FAST TRANSIENT ELECTROMAGNETICS PROGRAM
Section 19, Page 3 October 2002
19.2 NANOTEM HOOKUP DIRECTIONS
Using a 20 X 20 m Transmitter Loop and NT-20 or NT-32 Transmitter
1. Use the 1 K-ohm bridge that is supplied. Plug it into the input for the channel that has the
NanoTEM card (channel 3 in this example), and connect the ground wire to COM.
2. The 150 ohm resistor mounted on the Pomona plug must be connected across the receiver
coil as shown in Section 19.9.
3. Observe the color-coded hookups as shown to get the proper polarity for received data.
4. VERY IMPORTANT: Upon turn-on, the NT-20 transmitter may come up on a setting other
than a 20 meter loop. You MUST set it to the proper loop size to get the proper turn-off
time.
5. For 20 meter loop operation, run the TX at 3 amps. Maximum current is about 4 amps.
6. Insulate the clips on the ends of the 20 meter TX loop sections to make sure you do not have
leakage. This is not necessary in very dry conditions.
7. Do the same for the resistor load on the RX antenna, which is 5x5 meters for this example.
8. Header information from Menu 1:
Array Type : NanoTEM
Duty cycle : 50%
Receiver moment : 250
Transmitter X,Y : 20 , 20 Turns: 1
TX delay : 1.5 microseconds
Antenna delay : 2 microseconds
Transmitter type : NT-20 or NT-32
Automatic gain mode
Alias filter IN
9. Note that the receiver moment is set to 250 meters squared even though the RX loop is 5 x 5
meters. The extra factor of 10 compensates for a gain of 10 on the NanoTEM card.
10. If using the NT-32 transmitter, pressing the GAIN/F10 key, then entering 8 from the data
collection menu will accesses configuration of the NT-32 internal transmitter. The damping
resistor should be set to 250 and transmitter loop size set to 20.
11. Take two stacks of 1024 cycles, unless the data are coming in clean with shorter stacks.
Using Transmitter Loops Other Than 20 Meters
If you are using an NT-20 transmitter, be sure to set the LOOP SIDE switch on the NT-20 to the
closest smaller value for the transmitter loop being used. For example, a 61-meter loop should
be set to 50 meters on the NT-20. The new loop dimensions should also be entered in Menu 1.
If you are using an NT-32 transmitter, the damping resistor value may be changed to correspond
to the loop dimensions. A chart for estimated damping resistor values is included at the end of
Section 19.3.
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