In this article, we’ve presented a number of effective low-cost (thrifty) test instruments that can be used for EMC testing for both pre-qualification and troubleshooting, along with application examples that validate their usefulness. In an anechoic chamber, the antenna is much farther from the DUT and harness than in this homemade chamber, and proximity coupling with DUT variation is less of an issue.įigure 11: ESD gun applied to IC pins Summary and Conclusion Since we are only using the TEM cell to assess “before and after” results from any fixes, any discrepancies can usually be ignored as long as the DUT and harness locations are controlled (i.e., consistency in DUT positioning and orientation). However, it has been used with success in finding fixes for frequencies greater than 1 GHz. In Figure 6d, looking at the S11 and voltage standing wave ratio (VSWR), it appears that this TEM cell is only useful for frequencies less than about 200 MHz. This opening is to help isolate the source of the noise (DUT, harness, or both) by allowing placement of the harness outside the TEM cell. Figure 6b shows a small opening in the door. The center plate height is adjustable to accommodate different DUT sizes (default is in center between top and bottom). The dimensions are 16 x 16 x 37 inches, with a center plate (without end tapers) of 32 x 13.5 inches. This homemade cell is made from HVAC sheet metal ducting available at many home improvement stores. Although this VNA has a lot of capability, I used it for input impedance (S11) and VSWR measurements in the testing on which this article is based.įigure 6c: TEM cell variant, end taper and BNC connection detail It can be used as a standalone unit via touchscreen, but it is best used with free software QT and Saver. Even though this VNA typically costs less than $150, it is useful from 50 kHz to 3 GHz and comes with cables and calibration terminations. Figure 1 shows an example of such an instrument (the NanoVNA 2). One of the low-cost instruments discussed in this article is a vector network analyzer (VNA). Thrifty Test Equipment Vector Network Analyzer Identifying issues early allows maximum flexibility to experiment and provides sufficient time to make cost-effective changes before a design is frozen and difficult to change. Although the thrifty method is mainly used to compare results before and after implementing a fix (not meeting a specification limit), with some experience it can also be used in the pre-qualification development stage early in the design cycle to identify potential issues before formal lab testing. 1 This article offers some other test equipment options that have different capabilities and which can be even less costly. There are several excellent resources for troubleshooting methods and building a low-cost EMC toolkit. But inexpensive test equipment and procedures (let’s call them thrifty methods) used for helping to solve these EMC issues outside an EMC lab are very desirable especially if no in-house EMC facilities are readily available. Obtaining a cost-effective solution to these EMC issues may be time consuming, and many EMC labs can be fully booked or have limited availability, have long lead times, or involve significant costs. Issues related to electromagnetic compatibility (EMC) are often identified during qualification testing in an accredited EMC test lab which typically occurs late in the product design cycle. Low-Cost Instruments and Procedures to Troubleshoot EMC Issues
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |