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Last modified by robert on 2026/02/27 19:58
From version 105.2
edited by robert
on 2026/02/17 12:43
Change comment: There is no comment for this version
To version 108.1
edited by robert
on 2026/02/18 14:46
Change comment: There is no comment for this version

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431 431  
432 432  [[X axis is samples (.01 s), Y axis is velocity (m/s), 0.5-5 Hz filter>>image:IGU16_Z_huddle.png]]
433 433  
434 -[[X axis is samples (.01 s), Y axis is velocity (m/s), 0.5-5 Hz filter>>image:IGU16_N_huddle.png]]
434 +[[X axis is samples (.01 s), Y axis is velocity (m/s), 0.5-5 Hz bandpass filter>>image:IGU16_N_huddle.png]]
435 435  
436 436  == IGU 16-1C ==
437 437  
438 -The 1C nodes seem to have a slightly different response to the 3C (TBA)
438 +The 1C nodes seem to have the same response as the 3-channel IGU-16HR-3C (above), however the response posted at IRIS-NRL seems to imply that there is no poles and zeros information (e.g. a flat/linear response). This is 100% not so.
439 439  
440 +[[IGU-16 1C, X axis is samples (.01 s), Y axis is velocity (m/s), 0.5-5 Hz bandpass filter. Seems to be same response as IGU-16HR-3C.>>image:IGU16_1C_Z_huddle.png]]
441 +
440 440  == BD3C-5 ==
441 441  
442 442   'BD3C': {'poles':[(-1720.4+0j), (-1.2+0.9j), (-1.2-0.9j)],
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444 444   'gain':1.69726e-05,
445 445   'sensitivity': 702651512.6046528}
446 446  
447 -*image TBA but they have been created in the past~-~- we are 100% confident our published responses are correct
449 +Above 0.5 Hz, the BD3C-5 response fits well:
448 448  
449 -== Horizontal noise & how to avoid ==
451 +[[X axis is samples (.01 s), Y axis is velocity (m/s), 0.5-5 Hz filter>>image:BD3C_Z_huddle.0.5.png]]
450 450  
451 -The 5 Hz nodes are susceptible to horizontal noise due to the placement of geophones in the units, **but this can be mitigated by completely burying the units flush with the ground.** In the below example, the node was set on the floor of our basement set on its plastic carrying case support. As such the amount of horizontal noise noticeably increases above ~~ 10Hz.
453 +[[X axis is samples (.01 s), Y axis is velocity (m/s), 0.5-5 Hz bandpass filter>>image:BD3C_N_huddle.0.5.png]]
452 452  
453 -[[Power spectrum huddle test vs a CMG-6TD (S1) and TC120/Centaur combo. The N and E channels have excess noise above 10Hz due to "sticking up" out of the ground.>>image:IGU16_spectrum.png]]
455 +(% class="wikigeneratedid" %)
456 +Below the corner frequency 0.2 Hz (5 seconds) the response still does a good job, but may need to be dialed in a bit. In the next two figures the filter is 0.1 to 5 Hz. We are looking into this..
454 454  
458 +
459 +[[BD3C **0.1 **to 5 Hz bandpass filter>>image:BD3C_Z_huddle.0.1.png]]
460 +
461 +[[BD3C **0.1** to 5 Hz bandpass filter>>image:BD3C_N_huddle.0.1.png]]
462 +
463 +== IGU-16 Horizontal noise & how to avoid ==
464 +
465 +The** 5 Hz nodes** are susceptible to horizontal noise due to the placement of geophones in the units, **but this can be mitigated by completely burying the units flush with the ground.** In the below example, the node was set on the floor of our basement set on its plastic carrying case support. As such the amount of horizontal noise noticeably increases above ~~ 10Hz.
466 +
467 +[[IGU-16HR-3C Power spectrum huddle test vs a CMG-6TD (S1) and TC120/Centaur combo. The N and E channels have excess noise above 10Hz due to "sticking up" out of the ground.>>image:IGU16_spectrum.png]]
468 +
469 +(% class="wikigeneratedid" %)
470 +The BD3C-5 nodes do not have this issue:
471 +
472 +[[BD3C-5 test, as above. There is no additional noise on the horizontal channels.>>image:BD3C_psd.png]]
473 +
455 455  = **Cleaning** =
456 456  
457 457  When assembled, the nodes are water resistant but not submersible. They can handle a good spray and wipe-down. A stiff plastic brush is helpful to reach areas between the metal spikes on the bottom.
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