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keiko.kokeyama - 16:09 Thursday 14 April 2016 (1537) Print this report
Wrong input filters for BS EX EY seismometers
I have noticed that wrong input filters were applied to BS, EX, EY seismometers. I have turned the filters off, and now the output dimension is velocity. But the absolute value of the output is arbitrary. Sensors' frequency dependencies are not compensated. I will try to fix it in my next shift if no one does it by then.

A seismometer placed around MCF is called RION seismometer. Its output is acceleration. Digital input filters are applied (by Shimoda-kun??) to convert it to displacement, and also to compensate the frequency response of the sensor. On the other hand, EX, EY, BS seismometers' outputs are in velocity. I noticed that the filters from MCF seismometer were applied to BS EX and EY, which is not right.
Comments to this report:
Shimoda, Araya, Hayama - 0:19 Saturday 16 April 2016 (1547) Print this report

Today I changed the digital filters of seismometers at 2016/4/15 22:30 JST. The output unit has been changed.


for BS,EX,EY (Trillium Compact)

 - output signals are in unit of velocity [m/s]   ( output channels: K1:PEM-BS(/EX/EY)_SEIS_NS(/WE/Z)_SENSINF_OUTPUT )

 - frequency band : 0.012-80Hz (+-1dB region)

for MCF (RION)

 - output signal is in unit of acceleration [m/s^2] ( output channel: K1:PEM-MCF_SEIS_Y_SENSINF_OUTPUT )

 - frequency band : 0.1-100Hz (+-1dB region)


The frequency dependence of seismometer's response is not corrected. So the filter is valid only for each frequency band (written above). If the correction is necessary, please see the manual. Attatched file is Trillium manual.

The source impedance of Trillium is 150[ohm], and the input impedance of digital system is 10k[ohm]?  so the signal can become ~97% of original output. It should be calibrated if necessary.



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