[ANSS-netops] ANSS-netops Digest, Vol 47, Issue 1

Tue Jun 11 13:28:30 UTC 2013

John,
setting up a digitizer with a source that can theoretically produce an 
infinite output voltage poses some interesting problems. First the 
digitizer has over voltage protection on the input, and even though a 
seismometer operating under strong excitation may produce several 
hundred volts, it is not capable of supplying much current, so this 
should not be a problem.

  A typical short period monitoring system is set up to produce a preamp 
out signal of 10mVp-p with a preamp gain of 72dB in a quiet site typical 
of east TN or western NC. This signal typically had a bandwidth of 
approximately 25 Hz. a digitizer operating at 100SPS has a bandwidth of 
approximately 40Hz at the cutoff frequency of the anti alias filter. The 
wider bandwidth will produce a little more noise because of all the 
cultural source noise at the higher frequencies. Adjusting for the 
bandwidth, i would expect the noise to be around 15mVp-p at a gain of 72 
dB. 72 dB is a gain of approximately 4000. if you divide 15mV by 4000 
you come up with a seismometer signal of 3.75uVp-p. this is the signal 
you will be digitizing.

  Now lets look at the digitizer. for a true 24 bit digitizer there are 
2**24 bits or roughly 16.8 million counts . If you take the largest full 
scale range of the digitizer to be 40Vp-p this would mean that 1 count 
represents a p-p signal of 2.38uVp-p. This would mean that the output of 
a non amplified seismometer would be 1.5 counts at normal background. 
Here in lies the crux of the problem. the output of a seismometer 
increases with excitation frequency implying that at low frequencies 
there would be even less output. One way around this is to set the 
digitizer gain higher by setting its full scale value to a lower value. 
if you use a full scale value of 5vp-p, 1 count now represents 1/8 of 
what it did at 40 Vp-p. or approximately 300nV. this would in turn give 
you about 8-10 counts of digitized signal at normal background levels.

A typical S-13 seismometer is assumed to have a dynamic range of 
approximately 130 dB. while a 24 bit digitizer has a theoretical dynamic 
range of 144 db. setting the digitizer to higher gain of 10 Vp-p would 
therefore match the theoretical dynamic range of the sensor closer to 
the dynamic range of the digitizer. Personally I would like to see 
background counts from the digitizer in the range of 500 to 1000 counts 
typically so that loss of low frequency signals is not so apparent. 
unfortunately, this can only be obtained with an outboard amplifer and 
will necessarily sacrifice some of the available dynamic range of the 
sensor. All of the above calculations assume a white distribution of 
noise in the digitizer(probably a good assumption with a high quality 
digitizer) and lack of local high frequency noise sources(turbulent 
water flow, highway, mechanical equipment...) near the seismometer. Hope 
this helps provide at least a rudimentary framework for analyzing the 
problem.
Greg steiner
On 6/11/2013 7:00 AM, anss-netops-request at geohazards.usgs.gov wrote:
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> Today's Topics:
>
>     1. Configuration for Kinemetrics Basalt - S-13s
>        (John H Parker (jhparkr1))
>     2. Re: Configuration for Kinemetrics Basalt - S-13s (Jacob Crummey)
>     3. Re: Configuration for Kinemetrics Basalt - S-13s
>        (Jaffet Martinez Pagan)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 10 Jun 2013 19:11:16 +0000
> From: "John H Parker (jhparkr1)" <jhparkr1 at memphis.edu>
> To: "anss-netops at geohazards.usgs.gov"
> 	<anss-netops at geohazards.usgs.gov>
> Subject: [ANSS-netops] Configuration for Kinemetrics Basalt - S-13s
> Message-ID:
> 	<4F38B6967992AD44A2D7F6E812E6A1B5298E4FD4 at BLUPRD0412MB595.namprd04.prod.outlook.com>
> 	
> Content-Type: text/plain; charset="us-ascii"
>
> Net-Ops mailing list:
>
> We are going to be setting up two new stations using Kinemetrics Basalt DASs with S-13 sensors. We have never done this before, and wondered if anybody out there had done this and how you had configured it.
>
> Thanks so much for your help,
> John
>
> John H. Parker
> Research Associate/Technician
> The University of Memphis
> Center for Earthquake Research and Information (CERI)
> jhparkr1 at memphis.edu<mailto:jhparkr1 at memphis.edu>
> (336) 228-7230
> (901) 258-5115 (Mobile)
>
> The University of Memphis, a Tennessee Board of Regents institution, is an Equal Opportunity/Affirmative Action University. It is committed to education of a non-racially identifiable student body.
>
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> ------------------------------
>
> Message: 2
> Date: Mon, 10 Jun 2013 12:16:36 -0700
> From: Jacob Crummey <jcrummey at gps.caltech.edu>
> To: anss-netops at geohazards.usgs.gov
> Subject: Re: [ANSS-netops] Configuration for Kinemetrics Basalt -
> 	S-13s
> Message-ID: <51B62614.1040407 at gps.caltech.edu>
> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
>
> Hi John,
>
> Are you looking for the configuration of the Basalt specific to the S-13
> sensors?  Or are you asking for help in setting up a Basalt in general?
>
> I can help you with setting up a Basalt, but we don't use the S-13
> sensors in our network.
>
> -Jacob
>
>
> On 06/10/2013 12:11 PM, John H Parker (jhparkr1) wrote:
>> Net-Ops mailing list:
>>
>> We are going to be setting up two new stations using Kinemetrics
>> Basalt DASs with S-13 sensors. We have never done this before, and
>> wondered if anybody out there had done this and how you had configured
>> it.
>>
>> Thanks so much for your help,
>>
>> John
>>
>> John H. Parker
>>
>> Research Associate/Technician
>>
>> The University of Memphis
>>
>> Center for Earthquake Research and Information (CERI)
>>
>> jhparkr1 at memphis.edu <mailto:jhparkr1 at memphis.edu>
>>
>> (336) 228-7230
>>
>> (901) 258-5115 (Mobile)
>>
>> The University of Memphis, a Tennessee Board of Regents institution,
>> is an Equal Opportunity/Affirmative Action University. It is committed
>> to education of a non-racially identifiable student body.
>>
>>
>>
>> _______________________________________________
>> ANSS-netops mailing list
>> ANSS-netops at geohazards.usgs.gov
>> https://geohazards.usgs.gov/mailman/listinfo/anss-netops
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> ------------------------------
>
> Message: 3
> Date: Mon, 10 Jun 2013 16:30:33 -0400
> From: Jaffet Martinez Pagan <jaffet.martinez at upr.edu>
> To: Jacob Crummey <jcrummey at gps.caltech.edu>
> Cc: anss-netops at geohazards.usgs.gov
> Subject: Re: [ANSS-netops] Configuration for Kinemetrics Basalt -
> 	S-13s
> Message-ID:
> 	<CAH4w05As5cUQNv3OHVeD6OWpp1QC3uT9PO47NsMAOL0Bk1vuZw at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi John:
> Please visit the kinemetrics website. They have technicals reports to how
> configure the basalts units. Go to Application notes, you need a password,
> and then go to Rock Family sections and then Rock Training Resources. If
> you need a password ask for one.
>
>
> 2013/6/10 Jacob Crummey <jcrummey at gps.caltech.edu>
>
>>   Hi John,
>>
>> Are you looking for the configuration of the Basalt specific to the S-13
>> sensors?  Or are you asking for help in setting up a Basalt in general?
>>
>> I can help you with setting up a Basalt, but we don't use the S-13 sensors
>> in our network.
>>
>> -Jacob
>>
>>
>>
>> On 06/10/2013 12:11 PM, John H Parker (jhparkr1) wrote:
>>
>>   Net-Ops mailing list:****
>>
>> ** **
>>
>> We are going to be setting up two new stations using Kinemetrics Basalt
>> DASs with S-13 sensors. We have never done this before, and wondered if
>> anybody out there had done this and how you had configured it. ****
>>
>> ** **
>>
>> Thanks so much for your help,****
>>
>> John****
>>
>> ** **
>>
>> John H. Parker****
>>
>> Research Associate/Technician****
>>
>> The University of Memphis****
>>
>> Center for Earthquake Research and Information (CERI)****
>>
>> jhparkr1 at memphis.edu****
>>
>> (336) 228-7230****
>>
>> (901) 258-5115 (Mobile)****
>>
>> ** **
>>
>> The University of Memphis, a Tennessee Board of Regents institution, is an
>> Equal Opportunity/Affirmative Action University. It is committed to
>> education of a non-racially identifiable student body.****
>>
>> ** **
>>
>>
>> _______________________________________________
>> ANSS-netops mailing listANSS-netops at geohazards.usgs.govhttps://geohazards.usgs.gov/mailman/listinfo/anss-netops
>>
>>
>>
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>

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