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Message ID: 5018     Entry time: Fri Jul 22 14:22:13 2011
Author: Ishwita, Manuel 
Type: Update 
Category: PEM 
Subject: STS-2 seismometer hardware testing 

We have two STS-2 seismometer boxes... the blue box & the purple box. Initially we used the blue box for the STS-2 seismometer (named Bacardi by Jenne).

  • Oscilloscope powered on battery was used to test the blue box by observing the velocity output of the three axes (X, Y, Z).  It was found out that the mean value of DC volt of...

X = +10 V

Y = +11 V

Z = -0.1 V

Thus, X and Y axes showed abnormally high DC volt. It was also found out that in AC coupling mode of the oscilloscope... changes were observed in the signal received from Z axis when some seismic wave was generated near the Bacardi by jumping near it. No such changes were observed from signals received from X & Y axes.

  • We removed the blue box and used the purple box for the same Bacardi seismometer & used the oscilloscope powered on battery to test it. It was found out that the mean value of DC volt of...

X = +4.4 V

Y = +4.4 V

Z = +4.4 V

In Ac coupling mode of the oscilloscope... changes were observed in the signals from X, Y, Z axes when someone jumped near Bacardi.

  • The above voltages from the two STS-2 seismometer boxes are unsuitable for the ADC box since it works with voltages ranging from +2 V to -2 V.... meaning it will consider any voltage signal above +2 V as +2 V and any signal below -2 V as -2 V. Hence we need to find out how to use these STS-2seismometer boxes with the ADC box.
  • We also tried measuring the DC volt from the shield and the center of a BNC connector corresponding to Y axis of the purple box (lets call it 'BNC-test') by using BNC-to-banana adaptors and banana wires. Signal from shield of BNC-test was sent to oscilloscope's channel 1 (connected to center of its BNC connector) and signal from center of BNC-test was sent to oscilloscope's channel 2 (connected to center of its BNC connector). On the oscilloscope screen it was observed that both the signals gave the same mean voltage output (-2.2V).
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