2.9 Radio-Frequency Environment
01-999021-00 A0100
Installation Planning Guide
19
reinforcing bars, and a storage area containing steel dewars for cryogenic storage. Each site
must be carefully analyzed to ensure optimum performance of the system.
Color monitors need to be degaussed in magnetic fields above 1 to 2 gauss. If the field is
greater than 5 gauss, color monitors may need additional shielding to prevent display
distortion. Sun computers and peripherals are also affected by the magnetic field.
WARNING:
Cardiac pacemaker or metallic implant wearers must remain outside
the 5-gauss perimeter (see Chapter 4) around the magnet until safety
is clearly established. An NMR spectrometer system generates strong
magnetic and electromagnetic fields that can inhibit operation of some
cardiac pacemakers, resulting in death or serious injury to the user.
Consult the user manual provided by the pacemaker manufacturer or
contact the pacemaker manufacturer to determine the effect on a
specific pacemaker. Varian provides signs with each system to warn
pacemaker wearers of this hazard. Post the signs according to
“Posting Requirements for Magnetic Field Warning Signs” page 39
2.9 Radio-Frequency Environment
The site should be checked for radio-frequency interference (rfi) at or near the operating
frequencies of the spectrometer and most common nuclei (listed in
). The level of
any interference should be attenuated to an electrical field strength of less than 150
µ
V/m
at the site of the magnet. Interference is not uncommon when two spectrometers are located
in the same room, referenced to the same power system, or operating at the same frequency.
Spectrometer frequency ranges
Proton Frequency
(MHz)
Frequency Ranges
(MHz)
200
20 to 200.050
300
30 to 300.075
400
40 to 400.125
Table 7. Spectrometer and Nuclei Operating Frequencies
Operating frequencies for most common MERCURY-VX nuclei
Nucleus
200 Magnet
(MHz)
300 Magnet
(MHz)
400 Magnet
(MHz)
1H
199.975
300.075
400.125
19F
188.743
282.301
376.427
31P
80.950
121.470
161.972
2
H
30.699
46.063
61.425
13C
50.289
75.462
100.622
15N
20.266
30.408
40.545