I don't have that type of meter. I did spot a diy LR meter for this but can't justify 100.00 bucks for it:
L/C Meter II, a digital inductance meter / capacitance meter.
thanks...
Could you explain this in a little detail, I'm going to be in this boat and am too stupid to know what you're getting at procedure wise. what does one do with the resistor and where/ how is the value measured, and with what?
Sorry for a dumb down request, I'm going to have to go through this unless someone finds a source for one in a "fixed" value.
Maybe the article will have a suggested part number?Thanks, hopefully others are wondering the same thing?
russellc
that's the one i have. it works quite well and was quite accurate compared to expensive and well maintained hp analyzers i had access to at my previous job some years ago.
best $100 i ever spent. but i know what you mean.
best,
mlloyd1
best $100 i ever spent. but i know what you mean.
best,
mlloyd1
I'm guessing that a matched pair for the diffamp (Q4 + Q5) is not a requirement
as P1 pot is used to adjust for zero offset. I could be wrong.
Wayne, should we have received 6 matched with each board?
Scuse me.
"in situ" is fancypants latin for "at location", you measure the cap while it's mounted on the board, 5pF is uncanny little.
The 5pF and the 1M resistor make a high pass filter, ~31.847 Hz with f = 1/(2*Pi*R*C) , dampens everything below that by 10dB per decade.
Means, if you feed the cap a signal from a sinus generator that's 1/10th of that frequency, you'd see an amplitude on the output that's 10dB smaller if the cap is 5pF.
If you use two known caps of different value, you can precisely figure out the stray capacitance of the board.
(stuff i had poly-u classes in, both math classes and audio amp electronics, so please don't see me as some wise-guy jinni)
my BOM for pearl2
I made this parts list so I could compare with what I have on hand. Feel free to check for accuracy. - it probably isn't. (I haven't double checked it myself yet)
Note that I did leave off Cx & Rx (C15 & R15). Most of this is from the silk. I only checked a couple items against the schematic. (like that the LED is red)
At least until the article I can start some planning.
Though I have many of the parts, at least a red LED
I'm pretty sure I don't have any of the FET's other than what comes from passdiy
and now it's
time - figure the rest out later...
I made this parts list so I could compare with what I have on hand. Feel free to check for accuracy. - it probably isn't.
(I haven't double checked it myself yet) Note that I did leave off Cx & Rx (C15 & R15). Most of this is from the silk. I only checked a couple items against the schematic. (like that the LED is red)
At least until the article I can start some planning.
Though I have many of the parts, at least a red LED
I'm pretty sure I don't have any of the FET's other than what comes from passdiy
and now it's
time - figure the rest out later... 
That's because he's dutch, w
e all have it, it's viral. 
This guy on Ebay has 5pF/100V silver mica capacitors with a tolerance of 10% that would be 0.5pF either way. The leads could fit any footprint. Probably should be just fine - good price as well...
5pF 5 pF 100V Radial Silver Dipped Mica Capacitor (25) - eBay (item 380249230963 end time Aug-06-10 20:53:55 PDT)
5pF 5 pF 100V Radial Silver Dipped Mica Capacitor (25) - eBay (item 380249230963 end time Aug-06-10 20:53:55 PDT)
