I wasn't going to weigh in on this but... what was presented by Mr. Umbdenstock is equivalent to saying that since 2 + 2 = 4, then 2 x 2 = 4. It is tautological. The decibel scale is a power ratio. If a signal has a particular duty cycle then it is the total power that is affected by the duty cycle ratio. If something is on 100% and then you reduce the on-time to 50%, clearly you consume half the previous POWER.
dB = 10 log (P1/P2) Let "a" be the duty cycle ratio, with 0<a<1, so that P1 = aP2. Then dB = 10 log (aP2/P2) = 10 log (a). QED. ---------- >From: [email protected] >To: [email protected], [email protected] >Subject: RE: duty cycle correction factors >Date: Thu, Oct 18, 2001, 12:26 PM > > > Stuart, > > Duty cycle in 15.231 is related to a voltage ratio, therefore 20 log(duty > cycle) will provide the correct factor. > > Demonstrate it to yourself. Start with a given value (say 100V), multiply > this by some duty cycle (say 15% or .15). Convert the result to dB. This > is your reference result. Now take 20 log of a duty cycle (.15). Convert > your given value (100V) to dB. Add the numbers together, duty cycle dBs to > the given value dBs, and behold -- the same answer as the reference result. > > Best regards, > > Don > >> ---------- >> From: Stuart Lopata[SMTP:[email protected]] >> Reply To: Stuart Lopata >> Sent: Thursday, October 18, 2001 12:00 PM >> To: emc >> Subject: duty cycle correction factors >> >> >> Part 15.231 devices use a duty cycle correction factor to adjust peak >> readings. The duty cycle represents the fractional on-time over a given >> period of time (that must be under some limit). Anyways, given this >> fractional time, d, how do you make the conversion to dB? >> >> 10log(d) or 20log(d)? >> >> There have been some misinterpretations, since the readings are made at a >> span of zero hertz (voltage readings). Normally, a reduction in voltage >> would use the 20log scale. However, since the duty cycle does not >> represent >> a scale down (it represents the off-time versus on-time), the 10log scale >> seems more appropriate. >> >> I have seen conflicting documents, so would like your professional >> opinions! >> >> Thanks, >> >> Stuart Lopata >> >> >> ------------------------------------------- >> This message is from the IEEE EMC Society Product Safety >> Technical Committee emc-pstc discussion list. >> >> Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ >> >> To cancel your subscription, send mail to: >> [email protected] >> with the single line: >> unsubscribe emc-pstc >> >> For help, send mail to the list administrators: >> Michael Garretson: [email protected] >> Dave Heald [email protected] >> >> For policy questions, send mail to: >> Richard Nute: [email protected] >> Jim Bacher: [email protected] >> >> All emc-pstc postings are archived and searchable on the web at: >> No longer online until our new server is brought online and the old >> messages are imported into the new server. >> > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson: [email protected] > Dave Heald [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > No longer online until our new server is brought online and the old > messages are imported into the new server. > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
