Guralp Systems CMG-40T - Manual (Page 23)

Operator's guide
4 Calibrating the 40T
4.1 The calibration pack
All Güralp sensors are fully calibrated before they leave the factory. Both
absolute and relative calibration calculations are carried out. The results are
given in the calibration pack supplied with each instrument:
Works Order : The Güralp factory order number including the instrument, used
internally to file details of the sensor's manufacture.
Serial Number : The serial number of the instrument
Date : The date the instrument was tested at the factory.
Tested By : The name of the testing engineer.
There follows a table showing important calibration information for each
component of the instrument, VERTICAL, NORTH/SOUTH, and EAST/WEST.
Each row details:
Velocity Output (Differential) : The sensitivity of each component to velocity at
1 Hz, in volts per m/s. Because the 40T uses balanced differential outputs, the
signal strength as measured between the +ve and –ve lines will be twice the true
sensitivity of the instrument. To remind you of this, the sensitivities are given as
2 × (single-ended sensitivity) in each case.
Mass Position Output : The sensitivity of the mass position outputs to
acceleration, in volts per m/s². These outputs are single-ended and referenced to
signal ground.
Feedback Coil Constant : A constant describing the characteristics of the
feedback system. You will need this constant, given in amperes per m/s², if you
want to perform your own calibration calculations (see below.)
Power Consumption : The average power consumption of the sensor during
testing, given in amperes and assuming a 12 V supply.
Calibration Resistor : The value of the resistor in the calibration circuit. You
will need this value if you want to perform your own calibration calculations
(see below.)
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