Guralp Systems CMG-DM24 - Manual (Page 72)

CMG-DM24
Instructs the DM24 to inject a square-wave (step function) calibration
signal, consisting of a positive step on the start of the next clock
minute, followed by a negative step some minutes later (by default, 2).
The calibration is disconnected the same number of minutes after the
negative edge.
component specifies which component is to be calibrated: one of Z,
N/S, E/W, or ALL. Some sensors use only the Z calibration loop for all
three components.
You can alter the duration of each step using the MINUTE command,
described below.
Whilst calibration is in progress, the fourth (auxiliary, or X) data
channel is switched to monitor the returning calibration signal.
RANDOMCAL
Syntax: component RANDOMCAL
Instructs the DM24 to inject a white-noise calibration signal generated
by an onboard pseudo-random number generator.
component specifies which component is to be calibrated: one of Z,
N/S, E/W, or ALL. Some sensors use only the Z calibration loop for all
three components.
The calibration signal will be automatically disconnected after 2
minutes if you have not altered the setting using the MINUTE
command, described below.
Whilst calibration is in progress, the fourth (auxiliary, or X) data
channel is switched to monitor the returning calibration signal.
The pseudo-random number generator produces true white noise over
the entire passband, as shown in the power spectral density plot
below:
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