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Simcenter Qsources Low Frequency Monopole Source 2v9C.docx
Electronic protection
The Monopole source must be powered by an instrumentation amplifier like the Simcenter Qsources Measurement
Power Amplifier (product code: Q-AMP230V or Q-AMP115V). A high-quality audio or PA amplifier can also be used.
An undistorted RMS power output of at least 50 Watt to 8 Ohms impedance is required.
An electronic protection device is integrated in the main power cable. The including electronic protection device is
intended for this particular source only and will protect it against overload. A normal procedure to achieve maximum
level of output is to increase the amplifier output slowly until the electronic protection device acts. As soon as the
signal level becomes hazardous to the source, the internal protection circuit will start to limit the signal. When the
electronics starts to interfere, the red LED light will be activated.
1.
In the first stage, the protection circuit will first limit the voltage peaks. Depending on the signal nature,
this can sometimes be heard as an increased distortion of the sound. In this mode the source can still be
used over long periods for measurements.
2.
In the second stage, when the signal level is increased further, the protection circuit will suddenly increase
the impedance of the system that will cause a decrease in the output noise level by 10 dB or more. This
can be heard as a drop in noise level.
Warning
: When the second stage is active, the signal level should be decreased manually.
The second stage can act rapidly when excessive level is applied or it can act after a few minutes when the system
risks overheating. Also, if the second stage is active, the source should not be used for measurements, because a
large amount of electrical energy is now dissipated and both the source and the used amplifier will heat-up
considerably without significant sound or noise.
After the signal level from the amplifier is decreased manually to zero, the protection circuit will reset and once
again allow normal use.
If high noise levels are needed for measurements, it is advised to experiment with signal types and frequency
range of the applied signal. Even if this causes repeated interruption of the source by the protection circuit, such
experiments will not damage the source. This is true as long as the used power amplifier does not malfunction
(relevant when using a non- Simcenter Qsources amplifier). The Simcenter Qsources Measurement Power
Amplifier is internally protected against overload, shortcut, signal loops, etc. This procedure will normally allow
ample noise levels for normal applications.
50 Hz or 60 Hz content in the signal can also cause this problem.
When driving the source in cold conditions, a rattle noise can be heard which will decrease in time. This high
frequency rattle does not influence the FRF measurement<1000Hz.
11
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