OT, sorry
I liked Mr. Science, because he has a master's degree- in science.
One of my drinking buddies was a director/producer for Mr. Wizard (Don Herbert). I think the guy is still alive. Since I used to watch him as a kid and I'm 48, Herbert must be pushing Bob Hope's age. I'd love to find his old shows on DVD or tape so that my kid can grow up with the idea of using common stuff to do cool demonstrations. The show did a great job of teaching kids to be creative and resourceful; it was a huge influence on my professional career.
OK, no jokes about going to More Science High. I suppose you graduated from Commie Martyrs.
I liked Mr. Science, because he has a master's degree- in science.
One of my drinking buddies was a director/producer for Mr. Wizard (Don Herbert). I think the guy is still alive. Since I used to watch him as a kid and I'm 48, Herbert must be pushing Bob Hope's age. I'd love to find his old shows on DVD or tape so that my kid can grow up with the idea of using common stuff to do cool demonstrations. The show did a great job of teaching kids to be creative and resourceful; it was a huge influence on my professional career.
OK, no jokes about going to More Science High. I suppose you graduated from Commie Martyrs.
till said:
Try the same thing at 4 meters.
Also, a simple DC measurement isn't a fair comparison. The resistance should be lower using an AC measurement at your power line frequency.
If you have a power transformer handy or better still, a small power amp, you could do an easy AC measurement. Use something like a 100 ohm resistor (so you don't load down the transformer or the amp to any degree) in series with the output.
First, take an AC voltage measurement with the 100 ohm resistor across the output of the transformer or amp. Then tie one side of the secondary (or the ground on the power amp) to one grounding rod and the other side through the 100 ohm resistor to the other grounding rod and take a second measurement across the 100 ohm resistor.
Then you can calculate the impedance between your grounding rods.
se
It would be interesting to see if AC actually does give any lower reading. From what I understand, DC readings can be higher because of the nature of the charge carriers (ions), which get diffusion-limited via formation of a double-layer at the electrode surfaces. But the current from an ohmmeter is so low that I'd guess that the diffusion limitation wouldn't be significant. Experiment tells all, though.
At the begining of the thread the question was about center tap wire of the tranformer connected to ground. According to me this wire is used only to carry the unbalance current betwen positve supply an negative supply, if both current are perfectly equal ( including capacitor leakage )there will be no current in that path and you could remove it (cut the wire ).This is wy in some case it maques no difference an in some other case there is a difference. For a power amplifier in fact it could be used to make some protection to protect the speaker in case of a power transistor short cicuit. If by any chance you have QUAD 606 schematic have a look and you will find an application of a similar technique.
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