Advantech Data Acquisition Modules ADAM 4000 Manual de usuario descargar pdf (Pagina 408)

100

101

Appendix E

Appendix E RS-485 Network E

-5

E. 2 Line Termination

Each discontinuity in impedance causes reflections and distortion.

When an impedance discontinuity occurs in the transmission line the

immediate effect is signal reflection. This will lead to signal distortion.

Specially at line ends this mismatch causes problems. To eliminate this

discontinuity terminate the line with a resistor.

Figure E-4 Signal Distortion

The value of the resistor should be a close as possible to the

characteristic impedance of the line. Although receiver devices add

some resistance to the whole of the transmission line, normally it is

sufficient to the resistor impedance should equal the characteristic

impedance of the line.

Example:

Each input of the receivers has a nominal input impedance of 18 kW

feeding into a diode transistor- resistor biasing network that is

equivalent to an 18 kΩ input resistor tied to a common mode voltage of

2.4 V. It is this configuration which provides the large common range

of the receiver required for RS-485 systems! (See Figure E-5 below)

1 2 ... 403 404 405 406 407 408 409 410 411 412 413 ... 428 429

Comentarios a estos manuales

Sin comentarios

Advantech Data Acquisition Modules ADAM 4000 Manual de usuario Pagina 408

Comentarios a estos manuales

Relacionado con productos y manuales para Hardware Advantech Data Acquisition Modules ADAM 4000