GDP-32
II
INSTRUCTION MANUAL
October 2002 Section 12, Page 2
12.1 INTRODUCTION
The transient electromagnetics or TEM program is a versatile electromagnetics program using
standard phase-lock stacking and averaging methods for signal-to-noise enhancement.
The standard frequency range (repetition rate) of the TEM program is from 0.0625 (16 second
period) to 32 Hz (0.03125 second period). The sample rate and window centers are controlled by
changing the frequency or pulse repetition rate.
Windows acquired at various repetition rates are as follows:
Note: The default value for the first window will always be equal to or greater than the value
shown above (e.g., 30.5
µ
s for 32 Hz) and less than two times that amount. See Section 12.14
and Section 12.7, Delays.
A magnitude calibrate buffer, labeled Time Domain Cal, is included in the main data cache.
All versions have a digital telluric filter, which we call a moving average or MAV filter, for
rejection of low frequency tellurics. This filter is active for 0.5 Hz and below.
This version of the program permits the use of a maximum of three analog channels for
repetition rates of 4 through 32 Hz, and up to eight analog channels for repetition rates of 2 Hz or
lower.
Go to GDP Section 6 for information concerning calibration, synchronization and generic
operation of all programs.
Go to the end of this TEM program manual for suggestions on connecting the receiver for field
measurements.
Frequency WINDOWS
(Repetition 50% Duty Cycle 100% Duty Cycle
Rate) Nr. First Last Nr. First Last
32 Hz 22 30.5 µs 6.07 ms 25 30.5 µs 12.1 ms
16 Hz 25 30.5 µs 12.1 ms 28 30.5 µs 24.2 ms
8 Hz 28 30.5 µs 24.2 ms 34 30.5 µs 48.4 ms
4 Hz 31 30.5 µs 48.4 ms 34 30.5 µs 96.7 ms
2 Hz 31 61.0 µs 96.7 ms 34 122.1 µs 193.5 ms
1 Hz 31 122.1 µs 193.5 ms 34 244.1 µs 387.0 ms
0.5 Hz 31 244.1 µs 387.0 ms 34 488.3 µs 773.9 ms
0.25 Hz 31 488.3 µs 773.9 ms 34 976.6 µs 1,548 ms
0.125 Hz 31 976.6 µs 1,548 ms 34 1.953 ms 3,096 ms
0.0625 Hz 31 1.953 ms 3
096 ms 34 3.906 ms 6
191 ms
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