Does anyone know a tester for the RS-485?

Or some rules i must measure, like resistance..

Thanks in advance

 

Do you want to check the cable or the device? To troubleshoot RS485 system the best approach is to determine a device communication characteristics (two wire or four-wire system,device isolated or not, device terminated with EOL resistor or not, devices response time, baud rate ..ext). You can diagnose problems with the RS-485 bus using two methods :

1-Verifying RS-485 with a TimeTap: which is good troubleshooting device and using serial port of a laptop computer in addition to terminal emulator you can determine if RS- 485 data is present.

2- Verifying RS-485 with an oscilloscope multi-meter can't measure due to the frequency response ) The + and - Data lines are similar but just inverted from each other.

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