Rohde & Schwarz UPD, Application Note

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1GA16_1L.DOC ROHDE & SCHWARZ 22
Note :
1. After 10 measurements the control routine is terminated even if the STOP softkey is not pressed.
This also applies when the desired output power cannot be reached with the generator voltage
defined as MAX VOLT.
2. Upon termination of the control routine, the current generator voltage becomes the new default
voltage which is stored together with the other settings of the POWERAMP softkey menu when
the application is quit.
Selecting the POWERAMP menu implies that the power measured in the subsequent main measurement
(response or sensitivity) is displayed on trace B as a curve or bargraph. If this is not desired (eg because
the 2nd scale at the right-hand side of the curve or the 2nd curve are disturbing), trace B is to be switched
OFF again
•
prior to the first main measurement by briefly returning to level 2 and reselecting the measurement
mode (not recommended in the FFT noise mode because of the noise generation time) or
•
after the first main measurement by changing to the UPD display panel (see section 7.1, Change of
Task Application/User Interface) and manual switch-off (OFF) of trace B.
5.2.3 Entry of Microphone and Room Parameters
The MICROPHN or MIC&ROOM softkey (F10, level 3) opens a softkey menu (level 4) for entering
microphone and (in the case of sweep measurements) room parameters such as:
•
sensitivity of standard microphone in mV/Pa (SENSITIV, F6);
•
gain factor of microphone amplifier in dB (GAIN, F7), with no microphone amplifier connected a GAIN
of 0 dB must be set;
•
distance between standard microphone and loudspeaker in m (DISTANCE, F8) so that the sound
travel time can be taken into account.
For sweep measurements (FREQ SWP or BRST SWP) the room parameters are entered in addition:
•
Shortest echo path in meters (ECHOPATH, F9). Loudspeaker and standard microphone should be set
up (in not completely sound-absorbing rooms) so that the echo path is as long as possible (see 5.2.1,
Test Setup).
•
Reverberation time in milliseconds (REVERBER, F10). A new burst measurement is delayed by this
time to exclude echoes from the previous measurements.
The reverberation time can be determined using the WAVEFORM function. The generator is set to sine
burst with a few periods of switch-on time and a long measurement interval (eg 60 s). A (single) waveform
measurement reveals the burst periods and the decay of the reverberation. With the aid of the graphics
cursor and the *-o function, the time between the end of the burst and the disappearance of the
reverberation can be directly read.
When the sound pressure unit is selected (see section 5.2.4) the reference values for RMS measurement
and display scaling are obtained from the entered microphone parameters.
Note : Microphone parameters are stored when the application is quit (SPEAKER.CFG) and reloaded
on the next call up. The default values for common 1/2" microphones such as B&K or Microtech
Gefell are 50 mV/Pa, 0 dB (without additional microphone gain) and 1-m measurement distance.