**2. EMC pre-compliance measurements**

Data from EMC testing laboratories report that 85% of products submitted for final EMC compliance testing fail for the first time. However, using pre-compliance EMC measurements, it is possible to reverse these statistics so that products pass EMC tests successfully [9].

Performing pre-compliance measurements significantly increases the probability of a successful first transition to complete EMI compliance testing, saves time and money. Large companies developing products for medical, automotive, military, and other industrial applications perform pre-compliance measurements as part of a standard procedure. Small companies and startups are starting to follow this way as well, as they can benefit from investing in setting up pre-compliance measurements.

Pre-compliance EMC measurements can define as the ability to perform internal testing of EMC products before going to the final certified testing laboratory. In doing so, pre-compliance measurements can be performed by the manufacturer either internally or in agreement with an experienced development laboratory.

Of course, there are even more reasons to do pre-compliance measurements, which are as follows:


**Figure 2** shows very clearly an example of the process of product development using pre-compliance measurements. Whether the product passes the individual stages of development or not is determined by the results of not only pre-compliance measurements. Although pre-compliance tests may seem to have only advantages, they have a higher measurement uncertainty than compliance EMC tests due to their simplification. However, this disadvantage is many times compensated by savings not only in money but especially in time during product development.

More complex electrical equipment contains several functional blocks, such as power supply circuits, switching power supply, input/output (I/O) circuits, sensitive analog circuits, digital circuits, high-frequency (HF) circuits, converters, peripherals, control circuits, I/O connectors, and filters, reference ground plane. These circuits must arrange in such a way that they do not interfere with each other and that they are at the same time sufficiently immune to external electromagnetic fields. **Figure 3** shows an example of the optimal arrangement of circuits on a PCB in compliance with EMC principles.

The precise design of a printed circuit board (PCB), and the selection of quality components, play a significant role in the product prototype design. The PCB designer must have good experience to eliminate interference generation by precise PCB design. Currently, CAD software can use in PCB design, which provides the ability to select different tracing strategies. In the design of PCBs, the generation of Joule losses and methods of loss dissipation must also take into account.

Some researchers are working on methods for diagnosing and managing enhanced EMC for a specific area of EMC, such as mobile phones. The authors in [10] constructed a knowledge graph that presents interference and sensitive units based on mathematical rules. EMC diagnostic and management reports are generated by searching knowledge graphs with an extracted entity and parameter information. The authors performed an experiment and found that the proposed intelligent method of EMC diagnostics and control significantly increased the efficiency of the calculation, saved storage space, and increased the accuracy of identification.

**Figure 2.**

*Product development cycle; the meaning of capital letters is: T – true, F – false.*

*EMI Pre-Compliance Measurements Reveal Sources of Interference DOI: http://dx.doi.org/10.5772/intechopen.99754*

#### **Figure 3.**

*Circuit layout on the PCB in compliance with EMC principles: 1 – The necessary connections must filter, 2 – The reference ground plane located below all elements and conductive surfaces.*

#### **2.1 Solving EMI problems during pre-compliance measurements**

When solving EMI problems during pre-compliance measurements, engineers face several challenges. Some EMI problems can be detected and eliminated relatively quickly and easily; some are more complicated and time-consuming. Therefore, engineers must address the technical side of the problem along with the requirement to minimize costs. Remember that each metal wire in an electrical circuit acts simultaneously as an EMI source and an EMI receiver. Thus, any interference can affect the electrical equipment either by metallic conductors or by electromagnetic waves. A distinction exists between EMI by conduction (conducted Interference) and EMI by radiation (radiated interference).

Radiated interference is due to radio noise or unwanted signals over the air, not through a physical medium. Conducted interference is due to conducted radio noise or unwanted signals entering a victim by direct coupling (via cables).

According to the IEV 161-03-28, a radiated disturbance is an electromagnetic disturbance for which the energy is transferred through space in the form of electromagnetic waves; IEV 161-03-27 conducted disturbance is an electromagnetic disturbance for which the energy is transferred via one or more conductors. IEV 161-01-05 defines electromagnetic disturbance as an electromagnetic phenomenon that can degrade the performance of a device, equipment or system, or adversely affect living or inert matter [1]. Strategies based on theoretical knowledge of circuit technology, micro-electronics, and professional experience are used to detect EMI sources. The EMI problems that need to address are closely related to the electromagnetic couplings between the source and the victim. The procedure can be as follows:

1. all EMI sources must detect on the PCB,

2. check interference levels in all metallic conductors,

3. short-distance EMI verification of the prototype (1 m or 3 m).

**Figure 4.** *EMC base chain.*
