Hi All, It turns out the signal generator has an average output of only mW, but a peak power of 5000W or so. This is a small battery powered hand-held EFT like pulse generator, from Fischer Custom Communications, that I use for circuit troubleshooting. It will deliver thousands of Watts of peak power into 50 Ohms! The pulse is somewhat shortened from a standard EFT pulse to allow the use of 2 Watt attenuators. However, to minimize the stress on the attenuators they should be positioned as follows from the output of the generator: 3, 6, 20 dB. That way the 20 dB attenuator is more likely to survive and can even be a ½ Watt rating. If placed first, It will take most of the power and may not survive.
EFT and especially ESD have extreme peak to average ratios and for signals like this, the lowest attenuation attenuators should be used first. Separately, I have a few guidelines for ESD or EFT debugging: * Generally, it is not very efficient to debug these problems on the official test sites. If this is done, in my experience, the solution will take a lot longer, may not be well understood, and likely cost more (because it is not the best solution). * I usually do not consult system documentation in the early stages of debugging, an inefficient use of time. * I inject voltage via mutual inductance or current through 1-2 pF of capacitance, known levels of noise into the circuit (I know how much signal the circuit is stressed with even though I may not yet know the circuit details). The injection, for mutual inductance, must have a short range, ¼ inch or less. * I find the part of the circuit causing the problem and then consult the documentation to finalize my fix. In one case it was a 20 pF cap to circuit ground. At that point, I had no idea of the circuit and why the fix worked until consulting the documentation. It took me 5 minutes to localize the problem to one single node in the circuit before consulting the documentation. That is after another consultant could not find the problem after 4 days of work using the conventional engineering methods we all know. * ESD/EFT like, but low level and no circuit contact, noise with close in injection is a very powerful technique for debugging a circuit that has an ESD/EFT problem. I have been fine tuning this procedure for about 40 years now. Doug [https://lh4.googleusercontent.com/_HuR3Ky2TF_XhFHyxnYRmiq7nHQldnMsPNYFaLG6kb5T4y8MeCe-BDC_BscJtSFgszSSjssihHS-pjM3-jwNP8S0CwE-gN8fsRsPkojiAlmpBwb20vIVizS-siCUywW_jqrefbVr] From: Richard Nute <[email protected]> Sent: Monday, July 24, 2023 13:51 To: doug emcesd.com <[email protected]> Subject: RE: [PSES] Order of attenuators Hi Doug: Since the source is 10 mW, and the attenuators are 2 W (I assume resistive, 50-ohm, see attached schematic), then any attenuator should be able to dissipate the 10 mW of the source. However, to minimize power dissipation in each attenuator, they should be arranged 3 dB, 6 dB, and 20 dB. Best regards, Rich From: doug emcesd.com <[email protected]<mailto:[email protected]>> Sent: Monday, July 24, 2023 12:15 PM To: [email protected]<mailto:[email protected]> Subject: [PSES] Order of attenuators Hi All, Here is a puzzle. I have a signal source of average power less than 10 mW and I want to put three attenuators on the output, 20 dB, 6 dB and 3 dB. All are two Watt attenuators. What order should I put them on to minimize the chance of burning some of them out? This is a situation I encounter during my circuit troubleshooting. Doug [https://lh4.googleusercontent.com/_HuR3Ky2TF_XhFHyxnYRmiq7nHQldnMsPNYFaLG6kb5T4y8MeCe-BDC_BscJtSFgszSSjssihHS-pjM3-jwNP8S0CwE-gN8fsRsPkojiAlmpBwb20vIVizS-siCUywW_jqrefbVr] - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: https://www.mail-archive.com/[email protected]/ Website: https://ewh.ieee.org/soc/pses/ Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to unsubscribe) List rules: https://ewh.ieee.org/soc/pses/listrules.html For help, send mail to the list administrators: Mike Sherman at: [email protected] Rick Linford at: [email protected] For policy questions, send mail to: Jim Bacher: <[email protected]> _________________________________________________ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
