In a message dated 28/12/2009, barry_lotz@............. writes:
Chris
" Chris
I found the abstract and filter diagram on John Lahr's web site. 1) I am
not sure how the max gain is chosen. Is it based on the difference between
the actual sensor low frequency corner and the desired low frequency
corner given a 40 db /decade dropoff?
Hi Barry,
If you wished to get 20 seconds from a 1.5 second pendulum, you would
need a total gain at 20 seconds of 178. Each stage will need a gain of 13.3
2) I assume the two single pole circuits identical
That is correct
3) Do the other values in the example circuit remain the same except as
you have commented on?
Correct.
4) If I want a lower corner frequency of 0.03 hz is the "lower turnover
frequency (1/2 Pi C1 R2)" = 0.015 hz? It is probably obvious I don't have
the full report."
See above. correct
I realize that R3,R7 & R11 are offset resistors.
Correct
R5 = R6 = R8 = R9
R10 may be chosen to give any gain that you need. I use a gain of at least
x2 per stage
How does one determine the value of R5 and R8 or does it matter?
I choose values of about 20 K. You don't want to overload your
amplifier, but you want to use values which have low noise. 150 K is too much in
my opinion.
This will give a high maximum gain and noise below 0.03 Hz, so you
couple the circuits with a 2 pole high pass filter set at about 0.015 Hz.
Regards,
Chris Chapman
In a message dated 28/12/2009, barry_lotz@............. writes:
Chris
" =20
Chris
I found=
the=20
abstract and filter diagram on John Lahr's web site. 1) I am not=
sure=20
how the max gain is chosen. Is it based on the difference be=
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the actual sensor low frequency corner and the desired low frequen=
cy=20
corner given a 40 db /decade dropoff?
Hi Barry,
=
;If you=20
wished to get 20 seconds from a 1.5 second pendulum, you would nee=
d a=20
total gain at 20 seconds of 178. Each stage will need a gain of=20
13.3
2) I assume the=
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single pole circuits identical
=
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correct
3) Do the other=
values in=20
the example circuit remain the same except as you have commented=
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on?
Correct.
4) If I want a lo=
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corner frequency of 0.03 hz is the "lower turnover frequency (1/2=
Pi C1=20
R2)" =3D 0.015 hz? It is probably obvious I don't have the full=20
report."
See above. =20
correct
I realize that R3,R7=
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R11 are offset resistors.
Correct
R5 =3D R6 =3D R8 =3D R9
R10 may be chosen to give any gain that you need. I use a gai=
n of=20
at least x2 per stage
How does one determine the value of R5 and R8 or does it=20
matter?