From: "Terrell W. Fritz"
Date: Sun, 14 Jan 2001 21:28:47 -0700
Subject: Re: [TSSP] Top voltage testing
Hi Paul, The bare coil: Fo = 147.745 kHz Iin = 1.5095 mARMS Vin = 0.706 VRMS With YT5060 probe attached: Fo = 105.050 kHz Vtop = 54.5 VRMS Vin = 0.706 VRMS Iin = 1.091 mARMS Bandwidth Q Vtop = 69.8 YT5060 through ~1 meter 30ga. wire Fo = 95.309 kHz Vtop = 55.9 VRMS Vin = 0.706 VRMS Iin = 1.335 mARMS Bandwidth Q Vtop = 74.055 Bandwidth Q Iin = 78.36 For the last Q measurement I used the current input multiplied by 0.7071 to find the Q but got a different answer than using the top voltage. If this method is valid, it may be more accurate than the voltage from the scope since the HP meter has far higher resolution and accuracy. Do you think using the input current as a measure of Q is valid and should it be equivalent to the top voltage Q? If so, that would probably be a far better way to measure Q. However, I went back and double checked and the input current Q and top voltage Q are significantly different! There is a 0.995 surface mount resistor in series with the generator output, so the driving impedance is around 1 to 2 ohms. I also noted that the metal knob on the signal generator causes a bit of frequency drift when I touch it. I will change it to plastic... At 10:00 PM 1/14/2001 +0000, you wrote: >Terrell W. Fritz wrote: > >> I would like to disqualify the earlier P6015 probe voltage level >> measurements. > >Well that's a relief. Would have been hard to account for the low >voltages. > >> The modern 10X probe seems to work very well and I trust it rather >> than the big high voltage probe in this case. > >Yep. It claims 16.6pF and it's taking 24.35pF of extra top cap >to account for it. That's not too bad an impact on a large coil. > >Some of the excess capacitance might go away if you fix the scope >probe to a stand, at coil-top height, say a coil length away. Run a >very thin wire from coil top to the probe. That ought to cut down the >capacitance from the coil to the probe body. > >Perhaps you can find time to get some with/without YT5060 readings >from a bare coil, along with Q and input current? > >Cheers, >-- >Paul Nicholson, >Manchester, UK. >--
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.