GDP-32
II
INSTRUCTION MANUAL
October 2002 Section 12, Page 10
Cycle. Specify the number of cycles to average. Increments are in binary steps from 1 to
16,384. Use
Home
SELECT UP
or
SELECT DN
End
to change. As the system acquires data, the cycle count will
be updated in real-time to the left of the number input by the operator.
Tx Curr. Transmitter current in amperes.
Window. The default is window number 16, which in this case occurs at 1.549 ms, for the
given transmitter turnoff time, antenna delay, and alias filter delay. This window is
monitored for run-time statistics and is user-selectable. Window center times are defined as
the time interval occurring after the turnoff of the transmitter current (Tx current is zero).
Delay. Delay in sampling to allow for turnoff time of the transmitter and delays in the
antenna and anti-alias filter.
Delay increments are in multiples of the sample period. In this example, using a 32 Hz
repetition rate, the sample period is 30.5 µs. The default program adjusts the delay time so
that the first window is at least one sample period after transmitter turnoff (loop current
equals zero amps). Hence in the Menu 4 example above, using default values of 50 µseconds
delay for the transmitter to turnoff, 15 µsec for the antenna delay and 26 µsec for the anti-
alias filter delay, we have a total delay of 91 µsec. Now add 30.5 µsec to that for one sample
period for a total of 121.5 µsec. This means that we want the first sample (first window) to
occur at least 121.5 µsec after the beginning of the turnoff ramp.
If we delay 4 sample periods (4 times 30.5 µs) the first window will occur 122.6 µsec after
the beginning of transmitter turnoff ramp, and 31.6 µsec (122.6 - 91) after the end of the
ramp. Thus, the first window will occur at 31.6 µsec in the data printout.
The delay time can be user adjusted for various tests and for measuring the complete
transient during transmitter turnoff.
See Section 12.14 for a graphic display of the combination of turnoff time and delays.
Alias. The antialias filter delay is fixed by the corner frequency and is displayed for the
operator’s convenience. See Section 12.7.
Station. Station number. Can be accessed in either Menu 3 or 4 for ease in changing
values during a survey. Our data processing programs sort first on Station, second on Rx
and third on Tx.
TxON. If the Transmitter Type is set to NT-20 in Menu 1, and the transmitter is
being controlled by the receiver, the transmitter will be automatically turned on and off by
the program when acquiring data. The key gives the operator manual control for
checking gains, etc. If the label above is TxON, pressing will turn the
transmitter ON; if it is labeled TxOFF pressing will turn the transmitter OFF. Any
operator keystroke will be overridden by the program during data acquisition.
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