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The HP 33581A has other
important features that are necessary when making measurements of small voltages from
transducers and harmonic signals. Its 30 nV sensitivity becomes important for these
measurements. Battery operation can be used to reduce the line related interference
common in low level measurements so only the real spectrum is measured.
Digital readout of tuned
frequency is located above the analog meter. It has been grouped with the meter for
ease of reading. Resolution of the digital readout is 1 Hz for any frequency between
15 Hz and 50 kHz. Readout is updated five times per second so delay between tuning
and reading is minimized.
Four meter scales are used
to provide a wide range of displays. Two scales are used for linear voltage
readings. Two log scales provide either a 90 dB or 10 dB display. In any case,
the large meter with its mirror backing can present readings in dBV, dBm or volts. A
meter was specifically chosen for amplitude display rather than digital readout because it
is easier to peak a meter reading and because it is much easier to get a feel for noise or
other amplitude variations by watching the meter. The same voltage used to drive the
meter is also available on the rear panel for driving X-Y recorders. |
