Hi,
If using RS-232 then again what protocol I need to use ?
It´s independent of RS232 or RS485....you have to speak the language of the device you wan t to talk with.
So if you want to communicate with the BK precision device you need to use it´s protocol.
If you want communicate with TC-140, then you need to use it´s protocol.
Maybe it uses some standard communication protocol .. but who knows? --> the manufacturer.
But even a standard protocol uses a standard "language". But you can´t be sure that both partners understand all commands.
It´s like with human beings. English is not my mother tongue. But I´ve learned some words ... so I can communicate a little here in this forum. But for sure I don´t understand
all words.
Back to your devices:
Maybe the protocol uses ASCII signs, then - with a terminal software - you can read text. Maybe you understand the text, maybe not.
It could be MODBUS, but even then you need to understand the meaning of the transmitted bytes.
The same is with Profibus or other standard protocols.
In short: you need the manufacturer. He is (has) the "dictionary" that explains the transmitted bytes.
Klaus