Elekta Neuromag NM21283A, Руководство пользователя

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NM21283A-A 11
3
C H A P T E R 3
Basic tuning operations
This chapter explains how to measure white noise level of the sensors,
automatic fine tuning, and heating of the sensors.
3.1 Measuring the sensor noise level
The tuner program can be used to check the white noise level of all the
sensors. This can be done before the measurements to check that all chan-
nels are working properly.
To measure white noise levels using Tuner:
1. Stop any ongoing acquisition by pressing stop button of the acquisition
program, and wait for the measurement to stop.
2. Start the tuning program (if not running yet). See “Beginning a ses-
sion” on page 9.
3. Press the large “Measure noise” button on the left.
Warning: If there was a measurement running when the tuner was
started, the start button is gray, and no tuner measurements can be initi-
ated. In this case, one must exit the tuner, stop the normal acquisition
measurement, and then restart the tuner again.
Warning: Acquisition program can not perform measurements if the
tuner is accessing the measurement system. To enable measurements,
press stop button to stop current operation, and then another time to
release the collector (software part responsible for delivering the magne-
tometer data). It is recommended that you then exit the tuning program,
even though that is not necessary to perform normal acquisition.
The program now starts measuring the noise level of the system. The
noise level of all channels is shown on a bar display in the display area.
Normally all bars should be red and display value between 2 to 5
(
for gradiometers). Small negative bars indicate channels
that are saturated and probably are not operating in flux locked mode (not
functioning properly). Note that the colors can be adjusted personally. The
above description refers to default colors.
fT Hz
⁄
fT cm Hz
( ) ⁄