Use Digital Storage Oscilloscope to test RS485 signal, following the figure:
Digital Storage Oscilloscope, 4 channels, 2 analog channels, 2 digital channels.
This unit is a 5-trace 4-channel digital oscilloscope for common electronic engineering tasks. Its CPU is based on ARM Cortex M3, adopting FPGA to manage the control & data buffering of ADC. A built-in 2MB USB disk enables users to store waveforms & upgrade firmware. It also provides 4 application areas, convenient for users to load & upgrade at most 4 kinds of application firmware.