Thank you much sismos/Angel,

More questions to ask.

The specs for my geophone is like an ideal 2.99V/IN/SEC
Is that like ( 117.7V/M/sec) or (1.177V/cm/SEC).
[which seems more like 1.5V/IN/SEC when I look at it myself]
through the filtered electronics. Then I amplify like X1025 (60Dbv)
Then into a 12bit A/D running at +/- 2.045 Volts.
This means about 1023 count == output of 1.023Volts
Which is (0.001V/count)/1025 or 0.975 microvolts per count
on the geophone output which is possibly 114.7micrometers/sec of motion ?
Is this the kind of information they want ?

The order goes something like this:
1. Geophone input:   1uM/sec
2. Geophone output: 117.7 uV
3. Amplifier Input:      117.7 uV
4. Amplifier Output:  120.7 mV
5. Counts out of A/D: +120
Does any of this sound right ?
Does this come anywhere close to calibration ideas ?

The only way I know how to calibrate or evaluate the
sensitivity is to go to the USGS website for
Theoretical values relating to a specific EQ then
translating the numbers backward through the system
to match the theoretical intensity of the EQ
as it passed through my system at my location.
Might this be a proper way to look at my
own system ??

Right now for regional quakes Winquake gives me a very good idea
of the actual Ml (Richter magnitude). Might I
use the correctional numbers for Winquake to
enhance the accuracy and precision of my sensor.
What I really mean is this, if I can achieve zero correction
for correct ML readings, then my calibration numbers must be right ?
Then I may send this number to IRIS with my data ??

Do I need to bandpass filter the read data at 1Hz before applying the numbers
to the data since the USGS states these numbers to be at 1Hz?

Best regards,
geoff

----- Original Message ----- 
From: "sismos" 
To: 
Sent: Friday, April 09, 2010 7:46 PM
Subject: Re: Question to Techno-Philes


> Hi Geoff,
> 
> I have to admit you're a tough one.
> 
> 
> About metrology;
> 
> Calibrating a thermometer to an accuracy of +/- 1 degree so you can
> measure the temp of baby formula can be done in most any kitchen and no
> one can argue that it is not calibrated. 
> 
> Calibrating seismographs is much the same, it just does not have to be
> that accurate. A few parts per thousand is good enough and that is
> within the reach most anyone that can build a home seismometer.  I was
> calibrating a sensor during a class and sweating the decimals and the
> instructor said to calm down, +/- 5% was fine.
> 
> He asked me to image setting off a firecracker at one end of a pile of
> construction ruble and sensing it at the other end with a very accurate
> sensor and one that was not so accurate and trying to say much about the
> pile of ruble or nature of the firecracker with either sensor.
> 
> About amateurs;
> 
> Being an amateur has very little if anything to do with the quality of
> what is being done. In it's simplest context it just means you don't get
> paid for doing what you do. Many amateur do great work and in some cases
> better work than paid professional.  Paid professional and scientist
> have to be concerned about the bottom line and us amateurs can ignore
> that reality.  I think you would be surprised that many amateurs are
> building seismometers that are just as good as what the professionals
> build, and better than some, and I will add if you can calibrate and
> keep the temperature constant then the data from any seismometer is good
> data. 
> 
> About IRIS
> 
> Yes, you can send raw data to IRIS along with the calibration file and
> they will make a power density function display for you, but you will
> need the calibration file.  IRIS knows nothing about your seismometer
> and the calibration file allows them not to care.  That's what the
> calibration file is about, not caring about the sensor and it's
> associated electronics.
> 
> Geoff, I have no doubts that calibrating a seismograph is well within
> your abilities.  I will add that if all you care about is picking phases
> (P and S and their variants) then calibration is not an issue.  And for
> small local earthquakes you can use the duration or coda to determine
> magnitude (Mc or Md) so you have no need for calibration, it does not
> matter.  And if you had a bunch of sensors like that and some decent
> timestamping of the data then you could locate epicenters.  
> 
> Regards,
> 
> Angel
> 
> 
> 
> 
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