이름 : Otto Schiller
이메일 : ottoschiller@googlemail.com
연락처 :
예식일 : Five Methods Rs485 Cable Can make You Invincible
문의내용:

It is interesting to measure the humidity of the ground, but we have also thought about other things; and then we have TXtemp to measure the temperature (one of the uses of TXtemp is in association with SuperClock), and for practically any type of measurement we have TXdata (RS232, RS485 ModBus) - which can be connected to thousands of existing third-party professional RS232 or ModBus meters (and there is something for all needs: temperature and humidity meters, anemometers, voltage meters, energy, light meters, water meters, presence sensors, brightness sensors, soil humidity sensors, rs485 cable etc. ; practically all professional meters are available in ModBus or RS232 standard; and not just meters). The TESTER-CCTVPOE-P Professional CCTV Tester with Power Over Ethernet (PoE) and IP Testing is a portable, multifunction tester for CCTV installations and maintenance. LAPP UNITRONIC ® BUS LD FD P cables are built after the RS-422 and RS-485 standards and are robust solutions for transmitting data over long distances and noisy environments. Using the FT232R chip combined with an RS485 level converter, the cable is CE, FCC and UKCA approved product which is one of the simplest USB - RS485 solutions around. Weird question but I'm buying the twisted pair cable for an RS485 system.

The RS422 standard is a standard for high speed and/or long distance data transmission that is generally used between one transmitter receiver pair and one other transmitter receiver pair, but each output can drive ten receivers. PWBS331 DC transmission data bus chip achieves the function of delivery both of the UART data and DC power on only two wires. It discusses using level converters like MAX232 for interfacing digital devices to RS-232 and decoding serial frames using a microcontroller UART. It also describes the features of PC serial ports, including EIA RS-232C specifications, serial vs parallel port differences, null modem configuration, and RS-232 waveforms. Converters between RS-485 and RS-232 are available to allow a personal computer to communicate with remote devices. Because they are produced in such large quantities, Cat 5 cables are relatively inexpensive, rs485 cable often less than half the price of specialty RS-485 cabling. The transmission speed of RS485 cables can vary depending on factors such as cable length, baud rate, and the quality of the cable itself. It contrasts serial versus parallel communication and asynchronous versus synchronous transmission.

It discusses connecting the microcontroller to a PC using a serial cable and level shifter for debugging serial communication. This document discusses serial communication using the 8051 microcontroller. Universal Asynchronous receiver transmitter is a device used for serial communication in various devices. Master drivers for RS-485 must be placed in the middle of slave devices to take advantage of the standard’s impedance guidelines. The value of each termination resistor should be equal to the cable characteristic impedance (typically, 120 ohms for twisted pairs). Differential pairs may host up to 32 devices on the standard that uses twisted pairs and a reference. If A is negative with respect to B, the state is binary 1. The reversed polarity (A positive with respect to B) is binary 0. The standard does not assign any logic function to the two states. A (green, negative) is higher than B (red, positive). The cable recommended in this type of connection is the Belden 9842, which has 2 twisted pairs.

The standard defines differential pairs for data transmission. Half-duplex allows transmission in one direction only. As stated in the standard, a combination of signal A being low while signal B is high defines transmission of a logic 1. This is called "Mark." The reverse is true for logic 0, called "Space." This is illustrated in the figure below. Cables use two-wire twisted pair to maintain optimum magnetic flux characteristics of the signal. If high noise immunity is needed, often a combination of twisting and shielding is used as for example in STP, shielded twisted pair and FTP, foiled twisted pair networking cables. Differential signals and twisting allows RS485 to communicate over much longer communication distances than achievable with RS232. Because of this RS485 and the others can be used in situations with a severe ground level shift of several volts, where at the same time high bit rates are possible because the transition between logical 0 and logical 1 is only a few hundred millivolts.