BRUEL & KJAER 2663, Technical Documentation Manual

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Chapter 3 — Operating Characteristics
Output Noise and Dynamic Range
Preamplifiers Types 2663 and 2663 B
User Manual
BE 1068 – 12
29
3.5 Output Noise and Dynamic Range
Broadband 3 Hz to 20 kHz output noise produced by the preamplifiers when powered
from a +25 V dual-polarity supply is shown in
Fig.3.9 . This was measured with pream-
plifier minimum sensitivity set to 1 mV/pC and a 2 nF capacitor terminating the input,
simulating the source capacitance of a transducer with connection cable.
Fig.3.9 Third-octave noise spectrum produced by Types 2663 when powered from a ±28 V dual-
polarity supply. The measurement was made using a Brüel & Kjaer Dual Channel Real-time
Frequency Analyzer Type 2133
With higher values of input source capacitance, the output noise level increases, as
shown in
Fig.3.10 . The preamplifiers, as well as their input and output connection
cables, should be well anchored to minimise noise.