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
