Termintaing resistance 120 Ohm required for RS 485 network ??

[arbj2]

Hi,

I have two devices on a RS485 network, the network is two wire type (A,B, GND), the transceivers used are SN75LBC184 (TI make). The devices are 5 metres apart, and are placed in an industrial environment, where the electrical noise levels could be high.

I have not installed a 120 Ohm resistance at one end of the network as suggested by many technical articles. The cable used is not twisted core, but three core type (parallel). The ground line is connected to a 120 Ohm resistor and then other end of resistor to ground, same is done for the other device.

My question is a 120 Ohm resistance required between A and B bus lines ??

Thanks
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[FvM]

The answer depends on the baudrate which wasn't mentioned. Up to several 100 kBaud, a 5 m link will work well without termination resistors. But of course they don't hurt.

 

[arbj2]

Sorry I forgot that,

19200 baud.