Inside the 3TB
6.3.2 Conventional-response feedback
The
conventional-response
feedback system has an additional parallel feedback
circuit, consisting of a non-inverting integrator in series with a resistor. This
arrangement results in two poles at specified frequencies. The velocity response of a
conventional-response system is defined by a transfer function identical to that of a
conventional long-period sensor with a damping constant ζ of 0.707 (1/√2)
The seismometer can be supplied with an equivalent resonant frequency of 0.033 Hz
(30 s), 0.01 Hz (100 s) or 0.0083 Hz (120 s) as required. An active low-pass filter
provides a high-frequency cut-off point at a frequency you specify.
6.3.3 Comparisons
The figures below plot the comparative response of a conventional velocity output
broadband sensor and a hybrid output broadband sensor. The upper graph shows
the response in terms of output against input acceleration in units of V/ms
-2
, whilst
the lower graph is plotted in terms of output against input velocity, in V/ms
-1
.
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Issue G - November 2019
