Answered: Your Most Burning Questions on What Is Rs485 Cable > 자유게시판

It does not specify or recommend any communications protocol; Other standards define the protocols for communication over an RS-485 link. RS-485, also known as TIA-485(-A) or EIA-485, is a standard, originally introduced in 1983, defining the electrical characteristics of drivers and receivers for use in serial communications systems. These manufacturers all agree on the meaning of the standard, and their practice is in widespread use. I don't see a problem the wire I use has 2 wires and a shielding which is the ground. I measured 77 VAC from the protective ground to the well head. This can be either by a wire between the two units or a wire on each unit to the read ground ( Earth ). There are several, notice the one in your circuit is Earth, there is only one Earth. The power company investigated and discovered that a power pole close to the well, and carrying a transformer, had a faulty earth connection.

The capacitance is close to 12.5 pF/foot but there is a small impedance mismatch (100 ohms for Cat 5, 120 ohms for RS-485). The value of each termination resistor should be equal to the cable characteristic impedance (typically, 120 ohms for twisted pairs). Or 4 wires and there twisted pairs. Not quite, the twisted pair ensures that any signal picked up is common to both wires. The function of the signal ground wire is to tie the signal ground of each of the nodes to one common ground. Are you saying only connect shield to ground at one end? In a single phase system, analog and digital instruments are selected to measure voltage, current, frequency, and power factor. The sizing of the measurement system begins with knowing the main parameters of the plant; in particular, from the characteristics of the protection switch, the type of distribution system, the rated current, the rated voltage and the type of busbar can be known. RS-485 only specifies the electrical characteristics of the generator and the receiver: the physical layer. These characteristics include: definition of a unit load, voltage ranges, open-circuit voltages, thresholds, and transient tolerance. RS-485 standard conformant drivers provide a differential output of a minimum 1.5 V across a 54-Ω load, whereas standard conformant receivers detect a differential input down to 200 mV.

Because of the differential signal, any noise is subjected externally to the cable is basically subjected to both cables. As a rule of thumb, the speed in bit/s multiplied by the length in metres should not exceed 108. Thus a 50-meter cable should not signal faster than 2 Mbit/s. Star and ring topologies are not recommended because of signal reflections or excessively low or high termination impedance. Termination resistors also reduce electrical noise sensitivity due to the lower impedance. It produces the result identical to the lower part of the Structure View data visualizer, but does not display any UI, writing raw data directly to the file. It displays data that comes from one end of the virtual link in the top pane and data that comes from another end in the bottom pane.The contents of each pane can be copied into the Clipboard or exported into the file in various formats.Its unique data filtering capabilities make this visualizer a very handy serial bridge protocol analysis tool. This exporter parses captured serial port data according to the loaded set of protocols, applies optional protocol-based filtering and Root Protocol and writes the resulting text data into the output file.

Custom visualizer receives each packet parsed according to selected protocol and adds one or more text strings to the output. The application's various editions include features for filtering, browsing, searching, recording, and data playback.Serial Monitor provides not only a wide range of visualization tools for popular serial protocols (including PPP, MODBUS, BACnet MSTP) and raw data, but also utilities for creating your own custom visualizers, allowing you to parse any data and custom protocols in a convenient way. Since our product allows you to parse and log serial data coming from multiple serial devices connected to the PC or even remote ones using your local or Internet connection, it can be used as a foundation for building various integration solutions based on it. By using repeaters very large RS-485 networks can be formed. RS-485 and RS-422 can interoperate with certain restrictions. In contrast to RS-422, which has a driver circuit which cannot be switched off, RS-485 drivers use three-state logic allowing individual transmitters to be deactivated. For an off, mark or logic 1 state, the driver's A terminal is negative relative to the B terminal. However this contradicts the facts that an idle mark state is a logical one and the termination polarization puts B at a higher voltage in Profibus guidelines.

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