Promax PROMAX-4, Руководство пользователя

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USER’S MANUAL. PROMAX-4
Novembre 1999 Page 17
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Example 6. Measuring a signal outside the measurement range. The sound
subcarrier in channel 44 (655.25 MHz + 5.5 MHz = 660.75 MHz).
•
El nivel de ruido del equipo se encuentra entre los 5 y 7 dB
µ
V. Esto significa que el
equipo puede medir señales entre 10 y 20 dB
µ
V. El signo “<” aparece para indicar
que en esta zona de medida puede que no se cumpla la precisión especificada,
pero en la mayoría de los casos es una medida válida a todos los efectos.
4.2.3 Selection of the attenuators
AUTO attenuation
When the instrument is operated in a normal way must be switch to the AUTO
position. This means that the instrument is calculating continuously the optimum
attenuator value depending on the input signal. In order to verify that the
attenuation is set to AUTO mode just push the ATT key and check the AUTO
indication is appearing on the display. In the case it does not appear on the
display then turn the knob until AUTO is displayed. Push again on ATT key and
the instrument will be set to automatic attenuation mode.
Example 7. Checking whether the instrument is in AUTO mode.
+ AUTO +
Manual attenuation
In the measurement of certain signals in particular situations (the presence of
high level carriers which create intermodulation products and saturation effects),
it is necessary to set the attenuation value manually. To do this, press the ATT
key [10]. By turning the rotary switch [4], the user can select the attenuation in
the input from 0 to 70 dB.
The diagram below shows the order of selection using the rotary switch of the
ATT function.
Figure 7.- ATT function
Following table displays the attenuator values which are used for every signal
level. Should the selected attenuator value not be adequate for the signal level available
a "<" or ">" symbol will appear on the display thus indicating that the attenuator value
must be changed again.
Once all required measurements are performed, AUTO mode attenuation should be
restored. Push ATT key, turn the knob until AUTO is selected and push ATT key again.