Chris
I had thought of a piezo in the past but got confused with it's output. I b=
elieve it measures the rate of change of movement of the sensor. Since an a=
ccelerometer gives acceleration results when measuring deflection, Does one=
 have to integrate piezo output results to get acceleration?
Regards
Barry

--- On Thu, 11/12/09, ChrisAtUpw@.......  wrote:

From: ChrisAtUpw@....... 
Subject: Re: WinQuake Times
To: psn-l@..............
Date: Thursday, November 12, 2009, 5:11 PM

=0A=0A =0A=0A=0AIn a message dated 12/11/2009, barry_lotz@............. wri=
tes:=0AI found a =0A  company called Sensr that sells 3 different data acqu=
isition systems for $700 =0A  up. Not really that bad when it includes a 3 =
axis and =0A  storage.
=A0http://www.sensr.com/products/civil-and-structural/
Regards
Barry
=0A=0AHi Barry,=0A=A0=0A=A0=A0=A0=A0These are commercial MEMs units with a =
range of 12 =0Ag to 0.05 g and 0.001 g resolution. These are fine for makin=
g environmental =0Ameasurements on bridges, buildings, etc., but you need t=
o be able to measure to =0Amicro g levels for a strong motion seismometer, =
whether professional or amateur. =0A=0A=A0=A0=A0=A0Larry sells a 3 axis str=
ong motion accelerometer =0Aboard with serial amplifiers giving=A0ranges of=
 2 g and 70 milli g maximum, =0Adriving a 16 bit ADC. These give 6-9 mV / g=
 and 1 micro V p-p noise.=0A=A0=A0=A0=A0The ADXL103/203 have=A0a range of +=
/-1.7 g and a =0Anoise level of 110 micro g / root Hz rms. For 20 Hz bandwi=
dth the noise is about =0A0.7 milli g pk. You are relatively unlikely to ob=
serve quakes with these unless =0Ayou live over an area of known seismic ac=
tivity.=A0=A0=0A=A0=A0=A0=A0Colibrys http://www.colibrys.com/e/page/140/=A0=
offer =0Aa +/3 g range and 300 nano g rms / root Hz noise. However, Avnet s=
eem to have an =0Aunrealistic idea of the value of this sensor. I note that=
 they are not stocking =0Athem at the moment.=0A=A0=A0=A0=A0I have used pie=
zo disks from www.digikey.com 102-1170-ND at $1.62 and =0A668-1190-ND at $2=
..72 as accelerometers. Used in simple bending mode supported on =0Atwo side=
s (NOT as a circular diaphragm),=A0 with a central 1 oz mass on a =0Asquare=
 brass tube support=A0(http://www.ksmetals.com/) and=A0a FET =0Ainput ampli=
fier, they can sense right down to the seismic background noise =0Alevel. T=
hey need to be kept dry at all times and temperature variations need to =0A=
be reduced as far as possible.=A0 I mount one with the amplifier in a glass=
 =0Ajam=A0jar with a rubber seal metal lid and use a disk of circuit board =
with =0Afeed through soldered pins. There is a lot more information availab=
le at http://jclahr.com/science/psn/chapman/piezo/index.html=0A=A0=A0=A0=A0=
You may feel quakes over about 0.015 g.=0A=A0=0A=A0=A0=A0=A0Regards,=0A=A0=
Chris
I had thought of a piezo in the past=
 but got confused with it's output. I believe it measures the rate of chang=
e of movement of the sensor. Since an accelerometer gives acceleration resu=
lts when measuring deflection, Does one have to integrate piezo output resu=
lts to get acceleration?
Regards
Barry

--- On Thu, 11/12/09=
, ChrisAtUpw@....... <ChrisAtUpw@.......> wrote:

From: ChrisAtUpw@....... <ChrisAtUpw@.......><=
br>Subject: Re: WinQuake Times
To: psn-l@..............
Date: Thursda=
y, November 12, 2009, 5:11 PM

=0A=0A =0A=0A=0A
In a message dated 12/11/2009, barry_lotz@............. writes:=0A
I found a =0A  company called Sensr that sells 3 di=
fferent data acquisition systems for $700 =0A  up. Not really that bad when=
 it includes a 3 axis and =0A  storage.
 http://www.sensr.com/produ=
cts/civil-and-structural/
Regards
Barry
=
=0A
=0A
Hi Barry,
=0A
 
=0A
 &nbs=
p;  These are commercial MEMs units with a range of 12 =0Ag to 0.=
05 g and 0.001 g resolution. These are fine for making environmental =0Amea=
surements on bridges, buildings, etc., but you need to be able to measure t=
o =0Amicro g levels for a strong motion seismometer, whether professional o=
r amateur. =0A
=0A
    Larry sells a 3 axis st=
rong motion accelerometer =0Aboard with serial amplifiers giving range=
s of 2 g and 70 milli g maximum, =0Adriving a 16 bit ADC. These give 6-9 mV=
 / g and 1 micro V p-p noise.
=0A
    The ADXL=
103/203 have a range of +/-1.7 g and a =0Anoise level of 110 micro g /=
 root Hz rms. For 20 Hz bandwidth the noise is about =0A0.7 milli g pk. You=
 are relatively unlikely to observe quakes with these unless =0Ayou live ov=
er an area of known seismic activity.  
=0A
  =
  Colibrys http://www.colibrys.com/e/page/140/ o=
ffer =0Aa +/3 g range and 300 nano g rms / root Hz noise. However, Avnet se=
em to have an =0Aunrealistic idea of the value of this sensor. I note that =
they are not stocking =0Athem at the moment.
=0A
   =
; I have used piezo disks from www.digikey.com 102-1170-ND at $1.62 and=
 =0A668-1190-ND at $2.72 as accelerometers. Used in simple bending mode sup=
ported on =0Atwo sides (NOT as a circular diaphragm),  with a central =
1 oz mass on a =0Asquare brass tube support (http://www.ksmetals.com/=
) and a FET =0Ainput amplifier, they can sense right down to the seism=
ic background noise =0Alevel. They need to be kept dry at all times and tem=
perature variations need to =0Abe reduced as far as possible.  I mount=
 one with the amplifier in a glass =0Ajam jar with a rubber seal metal=
 lid and use a disk of circuit board with =0Afeed through soldered pins. Th=
ere is a lot more information available at http:=
//jclahr.com/science/psn/chapman/piezo/index.html
=0A
 &n=
bsp;  You may feel quakes over about 0.015 g.
=0A
 =
=0A
    Regards,
=0A
 
=0A=
    Chris Chapman
<=

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