Questions about the transmission distance of instrument signals? ?

Choose a thicker cable; it should be able to support a transmission distance of 1000 meters. Generally, there is no problem with that. A rough calculation can be done: the transmitter can operate at 17 VDC, so 24 – 17 = 7. Then 7 / 0.02 = 350. Dividing 350 by the resistance per kilometer of cable (for example, 100 ohms) gives 3.5. Therefore, the maximum distance is 3.5 kilometers, though 1 kilometer is definitely no problem.

Theoretically, it should be within 2000 meters; in practice, a transmission distance of 500 to 600 meters for the transmitter is also quite common. Of course, in design, efforts are generally made to keep the distance within 200 to 300 meters, and there should be no problems with that.

Above 1000 meters, the signal attenuation is too severe； It is generally kept within the 500 range. If the transmission distance exceeds 500 meters, it is advisable to use optical cables for transmission

If there are many instruments, using remote IO and transmitting data via fiber optics is a good solution； If there are few signals, use bus instruments directly and transmit via fiber optics. The general principle is that for long-distance signal transmission, hard wiring is uneconomical and unreliable ； Converting to digital signal communication is the correct solution.

I’ve never heard of any repeaters being used for transmitting analog signals (a repeater is a component in communication networks that enhances communication signals to enable transmission over longer distances). Since the length of instrument cables generally does not exceed 400 meters, for analog signals, the relevant specifications must be followed – for example, 2.5 m² cables should be used for solenoid valve signals, while 1.0 m² cables are sufficient for 4–20 mA signals. With the use of fieldbus systems, it’s possible to transmit signals over greater distances, up to 1200 meters or more; after all, fieldbus is essentially a type of communication network, and communication signals are transmitted along the bus. In such cases, repeaters can be used. With twisted pair cables, up to 500 meters can be covered using 4 repeaters, while with thick cables, 2500 meters can be covered with 4 repeaters. What you’re referring to is likely the fieldbus communication method. However, this approach requires significant investment in field instruments, and the cables have to be purchased from abroad; its use has only just begun in China, so it’s hard to say exactly how effective it is.:lol :lol :lol It’s better to use remote I/O systems; if the distance between the remote I/O units and the main unit is too great, simply adding repeaters will suffice. The number of repeaters available in a network is also limited – they cannot be increased indefinitely!

Agree with the view from the fifth floor: add remote stations, and connect them to the local stations using optical fibers. But for specific instruments, it depends on what kind of instrument it is; remote wireless transmission can also be used :) :)

Install a 24V DC power supply unit in a suitable location in the middle, and then add a safety barrier or distributor to relay the signals and also provide isolation. Of course, this adds another point where failures can occur.

It’s not that close; under normal conditions, transmission is possible over 8 km, and the transmission distance for PLC is also well above 400 m.

Yes, a voltage booster (1-5V, 4-20mA) can be used, but using a HART voltage booster makes it difficult to use in the later stages.