PSN-L Email List Message

Subject: Re: Measuring Time Delay
From: GeE777@.......
Date: Sun, 9 Jan 2000 19:50:13 EST

In a message dated 1/9/00 12:42:38 PM Pacific Standard Time, karlc@....... 

  My questions are:
  1.  Given that the instrument probably does not have equal time delay
  response, is there a standardized frequency for which seismometer time
  delay measurements are made?
  2.  If pulse response is used (dropping the object on the floor), can the
  seismometer output just be bandpass filtered to the desired frequency, and
  the delay measured?  If so, what kind of bandpass filtering should be used,
  and should its delay be considered?
  3.  In doing the pulse response measurement, is the proper delay
  measurement made to the first noticable change in the output, or to some
  other point in the output waveform?
  Any help or suggestions are appreciated.
  Karl Cunningham
  La Mesa, CA.
  PSN Station #40

I have invented a device to do just that on a vertical geophone.  I use a DC 
voltage and apply it to the geophone output.  This lifts the coil (or 
depresses it depending on the polarity), then this voltage is switched off 
and the output is connected to an oscilloscope or some othe devicee that can 
immediately measure the coil voltage output as it returns to the normal 
resting place.  One can use this to measure the natural frequency and 
relative amplitude of the geophone.  You can also measure the damping factor. 

George Erich
on the  +  side


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Larry Cochrane <cochrane@..............>