PSN-L Email List Message
Subject: Re: Seismograph for school
From: "tchannel" tchannel@..............
Date: Tue, 3 Oct 2006 10:28:57 -0600
Hi Bob, I have questions about your great Horz. sensor and the picture.
1. You used solder for the mass, is the mass volume fixed or is there a =
wide range of weights, one could use. I guess the mass is to overcome =
the friction of the hinge and stay stationary. The reason I ask is I =
see a wide range of masses, but most around 5#. What is yours? and what =
is your beam length?
2. Again the solder, is non magnetic is this important as I see many =
things use as mass including iron?
3. I see you used a resistor as a damp, and not a external damper =
device. I have read about doing this, but could not understand the =
values for the resistor. You used 94k (in parallal?) acrossed the coil? =
How did you arrive at that value?
4. You indicate to use a 100k in place of the 10k when using Larry's =
amp, which I will be using. Why is that?
5. The placement of the sensor: Could it be on other than a concrete =
floor, a normal wood floor? Could it be on carpet? I know that is not =
the best choice, but many schools have such floors. Or should one not =
bother with any other surface but a concrete floor?
Thanks for your advise, and "well done!" Ted
----- Original Message -----=20
From: Bobhelenmcclure@..........
To: psn-l@.................
Sent: Sunday, October 01, 2006 7:21 PM
Subject: Re: Seismograph for school
Hi all,
I agree with Chris Chapman on the design of magnets and coils for =
horizontal sensors. Those who have an interest in building their own =
sensors should take a look at mine on John Lahr's web site, especially =
page http://www.jclahr.com/science/psn/mcclure/horiz2.html
I operate three sensors for Z, N, and E. They are adjusted to fairly =
short natural periods, ranging from 5 to 14 seconds. I extend their =
effective period to 24 seconds by a digital filter of my own design, =
with excellent results.
The magnets I recommend are available for $5.50 each, 50mm x 18mm x =
6mm block magnet, from http://www.gaussboys.com You will need four of =
them and two pieces of 1/4 inch flat steel, two inches by three inches, =
and four steel bolts to make a magnet assembly. You do not necessarily =
need separate damping magnets. Just shunt the pickup coil with the =
appropriate resistance.
Bob McClure
Hi Bob, I have questions about your great Horz. sensor and =
the=20
picture.
1. You used solder for the mass, is the mass volume fixed or =
is there=20
a wide range of weights, one could use. I guess the mass is to =
overcome=20
the friction of the hinge and stay stationary. The reason I ask is =
I see a=20
wide range of masses, but most around 5#. What is yours? and what =
is your=20
beam length?
2. Again the solder, is non magnetic is this important as I see =
many things=20
use as mass including iron?
3. I see you used a resistor as a damp, and not a external =
damper=20
device. I have read about doing this, but could not understand the =
values=20
for the resistor. You used 94k (in parallal?) acrossed the =
coil? How=20
did you arrive at that value?
4. You indicate to use a 100k in place of the 10k when using =
Larry's=20
amp, which I will be using. Why is that?
5. The placement of the sensor: Could it be on other =
than a=20
concrete floor, a normal wood floor? Could it be on carpet? =
I know=20
that is not the best choice, but many schools have such floors. Or =
should=20
one not bother with any other surface but a concrete floor?
Thanks for your advise, and "well done!" Ted
----- Original Message -----
Sent: Sunday, October 01, 2006 =
7:21=20
PM
Subject: Re: Seismograph for =
school
Hi all,
I operate three sensors for Z, N, and E. They are adjusted =
to=20
fairly short natural periods, ranging from 5 to 14 seconds. I extend =
their=20
effective period to 24 seconds by a digital filter of my own design, =
with=20
excellent results.
The magnets I recommend are available for $5.50 each, 50mm =
x 18mm=20
x 6mm block magnet, from
http://www.gaussboys.com =
You will=20
need four of them and two pieces of 1/4 inch flat steel, two inches by =
three=20
inches, and four steel bolts to make a magnet assembly. You do not =
necessarily=20
need separate damping magnets. Just shunt the pickup coil with the =
appropriate=20
resistance.
Bob McClure
Locust Valley, NY
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