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Changes for page ANU Seismic Data Loggers

Last modified by robert on 2025/08/08 16:09
From version 60.1
edited by robert
on 2025/08/06 18:54
Change comment: There is no comment for this version
To version 64.1
edited by robert
on 2025/08/08 16:09
Change comment: There is no comment for this version

Summary

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... ... @@ -168,14 +168,43 @@
168 168  
169 169  = Instrument Response =
170 170  
171 -Both the TerraSAWR and LPR-200 use the same ADS1281 analog-to-digital converter chip and are designed to have identical instrument response. The ADC (analog to digital) chip in both loggers originally samples at 1024000 Hz and downsamples towards the output data rate via a 5th order SINC filter, then another four FIR filters. If the output is below 250 Hz, a final "pure" /5 decimation is done without any sort of FIR filter. For the most part, the data logger response essentially flat when the samplerate output is set to 100 Hz or less and for seismological purposes is likely to be impossible to detect below 20 Hz regardless.
171 +Both the TerraSAWR and LPR-200 use the same ADS1281 analog-to-digital converter chip and are designed to have identical instrument response. The ADC (analog to digital) chip in both loggers originally samples at 1024000 Hz and downsamples towards the output data rate via a 5th order SINC filter, then another four FIR filters. If the output is below 250 Hz, a final "pure" /5 decimation is done without any sort of FIR filter (for better or worse!).
172 172  
173 -{{info}}
174 -The 600+ Stage 3 SINC coefficients during the initial 1024k > 16k decimation were left off as they slowed down the process x10 and contribute at most 0.3 db amplitude and 0.31 ms phase delay discrepancies, and primarily only to frequencies near the nyquist. If for some reason you want to add this phase manually we can share the parameters with you.
175 -{{/info}}
173 +In the logger's menu, the user can choose to apply a 2nd stage "sensor gain" by selecting an instrument type in the setup menu. This effectively selects a 10 Vpp (e.g. short period sensors), 20 Vpp, 40 Vpp (most broadband sensors) regime to match the sensor's sensitivity. This has the effect of doubling amplitude from 10v to 20v, or quadrupling from 10v to 40v. If you have set your sensor correctly (and the signal isn't clipped!) you can "correct" this by simply multiplying your data by 0.5 etc. This gain manifests itself in stage 2 in the response information.
176 176  
177 -The user can choose to apply a 2nd stage "sensor gain" by selecting an instrument type in the setup menu. This effectively selects a 10 Vpp (e.g. short period sensors), 20 Vpp, 40 Vpp (most broadband sensors) regime to match the sensor's sensitivity. This has the effect of doubling amplitude from 10v to 20v, or quadrupling from 10v to 40v. If you have set your sensor correctly (and the signal isn't clipped!) you can "correct" this by simply multiplying your data by 0.5 etc. This gain manifests itself in stage 2 in the response information.
175 +//(The 600+ Stage 3 SINC coefficients during the initial 1024k > 16k decimation were left off as they slowed down the process x10 and contribute at most 0.3 db amplitude and 0.31 ms phase delay discrepancies, and primarily only to frequencies near the nyquist. If for some reason you want to add this phase manually we can share the parameters with you.)//
178 178  
177 +You might notice that the response information may come in two versions. The response from our website (see link below) includes the 2nd "sensor gain" stage for clarity. e.g. here is a Trillium Compact 120 & ANU Logger response
178 +
179 +##Channel Response
180 + From M/S (Velocity) to COUNTS ()
181 + Overall Sensitivity: 3.95452e+08 defined at 1.000 Hz
182 + 8 stages:
183 + Stage 1: PolesZerosResponseStage from M/S to V, gain: 754.3
184 + Stage 2: ResponseStage from V to V, gain: 0.25
185 + Stage 3: CoefficientsTypeResponseStage from V to COUNTS, gain: 2.09715e+06
186 + Stage 4: FIRResponseStage from COUNTS to COUNTS, gain: 1
187 + Stage 5: FIRResponseStage from COUNTS to COUNTS, gain: 1
188 + Stage 6: FIRResponseStage from COUNTS to COUNTS, gain: 0.99998
189 + Stage 7: FIRResponseStage from COUNTS to COUNTS, gain: 1##
190 +
191 +
192 +However, if retrieving from AusPass or IRIS, the 2nd "sensor gain" stage is combined with the logger gain. This has no affect, but you may detect that the former Stage 2 V->V ResponseStage has been merged into the Stage 3 gain.
193 +
194 +##Channel Response
195 + From M/S (Velocity) to COUNTS ()
196 + Overall Sensitivity: 3.9546e+08 defined at 1.000 Hz
197 + 6 stages:
198 + Stage 1: PolesZerosResponseStage from M/S to V, gain: 754.3
199 + Stage 2: CoefficientsTypeResponseStage from V to COUNTS, gain: 524288
200 + Stage 3: FIRResponseStage from COUNTS to COUNTS, gain: 1
201 + Stage 4: FIRResponseStage from COUNTS to COUNTS, gain: 1
202 + Stage 5: FIRResponseStage from COUNTS to COUNTS, gain: 0.99998
203 + Stage 6: FIRResponseStage from COUNTS to COUNTS, gain: 1##
204 +
205 +
206 +For the most part, the data logger response essentially flat when the samplerate output is set to 100 Hz or less and for seismological purposes is likely to be impossible to detect below 20 Hz regardless.
207 +
179 179  Instrument response can be downloaded from IRIS [[Nominal Response Library>>https://ds.iris.edu/ds/nrl/]] if need be, or [[directly from us>>http://auspass.edu.au/data/logger_response]] , or by downloading the response of an equivalent sensor at AusPass (e.g. get_stations(level='response') ).
180 180  
181 181  
... ... @@ -188,7 +188,7 @@
188 188  [[Amplitude and phase response for ANU logger at 1000 Hz>>image:ANU_1000hz_response.png||data-xwiki-image-style-alignment="center" height="367" width="489"]]
189 189  
190 190  
191 -[[Huddle test comparing a Trillium Compact 120 + TerraSAWR vs a Trillium Compact 120 + Nanometrics Centaur (M8.AUANU)>>image:TC120_ANU_vs_CENTAUR.png||data-xwiki-image-style-alignment="center"]]
220 +[[Huddle test comparing a Trillium Compact 120 + TerraSAWR vs a Trillium Compact 120 + Nanometrics Centaur (M8.AUANU) at 100 Hz>>image:TC120_ANU_vs_CENTAUR.png||data-xwiki-image-style-alignment="center"]]
192 192  
193 193  = ANU TerraSAWR (Gen 3, FW 3.5a, 2014- current) =
194 194  
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237 237  (% class="box" %)
238 238  (((
239 239  = TerraSAWR Specs =
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284 284  [[image:LPR battery.jpg]]
285 285  )))
286 286  )))
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287 287  )))