Hi Willen,I am curious: Why touching the high impedance audio input (specially floating input) cause horrible output? What kind of signal out body have to cause such output?
On a similar vein, if you connect the tip of a scope probe to the earth wire of a scope probe, you can still see a signal on the scope if you turn the gain up.Notice that I am not actually touching the resistor, just moving my finger nearby was enough to see a voltage. Remember ohms law, E=IR, so with R = 1Megohm does not take much I to develop a potential. Keep this in mind when making measurement of High Z circuits
I don't know if Ian Rogers mentioned it, but JimB certainly did, here:I think Ian Rogers mentioned this technique on another thread, but I cant find it now.
If you practice Yoga and are able to stand on your head, then the rest of your body would form a quarter wavelength radiator which could significantly enhance your transmitting gain.So if I wear an aluminum hat over my head, would it help the noise reduction or make it worse?
I am sorry for not being more specific. I was talking about the noises in my head!
If you practice Yoga and are able to stand on your head, then the rest of your body would form a quarter wavelength radiator which could significantly enhance your transmitting gain.
Sorry JB- yes it was you.I don't know if Ian Rogers mentioned it, but JimB certainly did, here:
They work quite well, I have used one a few times recently when looking at high frequency signals.
Hi MB,I only had mentioned this because I was measuring the resistance of a high ohmic value resistor, and I noticed how the lower ordered digits bobbled around. As an experiment I put the resistor in a metal box (see first post), and by doing so the reading settled out. So it was just an observation.
I was trying to think where one might use such high value resistors and at the moment I cant really think of any, but let's say you need an amp with a gain of 1 million for example. One might be quick to take an op amp and use the Av=RF/RI thus grabbing one big resistor for RF, but knowing what we know about the possible noise of a large ohmic resistor might instead go for a 2 stage op amp with each one having a gain of 1000, thus reducing the noise contribution associated with very large ohmic resistors. According to my spell check ohmic is not a word, hmm...
The noise issue associated with large resistance is discussed in the low level measurement handbook. I will see if I can round up the link.
RIP Bob Pease,Funny you should mention the 555 Spec, at my last job we were forbidden from using the part (At the time, did not know why only it was off-limits). Anyways I been reading a lot of old articles from Analog Jedi Bob Pease, I came across this bit where Mr. Pease gives his opinion on the ubiquitous 555.
Quoted from Source: http://electronicdesign.com/analog/what-s-all-555-timer-stuff-anyway
Pease replied in his characteristically straightforward way. He noted:
“Hi, Jeff H., I have almost never used a 555. Maybe never? I use op-amps, LM324's, LM311's, LF356's. I use 74HC04's and 74C14's but not 555's. I've used ECL fast logic, and discrete transistors. But the 555 just does not do anything precise, or even semi-precise, that I need done. So that's one thing I can "share" - my favorite circuit to use a 555, is: a blank piece of paper. Never touch the things. Go ahead and print that. / rap”