What are the isolation measures for instruments and electrical communication signals?
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As the title suggests, for digital signals, relays are used for isolation. What about analog signals? Should a safety barrier or an isolation barrier be used? Also, are analog signals such as variable frequency speed control (AO) and speed feedback (AI) considered intrinsically safe signals?
Isolation barriers are used solely for the isolation of analog signals, and they are relatively inexpensive. If it is a hazardous area, a safety barrier is required. An analog signal is not an intrinsically safe signal by itself.
Firstly, safety barriers are divided into isolated type and Zener type. The AO and AI outputs of the inverter are not intrinsically safe signals; if you want to monitor the speed of the field control panel, you should use an explosion-proof control panel, as there is no need to install a safety barrier
Check whether the signal is in an explosion-proof area; if not, for signal stability, use an isolator for economical solutions. If it is in an explosion-proof area, the instrument must be intrinsically safe and used in conjunction with a safety barrier
Do not use a safety barrier in place of a signal isolator as a means for signal isolation in electrical instrument rooms; these are two different concepts, and their technical specifications also differ. Remember this!
Analog signals such as variable frequency speed control (AO) and speed feedback (AI) are not intrinsically safe signals. If the variable frequency system is isolated from these signals and meets the relevant isolation parameters, then it may not be necessary to use signal isolators in the circuit; however, in practical engineering work, there is often no time to verify such things. Moreover, signal isolators cost only a few hundred dollars, so they are usually included in the design.
It’s not as complicated as it is for you; I just use relays for isolation, and the analog signals from the frequency converter go straight into the card. Is it really necessary to make it so complicated? The more intermediate steps there are, the more troublesome it becomes.
It’s not a matter of complexity; signals coming from electrical sources are more likely to mix with high-voltage currents than those coming from other sources. You go straight to the card components – the hearts are really big!
It’s not a problem with an enlarged heart; you can check the frequency conversion cabinet – the analog signals coming out of that cabinet are also processed, so there’s no need to worry.