What is the impact of high frequency noise on electronic security systems? That depends…
A: How the installation team ascertains what impact HF noise is having on a security system comprising many susceptible parts is a complex business – it’s going to depend on the sensitivity of components, the design of device circuits, cable route, the nature of the install, the nature of the environment.
It’s easy to point out the effect high frequency noise has on circuits in the laboratory, but it would be unwise not to concede that such effects vary widely in the field. Taking this into account, there are a number of predictable impacts of HF noise.
At the device level, one issue may be loss of digital logic noise margins. Most well-designed systems have a noise margin built into digital circuitry allowing them to operate properly in the presence of noise generated internally or externally for short periods of time.
A constant barrage of EMI will scour this margin away and EMI spikes breaking through the circuit’s tolerance will cause random and unexplained malfunctions. The same noise may impact on wireless communications supporting security systems, leading to comms dropouts and range reduction.
At a component level, circuitry could also be combining its own noise with the noise generated by nearby components or emanating from environment, to create EMI of unexpected frequencies. These joint emissions could impact on boards and devices with strange results.
Reliability is another victim of noise. Component failure can be caused by voltage undershoot on a clock waveform shunting an IC. If this undershoot breaches an IC’s tolerance over a period of time, malfunction or failure (leading to system failure) will result.
When troubleshooting, installers and security managers should look out for problems that that can’t be attributed to the normal operation of the equipment. They should also look out for HF noise generating systems and devices, search for HF noise routinely, encourage HF noise emitters to incorporate noise traps, and design systems that incorporate protections and filters.
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