Hi Barry et al, I'm I missing something here? Is this exercise worth the trouble? If one doesn't have a clear margin to any commercial limit line with any kind of resistive dummy load attached to your LISN shouldn't you examine the your system setup? Accurate determination of your measurement system noise floor with a known impedance through the frequency range is really only of academic use in this case, isn't it? This should have no bearing on pass/fail of an EUT as the measurement system noise floor and the limit line should be well separated for conducted emissions in a shielded room.
Regards, Kevin Harris > -----Original Message----- > From: b...@namg.us.anritsu.com [SMTP:b...@namg.us.anritsu.com] > Sent: Friday, October 09, 1998 1:33 PM > To: emc-p...@ieee.org > Subject: Re: Shield Room Grounding > > Hi Ed, > > I appreciate your kindness to share your experience with us about > constructing equivalent load: "I constructed a load bank consisting of > 16 > surface mount light bulb sockets, all wired in parallel. I just screw > in an > array of 25/60/75/100 Watt rated lamps until I get the necessary > current. > Sure, there's some unknown slight lead inductance and capacitance. But > all > I want to do is draw a few amps DC" > > I have two questions: (1)What is the impedance of your bulb array at > 30 > MHz? i.e., Zb=? @30 MHz. (2)What is the impedance of EUT at 30 > MHz? > i.e., Ze=? @30 MHz > > If we are not sure Zb=Ze @30 MHz, I am afraid, it's hard to say the > spectrum analyzer would receive the same RF emission at 30 MHz from > noise > sources other than EUT, although the bulb array draws the same current > at > 60 Hz as EUT does. In other words, Zb=Ze @60 Hz is one thing, and > Zb=Ze > @30 MHz would be another. > > Let's see an example, assuming > Ze=Re+jXe, where Xe=Omega*Le, and Omega=2*Pi*F. > Re=20 Ohm, Xe=0.1 Ohm @60 Hz, Ze=20+j*0.1=>20 Ohm > Be=20 Ohm, Xe=50000 Ohm @30 MHz, Ze=>j*50000 Ohm > > Conclusion: As far as the equivalent load is concerned, we can only > pay > attention to the equivalence of resistance part of Zb and Ze @60 Hz. > At 30 > MHz, however, we should pay more attention to the equivalence of > reactance > part of Ze and Zb instead. > > Suggestion: We might need to check the equivalence of Zb and Ze @30 > MHz by > using an Impedance Analyzer, e. g., HP4191A(?). > > > Thank you. > Please correct me. > Best Regards, > Barry Ma > > --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
