You been in my toolbox again !
That's not my soldering iron though, that's my colonic pile popper .. .. you need to put that back where I'd like to put it !!
I think the original schematic is flawed in several ways.
1) TL084 & BC557 transistor selection and slew rate problems resulting in a partial sine instead of a pulse. Slew rate is reduced such that the pulse is 22% of a sine instead of 50% of a square wave.
It should be a current source pulse such that output voltage is proportional to ESR.
Try reducing 100kHZ towards 10kHz with a larger cap. for C3 1nF-> 10nF then recapture waveforms until a better driver is found. It would be slightly better to bypass the transistor all together and drive the TL084 direct to bridge. with +4V to 0.5K load for 8mA using a bipolar signal around Virt. Gnd rather than a unipolar pulse with DC above Virtual ground.
We have a cap manufacturer on the board :O, I got a dislike on my post ROFLMAO. My LCR meter gives you a choice of frequency and the results can be different from the same cap depending on frequency, but so far all the sheets I have looked at say 100kH with a couple using 10kH.
But like you say if they are out its normally way off not just a little bit.
Based on other circuits found while surfing, the intent might be for an intentionally slew-rate limited or R-C risetime limited square wave to approximate a sine wave. Not a great approximation for sure, but better than nuttin. Still, I vote for adding a true sine wave oscillator section. A phase-shift osc would have way lower high freq harmonics and good-enough amplitude stability without all of that Wein-ing.
Oooh... another chance for me to plug one of my favourate circuits?
Perhaps the circuit I use here would be of use - a two transistor phase-shift oscillator with Wien-bridge style amplitude control. It gives THD around 1% is seem to remember.
Thank you very much for your suggested circuit as an alternative method I could use to lose the will to live !
I feel certain that if I ever were to need a circuit to oscillate my navel, this would be the one I would chose, for sure. I marvel at the notion that such a circuit would have the power to efficiently move the bulk that surrounds my navel sufficiently to cause an oscillation and feel sure if it were achieved it would be a sore wave for sure .. .. ..
Oooh... another chance for me to plug one of my favourate circuits?
Perhaps the circuit I use here would be of use - a two transistor phase-shift oscillator with Wien-bridge style amplitude control. It gives THD around 1% is seem to remember.
I've been reading through your ESR meter posted detail .. .. can't see any problem, as you say, much more straightforward.
Are you aware there has been a revised version published in 2004 ? Some variations ... .. some of the obsolete components have been upgraded; only one battery used;
Basically, looks the same to me .. .. any comments ?
I've been reading through your ESR meter posted detail .. .. can't see any problem, as you say, much more straightforward.
Are you aware there has been a revised version published in 2004 ? Some variations ... .. some of the obsolete components have been upgraded; only one battery used;
Basically, looks the same to me .. .. any comments ?
Firstly, thank you for going to the trouble of producing this PCB .. .. ..
Unfortunately, at this moment in time I don't have the means to produce a custom PCB .. I tried etching once .. .. never, ever again .. I got into such a mess .. .. ... I have a small CNC machine planned and partly manufactured for the purpose, but I'm a way off completion . I have the x axis bed complete and I'm currently working on the gantry, but there's a lot of work to do yet.
Maybe some of the other members will be in a position to make use of your plan immediately .. but I will keep it in store to try out my machine in the future.