Testing the TK Tar Baby

[picowatt]

chuckle...  I see an analogy for Team Posie here...  It's like getting your learner's permit and getting two hours of driving time under your belt.  The next morning you wake up and say to yourself, "I think I am going to enter a Formula One race today."

TK, your experience with the moving of the probe lead changing the AC peak-to-peak across the CVR and the increased power drain makes my "get conservative" alarm bells start ringing.  What I mean by that is it makes me think that there is a possibility that all measurements are suspect.  I am not saying that they are, just stating that the possibility exists.  Certainly this stuff is beyond the good old "wet the tip of you finger and touch a circuit node to see what happens" trick.  It just goes to show that working in the relatively low frequency range of a 1-2 MHz fundamental is not trivial with a circuit that is switching and has "daddy long legs" wire lead lengths.

If you displace a wire and you observe changes in the scope traces then that tells you that the circuit is "living" in it's immediate ambient environment and the relative permittivity and permeability and conductivity of the immediate 3D surroundings will affect it.  Since we are all bags of salty water we are a "lossy medium" and just standing next to the setup will change its operating frequency and suck some of the energy out of the it because we are shorting out the near-field AC.

Poynt mentioned how sometimes you need a true differential probe which could be placed directly across the CVR, etc, but I know that they are expensive.

The circuit is some kind of quivering and buzzing capacitive-inductive octopus monster that lives in it's near-field radiation environment.  Apparently just waving your hand near the octopus makes it change colour.

It's something we have all seen before I am sure, but it certainly makes it more of a challenge to do measurements

MileHigh

MH,

"Wet the tip of your finger and touch a circuit node to see what happens"

Shocking, just plain shocking...

PW

[TinselKoala]

Yup... I should be able to do the comparison between one battery decoupled with caps and one battery naked.

So this will be done with and without decoupling caps right at the battery, but the battery probe at the board itself?
If I put the battery probe on the battery, then I'll have the issue with probe grounds at different points; if I put the battery probe at the power entry points at the board, then I'll have those long battery leads....
Well, I guess I'll just do it everywhichaway and see what happens.

At this point it looks like the logistics are good to go, anyhow... I mean my car is back together and except for my housemates being in the hospital... all is good for tomorrow's play date.

Meanwhile here's the video of what we've been discussing:

http://www.youtube.com/watch?v=EPESB5-5iTA

[poynt99]

.99,

Dose a similar sim result occur if the entire batt string is decoupled and additional L added to the Batt+ wire to replace batt and interconnect L?

PW

Across the battery/jumper string, or across the entire works including the connecting wires to the apparatus?

In other words, across points 1 & 2, or across points 7 & 3?

[picowatt]

Across the battery/jumper string, or across the entire works including the connecting wires to the apparatus?

In other words, across points 1 & 2, or across points 7 & 3?

.99

Across the entire decoupled battery string with additional L in batt+ wire.

PW

[poynt99]

.99

Across the entire decoupled battery string with additional L in batt+ wire.

PW

So across points 1 & 2, correct?