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TM-11-6625-2872-14&P
SECTION I
GENERAL INFORMATION
1-1. DESCRIPTION.
1-2 The 8808A is a Log Level Preamplifier which
produces a dc output proportional to the logarithm of
the ac input signal, over an extremely wide range of
signal amplitudes. The input signal dynamic range
can be up to 100 dB (100,000:1). In addition, a
50 dB (320:1) span is provided for greater signal resolution
1-3. The Preamplifier is designed for use with low
output impedance accelerometers, as well as vibration
and acoustic transducers, which have outputs in the
frequency range of 5 Hz to 100 kHz. It is also useful
for continuous monitoring or recording of signal output
in dB during frequency analysis of amplifiers, filters,
transmission networks, and similar devices.
1-4. The 8808A can be plugged into Sanborn direct
writing recording systems. When used with recorders
having 50 division chart paper, the calibrated output is
2 dB per division for the 100 dB span, or 1 dB per
division for the 50 dB span. Also, the preamplifier
can be benchtop or rack mounted, with the output
connected to a monitoring instrument such as a
voltmeter or oscilloscope. For recording, a strip
chart recorder or magnetic tape recorder can be
connected to the output.
1-5. The range switch provides nine bottom scale
sensitivities in 10 dB steps from 0 dBV to -80 dBV
(dBV = decibels referred to 1 volt RMS). For the
50 dB span, the full scale signal is 50 dB above the
bottom scale level. For the 100 dB span, the full scale
signal is 100 dB above the bottom scale level.
1-6. All nine RANGE switch positions can be used with
the 50 dB span. The four switch positions outlined in
red on the panel (-50, -60, -70, -80) are used for the 100
dB span only.
1-7. Specifications for the 8808A Log Level Preamplifier are
given in Table 1-1.
Figure 1-1. 8808A Log Level Preamplifier
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