NATURAL SOURCE MAGNETOTELLURICS
Section 13, Page 11 May 2002
Use
Home
SELECT UP
or
SELECT DN
End
to change.
OUT - All notch filters bypassed.
60 - 60 and 180 Hz notch filters enabled.
60,5 - 60, 180, 300 and 540 Hz notch filters enabled.
Other standard selections are:
50 - 50 and 150 Hz notch filters enabled.
50,5 - 50, 150, 250 and 450 Hz notch filters enabled.
50/60 - 50, 150, 60 and 180 Hz notch filters enabled.
Remember that powerline notch filters inject noise into the system, and should only be used
when absolutely necessary.
.0938- 4 Frequency band selected. Use
Home
SELECT UP
or
SELECT DN
End
to change bands.
Options are:
384 - 8192
48 - 1024
3 - 64
.0007 - 4 (.0938- 4 is the 6th level of this band)
Point Count This indicator is displayed for the low frequency band only, and provides
an indicator to the operator as how far along the program is in its data acquisition. For the
6th level of decimation shown here, the total number of points acquired for each time series
is 8285. For the 13th level, this increases to 1.061 million points.
Stacks. The total number of time series records specified to be acquired and processed at
this frequency band. Here the setting is for 5 time series of 8285 data points each.
6 Levels. The number of decimation levels selected for the low frequency band.
Levels of decimation available are as follows:
Only the low frequency band permits selection of decimation levels. All of the rest are fixed
at 5 levels. Accordingly, the level prompt only appears for the low frequency band. Refer to
the Introduction to this chapter for the frequency content of the medium, high and very high
bands.
Level Frequency band
2 1.5 - 4 Hz
3 .75 - 4
4 .375 - 4
5 .1875 - 4
6 .0938 - 4
7 .0469 - 4
8 .0234 - 4
9 .0117 - 4
10 .0059 - 4
11 .0029 - 4
12 .0015 - 4
13 .0007 - 4
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