Mike:
Have a look at my web site (http://www.bryantlabs.net/VertSeis.html) for =
some information on my version of the STM-8.
The first thing to remember is that it appears that Sean-Thomas used =
some electronics modules that he had in his lab for some of the =
functions. They have features and parts that may not be used in the =
STM-8. I think he also left many details out, "as an exercise for the =
student"
With that said, here's what I think the answers to you questions are:
1) The 10K resistor into A2 connects to the sine wave oscillator =
output. In another drawing called "Bridge connection of the VRDT....", =
he shows it connected to the phase 2 output of the oscillator =
transformer, the signal called "Reference to Demod." in the upper right.
2) He doesn't call this out explicitly, but I believe that the 10K =
resistor into A3 should connect to the other output phase from the =
oscillator transformer. To make the circuit work right, you might have =
to swap these two connections, depending on signal phases through the =
system.
3) Those blocks refer to some circuitry shown at the bottom of another =
drawing called "Block Diagram of Hardware Store Broadband Seismometer":
"Displacement Xducer Gain Amp and Filter 5X to 20X gain?" refers to A1 =
and it's related parts in the lower left.
"Integrator, Unity Gain Instrumentation Amp 20 to 200 Seconds?" refers =
to A2 and it's related parts in the lower middle.
"VBB Output Amplifier and Low Pass Filter Gains 2X to 20X?" are not =
detailed anywhere that I know of. I assumed a simple op-amp stage with =
a low pass filter at around 100 Hz to remove unwanted noise.
The schematics on my web pages make an attempt to pull all of those =
drawings together, with some changes made to use some suitable parts I =
had on-hand, and because no engineer can ever leave well enough alone...
=20
Good luck!
Keith
----- Original Message -----=20
From: Mike Speed=20
To: PSN-L@.................
Sent: Wednesday, December 24, 2003 7:21 AM
Subject: STM-8 Questions
I would like to build the STM-8 as close to what Sean had as possible =
and I have the following questions on the STM-8:
On the schematic entitled, "Tiltmeter (and VRDT) Bridge =
Amplifier/Demodulator/Filter/DC Amplifier" (Rev 10/20/98):
1) To what does the 10K resistor on the inverting input of A2 connect =
(6)?
2) To what does the 10K resistor on the inverting input of A3 connect =
(7)?
On the "Block Diagram of the Electonics for the Leaf Spring Broadband =
Seismometer..." sheet (Rev: 25 Jan 98):
1) What is the schematic of the "Displacement Xducer Gain Amp and =
Filter 5X to 20X gain?"
2) What is the schematic of the "Integrator, Unity Gain =
Instrumentation Amp 20 to 200 Seconds?"
3) What is the schematic of the "VBB Output Amplifier and Low Pass =
Filter Gains 2X to 20X?"
Thank you,
Greg L. Sharp
mike8s2(at)hotmail.com
-------------------------------------------------------------------------=
-----
Do you Yahoo!?
Mike:
Have a look at my web site (http://www.bryantlabs.ne=
t/VertSeis.html)=20
for some information on my version of the STM-8.
The first thing to remember is that it =
appears that=20
Sean-Thomas used some electronics modules that he had in his lab for =
some of the=20
functions. They have features and parts that may not be used in =
the=20
STM-8. I think he also left many details out, "as an exercise for =
the=20
student"
With that said, here's what I think the =
answers to=20
you questions are:
1) The 10K resistor into A2 =
connects to the=20
sine wave oscillator output. In another drawing called "Bridge =
connection=20
of the VRDT....", he shows it connected to the phase 2 output of the =
oscillator=20
transformer, the signal called "Reference to Demod." in the upper=20
right.
2) He doesn't call this out =
explicitly, but I=20
believe that the 10K resistor into A3 should connect to the other output =
phase=20
from the oscillator transformer. To make the circuit work right, =
you might=20
have to swap these two connections, depending on signal phases through =
the=20
system.
3) Those blocks refer to some =
circuitry shown=20
at the bottom of another drawing called "Block Diagram of Hardware Store =
Broadband Seismometer":
"Displacement Xducer Gain Amp and Filter 5X to 20X gain?" refers =
to A1=20
and it's related parts in the lower left.
"Integrator, Unity Gain Instrumentation Amp 20 to 200 Seconds?" =
refers to=20
A2 and it's related parts in the lower middle.
"VBB Output Amplifier and Low Pass Filter Gains 2X to 20X?" are =
not=20
detailed anywhere that I know of. I assumed a simple op-amp =
stage with a=20
low pass filter at around 100 Hz to remove unwanted =
noise.
The schematics on my web =
pages make an=20
attempt to pull all of those drawings together, with some changes made =
to use=20
some suitable parts I had on-hand, and because no engineer can ever =
leave well=20
enough alone...
Good luck!
Keith
----- Original Message -----
From:=20
Mike =
Speed=20
Sent: Wednesday, December 24, =
2003 7:21=20
AM
Subject: STM-8 Questions
I would like to build the STM-8 as close to what Sean had as =
possible and=20
I have the following questions on the STM-8:
On the schematic entitled, "Tiltmeter (and VRDT) Bridge=20
Amplifier/Demodulator/Filter/DC Amplifier" (Rev 10/20/98):
1) To what does the 10K resistor on the inverting input of =
A2=20
connect (6)?
2) To what does the =
10K resistor=20
on the inverting input of A3 connect (7)?
On the "Block Diagram of the Electonics for the Leaf Spring =
Broadband=20
Seismometer..." sheet (Rev: 25 Jan 98):
1) What is the schematic of the "Displacement Xducer Gain Amp and =
Filter=20
5X to 20X gain?"
2) What is the schematic of the "Integrator, =
Unity=20
Gain Instrumentation Amp 20 to 200 Seconds?"
3) What is the =
schematic=20
of the "VBB Output Amplifier and Low Pass Filter Gains 2X to =
20X?"
Thank you,
Greg L. Sharp
mike8s2(at)hotmail.com
Do you Yahoo!?
Yahoo! Photos - Get=20
your photo on the big screen in Times =
Square