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Since we're going to open the MC1 tank tomorrow, I've moved the MC1 accelerometers and the Guralp over to underneath MC2 for the vent. I'll reconnect them later.
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I've put both Guralps next to the Ranger and connected them to the breakout box. The data is now good.
I found that the Ranger was not centered and so it was stuck (someone kicked it in the last 2 weeks apparently). I recentered the mass according to the procedure in the manual. Its now moving freely.
In order to do a better huddle test, I increased the gain of the Ranger's SR560 preamp to 100 from 10 and put it on the low noise setting. I also enabled a 2x lowpass at 3 kHz for no good reason.
I couldn't find what the actual value of the gain of the Guralp breakout box is, but I assume its 10. With this assumption the calibrations are this:
Guralp: 800 V/(m/s) * 10 (V/V) * 16384 cts/V => 7.63e-9 (m/s)/count (0.03 - 40 Hz)
Ranger: 345 V/(m/s) * 100 (V/V) * 16384 cts/V => 1.77e-9 (m/s)/count (above 1Hz)
To account for the fact that I am not damping the Ranger with an external damping resistor, I have changed the calibration poles and zeros: in DTT we now use 2 poles @ 0 Hz and a complex pair at 1 Hz:
G = 1.77e-9
Poles = 0, 0
Zeros = 0.15 0.9887
I think that the Guralp gain is too high by a factor of 2. To really do this right, we should attach a known voltage to the input pins of the Guralp breakout and then read off the amount of counts. |