Seismology Instruction with the AS 1

Gain  This setting adjusts the amplifi cation of the signal and varies with the location 

of the seismometer.  Choose a gain setting such that the background noise is just 

visible.  For example, there is always a little bit of up and down movement of the 

trace.  A value between 25 50 is ideal.  If the trace is too noisy, adjust the gain 

to a lower value.  Any adjustment to the gain may require slight adjustments to the 

set zero level.

Low pass fi lter cutoff  Set to 1 Hz.  This setting fi lters out local noise from the 

school building and makes it easier to see distant earthquakes.

Days to retain records  This setting controls how many days are available to scroll 

back through when looking for events.  All data will be stored by the system until it is 

deleted by the user, this setting just controls how much is available to display.

   Decimate Factor  This setting controls the number of plotted points when the trace 

is redrawn, but does not affect the quality of the recording.  Set the decimate factor to  

            10.  If scrolling is very slow, adjust this setting higher to speed up scrolling.

Finding the Trace

   From the File Menu choose Settings > Set Zero Level

   Set the Zero Level at 2048 (This value centers the trace 

thus preventing clipping of the signal from a large event)  

   From the Menu Bar choose Settings > Helicorder

Set the Gain to 25  

At this point, the trace (visible wiggles) is commonly 

recording offscreen and will not be visible until 

adjusted.  The goal is to line up the trace on the

bottom (blue) hour line. To do this slowly move the 

 potentiometer (black knob  Figure 12) on the AS 1 

interface box until the trace is visible on the screen.  

Moving the potentiometer one direction will move the 

position of the trace up on the screen and the opposite 

direction will move the trace  down on the screen.  Each 

Figure 12

line represents one hour, so the trace moves slowly 

across the screen.  The current UTC time is always 

the bottom hour line (in blue).  The screen will scroll up through the day, leaving the 

trace always recording on the bottom hour line.

AmaSeis Version 1.0 Level 2005.05.19

3.4