Calibrating the 3TB
Before you can calibrate the instrument, its calibration relays need to be activated by
pulling low the
CAL ENABLE
line on the instrument's connector for the component
you wish to calibrate. Once enabled, a calibration signal provided across the
CAL
SIGNAL
and
SIGNAL GROUND
lines will be routed through the feedback system. You
can then measure the signal's equivalent velocity on the sensor's output lines.
Güralp Handheld Control Units provide a switch for activating the
CAL ENABLE
line.
This is most easily done using Scream, as described in the next chapter.
Note:
Unlike surface 3T instruments, the 3TB has only one
calibration enable line for all components.
5.3 Calibration with Scream!
Güralp digitizers provide calibration signal generators to help you set up your
sensors. Calibration is most easily done through a PC running Güralp's Scream!
software.
Depending on the digitizer type, sine-wave, step and broadband noise signal
generators may be available. In this section, broadband noise calibration will be
used to determine the complete sensor response in one action. Please refer to the
digitizer's manual for information on other calibration methods.
1. In Scream!'s main window, right-click on the digitizer's icon and select
Control...
. Open the
Calibration
pane.
2. Select the calibration channel corresponding to the instrument, and choose
Broadband Noise.
Select the component you wish to calibrate, together with a
suitable duration and amplitude, and click
Inject now
. A new data stream,
ending
C
n
(
n
= 0 – 7) or
MB
, should appear in Scream!'s main window
containing the returned calibration signal.
54
Issue G - November 2019
