Why My RS485 Standard Is Better Than Yours > 자유게시판

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, etc. ; practically all professional meters are available in ModBus or RS232 standard; and not just meters). The UART Wildcard provides two simultaneous communications links, each configurable as RS232, RS485 or RS422. Many references and examples are made to "asynchronous start-stop communication with a UART" or "UART" communications. These examples are for a single 120 Ω termination. In other applications, RS485 standard the RE and DE pins are separate. A separate logic supply pin VL allows the LTC2870 and LTC2871 to interface with any logic signals from 1.7V to 5.5V. All logic I/Os use VL as their high supply.

At the UART, a logic high (5 volts) is called a mark, and a logic low (0 volts) is called a space. These cables generally contain one or more twisted pairs as well as ground shields or a ground wire (sometimes called a drain wire). Working modes: Asynchronous half-duplex(RS485) or asynchronous full duplex(RS422),no need jumper wire settings. RS232 signals are driven on a single wire with respect to ground at levels that must exceed 5V and -5V. The serial RS232 to RS485 converter and RS232 to RS422 converter units, also called serial converters, are small electronic devices used to convert a serial RS232 signal, (for example the COM port in older computers) into either RS485 or RS422 signals. But, since one of outputs goes high when the input goes high, it is often called the "non-inverting" output. Idle Bus. All drivers on the bus are disabled with high impedance outputs. When RS485 termination is enabled on the LTC2870 or LTC2871, the 120Ω differential resistors are connected across receiver inputs A and B and also across driver outputs Y and Z. The driver termination is not strictly necessary for the case when this device is actively driving the bus, such as the master in Figure 7. However, the Y to Z termination is necessary in applications such as the slave at the far end of the bus in Figure 7, where another device is driving the bus.

For decades, their customers have put a mechanical device on the tank. This problem can also be fixed by adding bias resistors to force the line to idle condition when a driver is not connected, but this has to be done on a network basis, not a device basis. • Devices identified by DECK Monitoring Engineering as inducing noise into the Modbus network shall require each require one (1) approved RS-485 Optical Isolator. Biasing will also improve noise rejection. The higher the data rate and the longer the cable, the more likely it will be that you have to add termination resistors. This will decrease the amount of time to wait for the signal to stabilize, increasing the possible bit rate. If the transition time of the signal driven into the bus is significantly less than the round trip delay to the load and back, then the bus needs to be terminated differentially with a resistor whose characteristic impedance matches that of the bus. Diagnostic and maintenance data such as lamp burn time is also readily available. RS422 allows one transmitter and up to 10 receivers with data transmission rates up to 10 Megabits per second for distances up to 40 feet and up to 100 Kilobits per second for distances up to 4000 feet (1219 metres).

Figure 8 shows the results of using the LTC2871 internal 120Ω termination resistor to terminate 100 feet of CAT5e cable compared to the same cable terminated with 100Ω. Although the internal terminator is not a perfect match for the 100Ω cable, there is almost no effect on the overall signal other than a slight amplitude increase at the beginning of the received signal, which can improve system performance via increased signal overdrive and noise margin. The balanced receiver architecture permits transmission over longer cables than an unbalanced receiver and offers the additional benefit of excellent noise immunity due to the wide effective differential input signal hysteresis of 130mV for typical communications. Scope traces on the top show the differential signal at the driven end of the cable (Y - Z) and the bottom set of traces show the differential signal received after traversing the cable (A - B). The figure also shows the devastating effect of leaving the cable unterminated at the receiving end, where reflections degrade the signal substantially. For instance, the effect of using a 120Ω termination on each end of a 100Ω cable is to develop an overshoot of about 10% at the receiver end with a duration equal to twice the one-way propagation delay in the cable.