GDP-32
II
INSTRUCTION MANUAL
October 2002 Section 12, Page 6
Duty cycle. Two different TEM options are accessed in Menu 1:
50% (default): bipolar 1/4 period on, 1/4 period off, standard time domain waveform.
100% Frequency domain waveform for LOTEM and experimentation.
Windows. Three choices are available:
Zonge Standard: logarithmic window spacings as shown in Sections 12.8 and 12.9
for TEM and Sections 12.23.1 and 12.23.2 for NanoTEM
Shallow: higher density early time window spacing for NanoTEM only. See
Section 12.23.3.
Equal Interval: data are acquired on an evenly spaced time sample and stored on
disk. The first 31 samples are also stored in the data cache. See Section 12.16.
Receiver Moment. Receiver antenna moment in square meters. The default value is
10,000 m
2
, which is the moment of the TEM/3 antenna.
Note: The NanoTEM boards have an extra gain of 10 installed, so the equivalent area
for the receiver moment is 10 times the physical size. For example, a 5 x 5 meter receiver
loop would have a moment of 25 x 10, and the value input for the Receiver Moment
would be 250.
Transmitter X, Y. Dimensions of the transmitter loop (or dipole) in meters.
Turns. Number of turns in the transmitter loop. Default is 1.
Tx Delay. Turnoff time of the transmitter, in microseconds.
Antenna Delay. Inherent delay of the receiver coil and filters, in microseconds.
The RVR and TEM/3 coils have delays of approximately 15 microseconds.
Transmitter Type. The options here are GGT Series, NT-20, or NT-32 (for the
embedded Tx version). Specifying the NT-20 transmitter permits the receiver to control the
transmitter - turning it on for data acquisition and off after acquisition - thus extending the
battery life.
Robust Filter. This filter was added at the request of several clients, and has 3
options:
None: standard linear (mean) stacking and averaging.
Median: median averaging
Trimmed mean: mean calculation after rejecting a percentage of the outliers. The
rejection limits are selectable between +/- 12.5%, 25% and 37.5%.
Note: Field tests have determined that the best averaging method in the presence
of powerline noise is standard linear mean averaging.
Gain Mode. The default mode is Standard, which adjusts the gains for a maximum
voltage of 2.5 Volts. The other option is Noisy, which limits the gains to obtain a
maximum voltage of 1.0 Volts. See GDP Section 6.5, Gains.
Units. The operator can select meters or feet. The default is meters.
Alias. The operator can lock the antialias filter out - for experimental use only.
The antialias filter should always be IN for normal operation.
To Next Page
