Communications
SPECIFICATIONS RS485
Mode of Operation Differential
Total Number of Drivers and Receivers on
One Line (One driver active at a time for
RS485 networks)
32 Drivers
32 Receivers
Maximum Cable Length 4000 ft (1,219.2 m)
Maximum Data Rate (40 ft - 4000 ft for
RS422/RS485)
100Kbs - 10Mbs
Maximum Driver Output Voltage -7V to +12V
Driver Output Signal Level (Loaded
Min.): LOADED
+/-1.5V
Driver Output Signal Level (Loaded
Max.): UNLOADED
+/-6V
Driver Load Impedance (Ohms) 54
Max Driver Current in High Z State
(POWER ON)
+/-100μA
Max Driver Current in High Z State
(POWER OFF)
+/-100μA
Receiver Input Voltage Range -7V to +12V
Receiver Input Sensitivity +/-200mV
Receiver Input Resistance (Ohms), (1
Standard Load for RS485)
>
12k
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