We also see that there is a maximum slew rate defined for both RS232 and RS423. First of all we see that the speed of the differential interfaces RS422 and RS485 is far superior to the single ended versions RS232 and RS423. But some of the other interfaces are certainly interesting because they can be used in situations where RS232 is not appropriate. Multimeter: You can use it to measure voltage and current on the RS485 lines, aiding in identifying wiring issues. Sig- line. The RS485 receiver compares the voltage difference between both lines, what is rs485 cable instead of the absolute voltage level on a signal line. Therefore the trigger level of the RS232 interface is set relatively high at ±3 Volt. RS485 drivers automatically return to their high impedance tri-state within a few microseconds after the data has been sent. 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.



































Default, all the senders on the RS485 bus are in tri-state with high impedance. Devices will be linked together via a bus configuration as shown in the picture above. Because there is a chance of data collosion with this implementation, theory tells us that in this case only 37% of the bandwidth will be effectively used. This is great for Supervisory Control and Data Acquisition (SCADA) systems where there are many devices and it also comes at a very low cost to implement. Low Cost: RS-485 is a cost-effective solution for serial communication. RS485 transmits binary signals by generating high and low voltages, representing binary 0s and 1s (on and off), enabling efficient long-distance communication in electronically noisy environments. It is also an ideal choice for industrial equipment use due to its high speed, reliability and safety. 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. Twisted pairs in RS485 communication however adds immunity which is a much better way to fight noise. One of the main problems with RS232 is the lack of immunity for noise on the signal lines.



































Connect the shielding net to the main communication wire shielding and then ground it. A: In RS485 wiring, it is essential to use twisted-pair cables with proper shielding to reduce interference from external sources. A: To prevent signal reflections in RS485 networks, it is essential to use termination resistors at both ends of the communication line. With RS485 communication distances of 1200 m are possible. In this situation, bandwidth can be used for almost 100%. There are other implementations of RS485 networks where every node can start a data session on its own. There is no need for the senders to explicity turn the RS485 driver on or off. With RS485 on the contrary there is no such thing as a common zero as a signal reference. Shielding-which is a common method to prevent noise in RS232 lines-tries to keep hostile magnetic fields away from the signal lines. The transmitter and receiver compare the voltages of the data- and handshake lines with one common zero line. Q: How does RS422 compare to RS485 in terms of communication capabilities? Anti-inteference layer: Rs485 cables are designed with 2 anti-inteference layers to shield the internal conductors.



































Rs485 cable is essentially a signal cable with a twisted pair structure, additionally shielded with 2 layers of noise protection used in industrial communication. This ensures maximum protection for the inner core. The maximum slew rate also limits the maximum communication speed on the line. For both other interfaces-RS422 and RS485-the slew rate is indefinite. For example, if the data rate is 100 kbps, the maximum cable length is 4000 feet. However, if the data rate is increased to 1 Mbps, the cable length is reduced to 400 feet. Although total cable length maybe shorter in a star configuration, adequate termination is not possible anymore and signal quality may degrade significantly. The RS485 network must be designed as one line with multiple drops, not as a star. TSB-89A, Application Guidelines for TIA/EIA-485-A does not recommend using star topology. In the picture above, the general network topology of RS485 is shown. In the picture above, noise is generated by magnetic fields from the environment. A: Twisted pairs in RS485 communication help reduce the effects of electromagnetic interference (EMI) by canceling out unwanted noise introduced in the communication channel.