2 calibration methods – Guralp Systems CMG-3ESPCD User Manual
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CMG-3ESPCD Digital Broadband Seismometer
Calibrating the 3ESPCD
If you want to repeat the calibration to obtain more precise values at a
frequency of interest, or to check that a sensor is still functioning correctly,
you can inject calibration signals into the system using a Güralp digitiser or
your own signal generator, and record the instrument's response.
4.1.3 Obtaining copies of the calibration pack
Our servers keep copies of all calibration data that we send out. In the event
that the calibration information becomes separated from the instrument, you
can obtain all the information using our free e-mail service. Simply e-mail
with the serial number of the instrument in the subject
line, e.g.
The server will reply with the calibration documentation in Word format.
The body of your e-mail will be ignored.
4.2
Calibration methods
Velocity sensors such as the 3ESPCD are not sensitive to constant DC levels,
as a result both of their design and because of the interposed high-pass filter.
Instead, three common calibration techniques are used.
•
Injecting a step current allows the system response to be determined in
the time domain. The amplitude and phase response can then be
calculated using a Fourier transform. Because the input signal has
predominantly low-frequency components, this method generally gives
poor results. However, it is simple enough to be performed daily.
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Issue B - November 2013