From: "Terrell W. Fritz"
Date: Tue, 09 Jan 2001 20:24:56 -0700
Subject: Re: [TSSP] Top voltage testing
Hi Paul, At 01:07 PM 1/9/2001 +0000, you wrote: >I asked: > >> >Did you happen to note the base input current or the V drop >> >across your pad resistor - not essential but useful for >> >autopsy if the gain prediction doesn't match. > >Terry wrote: > >> I drove directly from the low Z (<1 ohm) signal generator. >> Putting a 1 ohm surface mount resistor in the signal path with >> the HP meter would be easy if needed. > >Looks like we might need that base current reading as we have a >discrepancy (dont we always :)) to sort out. My last post had the bare coil current. > >There's a problem with the voltage gains. The voltage gain should >(according to pn2511 theory and the model) be a little higher than >the Q factor, eg for test #1, Q=93 and the predicted vgain is 96.1, >your measurement with the P6015 probe gives only 76.2, a 26% >difference. Similar for test #2 also. > >Test #3 does better, with a Q of 73 the predicted vgain is 74.5 and >measured is 76.2, a 2.3% difference, which is reasonable. > >Also, going back to your NSVPI terminated coil results, your total >voltage gradient after adding 0.12v for the diode drops, comes to >around 155.4 volts - a vgain of 155.4 for a predicted 168.5 volts. >Again the vgain should have been slightly higher than the >measured Q of 163.8, thats a discrepancy hard to account for at >either my end or yours. > >So far the only vgain comparisons that match are your NSVPI bare >coil results, and the test #3 data from the regular scope probe. The TEK P6015 is a $1200 probe but mine was free at a hamfeast ;-)) As far as I can tell, it works perfectly but.... > >Can you check that the P6015 and YT5060 probes agree on the voltage >when they simultaneously measure the same voltage. Could your >P6015 be open circuit somewhere, so that we only got a capacitive >pickup perhaps? I plugged them both into the AC line: http://hot-streamer.com/temp/probeCompare.gif They appear perfectly identical. I subtracted one from the other and turned up the gain but the tiny spiky stuff at very low levels looks like digital noise in the scope's sampling rather than error. The P6015 seems perfect... However, I still just have a "gut feeling" that the error we see in it's measurements of the secondary is not accurate and the P6015 is somehow disturbing the coil. Cheers, Terry > >I might have a problem with the predictions, but if so its a serious >one, as the vgain > Q trend is a fairly basic result which is >expected for all coils with medium or large h/d. > >The comparisons for tests #1 and #3 are in > > http://www.abelian.demon.co.uk/tssp/pn0801.html > >Maybe you can check the probes and also obtain a base current >readings - they should be consistent with the input resistances >given in pn0801. > >Cheers, >-- >Paul Nicholson, >Manchester, UK. >--
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.