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Spectrum Analyzer
Eaglepride82:
I have an old Spectrum Analyzer (HP8591EM - EMC ANALYZER) and I would like to Measure the Amplitude and Frequency (Sound Level) of audiable noise that is present from coil whine of a common mode inductor. Basically, is there an easy way to connect a microphone to a spectrum analyzer? Is there a simple preamp circuit than can be used with the microphone? The purpose for these measurements are to demonstrate different dampening techniques and record sound level reductions.
bob91343:
That spectrum analyzer probably isn't suitable. It doesn't have the required frequency resolution to analyze audio signals.
I have a similar model 8594L and its best resolution is 300 Hz and not too good there at that.
Eaglepride82:
OK. THanks. This analyzer will scan 9kHz to 1.8GHz. I was hoping I could put it in continuous sweep mode and scan the range from 15kHz to 20kHz.
TimFox:
For audio purposes, the 9 kHz lower bound on typical SAs is a nuisance. Within the range of your unit, you could use a preamplifier after a reasonable microphone. In my collection, I have an -hp- 465A and two PARs: 113 and 117/114.
The 465A has a fixed bandwidth (covering audio up to about 1 MHz), a high-Z single-ended input, and can drive 50 ohms.
The two PARs have high-Z differential inputs and selectable hp and lp filters. The 113 has a 600 ohm output (needs a pad to drive 50 ohms neatly), while the 117/114 combination can drive 50 ohms. I don’t offhand know the modern equivalents.
daqq:
Unless there's something weird going on you should be able to pull it off with an oscilloscope + simple preamplifier.
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