Guralp Systems CMG-DM24S12AMS User Manual

Page 67

CMG-DM24S12AMS Operator's guide

All sensors are tuned at the factory to produce 1 V of output for 1 V

input on the calibration channel. For example, a sensor with an
acceleration response of 0.25 V/m/s

should produce 1 V output given a

1 V calibration signal, corresponding to 1/0.25 = 4 m/s

= 0.408g of

equivalent acceleration.

The following section explains how to calibrate 5U sensors using a

DM24 series digitiser and a computer running Güralp Systems Scream!

software.

Using a DM24 series digitiser for calibration

The CH 1 – 12 ports on the are connected to two separate internal 6-

channel digitisers. To calibrate uniaxial sensors attached to these:

1. In Scream!'s main window, right-click on the digitiser's icon and

select Control.... Open the Calibration pane.

2. The Z calibration channel is connected to ports CH1 and CH2.

Select this channel, make any other choices you require (see

“Calibration” in Section 3.2

for more details), and click Inject

now. A Mux stream ending MB should appear in Scream!'s main
window containing the returned calibration signal.

3. Open a WaveView window on the calibration signal and the

returned streams by selecting them and double-clicking. The

streams should display the calibration signal combined with the

sensors' own measurements. If you cannot see the calibration

signal, zoom into the WaveView using the scaling icons at the top

left of the window or the cursor keys.

4. If you need to scale one, but not another, of the traces, right-click

on the trace and select Scale.... You can then type in a suitable
scale factor for that trace.

5. Click on Ampl Cursors in the top right hand corner of the

window. A white square will appear inside the WaveView at the

top left. This is in fact two superimposed cursors.

6. Drag one cursor down to be level with the lowest point of the

signal trace.

March 2004