In all the years of using household appliances, only the old vacuum cleaner motors had any noticeable effect - the TV over the air would get lots of "snow" scattered white noise on the signal. The water heater, and I have had tanks and instant on types, have relays that click seldom when not in use and sometimes quite rapidly when in use. Never had an interference problem. The stove switches lots of current and depending on the load and change in load, the click rate will change a lot. Over the air TV, and radio right there in the kitchen and no interference.
So here in the USA where everything is allowed except what causes problems, instead of the other way around as elsewhere, if there are no complaints or problems, there are no regulations. Attitude is Mind over Matter. If you don't Mind, it doesn't Matter... This email has been displayed using 100% recycled electrons and 100% pure virgin photons. ________________________________ From: Grace Lin <[email protected]> To: Mike Violette <[email protected]> Cc: [email protected] Sent: Wednesday, August 3, 2011 10:52 AM Subject: Re: [PSES] FCC Exempted Devices Good Morning, Mike, It is good to hear from you. I would like to share with you and members my findings/thoughts, based on some measurement I took lately. Turning on and off relays with 16A/heavy load (high current?) creates big spikes (clicks). The amplitude of the spikes does not comply with FCC §15.107 conducted emission limits (for continuous disturbance?). Turning on and off relays without load creates much smaller spikes (clicks). The amplitude of the spikes complies with FCC §15.107 conducted emission limits (with good margins). Most of household appliances are high curent devices. CISPR 14-1 / EN 55014-1 gives relaxation for click noise. In order to apply for the relaxation, click rate must be measured. Most of spectrum analyzers, from my understanding, have no capability to measure click rate. R&S has a free download software, "Click Rate Analyzer", for its certain models of the EMI receivers wtih FFT option (a +$8,000 option). My guess is: FCC exempts appliances in order not to increase labs' (tax payers') financial burden. Agree? If you agree with my thoughts, here is my question: should a 16A load device with relays be exempted? Thank you very much for sharing your comments. Best regards, Grace Lin On Wed, Aug 3, 2011 at 10:06 AM, Mike Violette <[email protected]> wrote: The appliance manufacturers had an effective lobbying campaign when the rules were written! Mike Violette Washington Laboratories & American Certification Body [email protected] +1 240 401 1388 On Aug 3, 2011, at 9:39 AM, Grace Lin wrote: Dear Members, Does anyone know the reason FCC exempts devices listed under FCC §15.103(d) as quoted below? “(d) A digital device utilized exclusively in an appliance, e.g., microwave over, dishwasher, clothes dryer, air conditioner (central or window), etc.” FCC KDB 772105 clarify the exempted household appliances: “Exempt household appliances are electrical machines intended for household tasks that assist persons in washing and drying clothes, household cleaning, cooking, or food preparation; or is equipment that is directly involved in conditioning the supply of household water and air (heating, cooling and humidifying) in a residence. This includes appliances such as a vacuum cleaner, washing machine, dishwasher, clothes dryer, air conditioner (central or window), etc. This exemption is limited to basic housekeeping appliances and is not intended to apply to all home-use products that may contain digital logic.” I wonder (and would like to learn from members) if the exemption is due to the discontinous disturbance as stated in the EN 55014-1 (CISPR 14-1), the emission requirements for household appliances in the EU. I list several paragraphs excerpted from CISPR 14-1: 2005 for reference: “Switching operations in thermostatically controlled appliances, automatic programme controlled machines and other electrically controlled or operated appliances generate discontinuous disturbance. The subjective effect of discontinuous disturbance varies with repetition rate and amplitude in audio and video presentation. Therefore distinction is made between various kinds of discontinuous disturbance. “(CISPR 14-1 Clause 4.2) “The limits for discontinuous disturbance depend mainly on the character of the disturbance and on the click rate N ....” (CISPR 14-1 Clause 4.2.1) “For discontinuous disturbance, the click limit Lq is attained by increasing the relevant limit L (as given in 4.1.1) with: 44 dB for N<0.2, or 20 lg (30/N) dB for 0.2≤N<30 “ Thank you very much for your time and look forward to your comments. Best regards, Grace Lin - ---------------------------------------------------------------- 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 http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - ---------------------------------------------------------------- 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 http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - ---------------------------------------------------------------- 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 http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]>
