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Geophone Amplifier

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sonicj:
I'm attempting to construct a geophone amplifier and, as i normally do, neglected to pay attention to the resistor values when placing my parts order as i thought i had a pretty comprehensive collection of standard values on hand... out of the values listed, i think i had only one or two in my bins. this is the first application example i've seen with such uncommon values... is it that this is a highly tuned example circuit and requires this sort of precision to function? or are the values given a best of whats commercially available and can be replaced with closest values on hand? is there a downside to replacing some of the resistors with precision pots?

also, in the formula at the bottom, what do the two || represent?

cheers!
-sj

EEVblog:
The values don't look to be critical.

The || is a standard symbol meaning parallel (the standard parallel resistance formula)

Dave.

Zero999:
The resistor values are standard E96 values, not as common as E24 but available from most suppliers.

You can make any E96 value to within 0.17% accuracy from any two E24 values connected in series or parallel. Attached is a table I use which makes it easier to work out. As you can see there are some duplicates to give yuou a choice between more convenient values and higher accuracy.

sonicj:

--- Quote from: EEVblog on December 31, 2010, 02:59:48 am ---The values don't look to be critical.

The || is a standard symbol meaning parallel (the standard parallel resistance formula)

Dave.

--- End quote ---
thanx dave!

anyone happen to know this one? [size=14]?[/size]


--- Quote from: Hero999 on December 31, 2010, 08:58:46 am ---The resistor values are standard E96 values, not as common as E24 but available from most suppliers.

You can make any E96 value to within 0.17% accuracy from any two E24 values connected in series or parallel. Attached is a table I use which makes it easier to work out. As you can see there are some duplicates to give yuou a choice between more convenient values and higher accuracy.



--- End quote ---
thanx hero! the chart is super helpful! i stumbled onto a few combinations on my own, but the light bulb never clicked that i could make all of the values... good stuff!


unfortunately, i have some bad news to report on the geophone endeavor. there will be no earthquake detection at my house tonight as i let the smoke out of one of the resistors. i don't think it had anything to do with the values, more due to mild dyslexia + working with double sided protoboard.  :-\   i might be better off just starting over with everything on one side as debugging this double sided board gets confusing with the quickness!
-sj

Bored@Work:

--- Quote from: sonicj on January 01, 2011, 01:59:06 am ---anyone happen to know this one? ?
--- End quote ---

Congruent to or isomorphic to. Don't you kids learn that in school any more?

But ok, datasheet authors also don't learn that in school any more, because  ? is frequently mistaken for  ?. The later also means isomorphic to, but also approximately equal. And it is usually approximately equal what they mean when wrongly using the ?.

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