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Last modified by robert on 2026/02/27 19:58
From version 101.1
edited by robert
on 2026/02/13 22:03
Change comment: There is no comment for this version
To version 102.1
edited by robert
on 2026/02/16 17:44
Change comment: There is no comment for this version

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416 416  
417 417  ----
418 418  
419 += Instrument Response =
420 +
421 +We are aware that there are various different published responses for these instruments and trust very few of them. One has to be careful with how polarity is handled between groups as well, as well as if one is working in integer counts (the ANSIR default) or mV (why anyone uses this is beyond our comprehension). The response information published below is in counts and seems to fit well in huddle tests. Note that these all appear to be sample rate insensitive, and the IGU data has been inverted (multiplied by -1) as described here: [[5Hz Node Polarity Issues>>https://auspass.edu.au/xwiki/bin/view/Data/AusPass%20Data/#HSmartSoloNodePolarityIssues]]
422 +
423 +== IGU16-3C ==
424 +
425 + '16HR3C': {'poles':[(-22.211059+22.217768j), (-22.211059-22.217768j)],
426 + 'zeros':[0j, 0j],
427 + 'gain':1,
428 + 'sensitivity': 257019225.55108312}
429 +
430 +[[Caption>>image:IGU16_Z_huddle.png]]
431 +
432 +[[Caption>>image:IGU16_N_huddle.png]]
433 +
434 +== IGU16-1C ==
435 +
436 +== BD3C-5 ==
437 +
438 + 'BD3C': {'poles':[(-1720.4+0j), (-1.2+0.9j), (-1.2-0.9j)],
439 + 'zeros':[(14164+0j), (-7162+0j), 0j, 0j],
440 + 'gain':1.69726e-05,
441 + 'sensitivity': 702651512.6046528}
442 +
443 +== Horizontal noise & how to avoid ==
444 +
445 +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.
446 +
447 +[[Power spectrum huddle test vs a CMG-6TD (S1) and TC120/Centaur combo, all filtered 0.5-5 Hz. The N and E channels have excess noise above 10Hz due to "sticking up" out of the ground.>>image:IGU16_spectrum.png]]
448 +
419 419  = **Cleaning** =
420 420  
421 421  When assembled, the nodes are water resistant but not submersible. They can handle a good spray and wipe-down. A strong, non-wire brush is helpful to reach areas between the metal spikes on the bottom.
IGU16_N_huddle.png
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IGU16_spectrum.png
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