Guralp Systems CMG-5T - Manual (Page 19)

Operator's Guide
The sensor transfer function
Most users of seismometers find it convenient to consider the sensor
as a “black box”, which produces an output signal V from a measured
input x. So long as the relationship between V and x is known, the
details of the internal mechanics and electronics can be disregarded.
This relationship, given in terms of the Laplace variable s, takes the
form
( V / x ) (s) = G × A × H (s)
In this equation
•
G is the acceleration output sensitivity (gain constant) of the
instrument. This relates the actual output to the desired input
over the flat portion of the frequency response.
•
A is a constant which is evaluated so that A × H (s) is
dimensionless and has a value of 1 over the flat portion of the
frequency response. In practice, it is possible to design a system
transfer function with a very wide-range flat frequency
response.
The normalising constant A is calculated at a normalising
frequency value fm = 1 Hz, with s = j fm, where j = √–1.
•
H (s) is the transfer function of the sensor, which can be
expressed in factored form:
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