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Changes for page ANU Seismic Data Loggers

Last modified by robert on 2025/08/08 16:09
From version 61.1
edited by robert
on 2025/08/07 16:41
Change comment: There is no comment for this version
To version 62.1
edited by robert
on 2025/08/08 16:04
Change comment: There is no comment for this version

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171 171  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 +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.
174 +
173 173  //(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.)//
174 174  
175 -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.
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
176 176  
177 -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.
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 + Stage 8: FIRResponseStage from COUNTS to COUNTS, gain: 1##
178 178  
192 +
193 +However, if retrieving from AusPass or IRIS, the 2nd "sensor gain" stage is combined with the logger gain. This has no affect, but will be one stage short:
194 +
195 +##Channel Response
196 + From M/S (Velocity) to COUNTS ()
197 + Overall Sensitivity: 3.9546e+08 defined at 1.000 Hz
198 + 6 stages:
199 + Stage 1: PolesZerosResponseStage from M/S to V, gain: 754.3
200 + Stage 2: CoefficientsTypeResponseStage from V to COUNTS, gain: 524288
201 + Stage 3: FIRResponseStage from COUNTS to COUNTS, gain: 1
202 + Stage 4: FIRResponseStage from COUNTS to COUNTS, gain: 1
203 + Stage 5: FIRResponseStage from COUNTS to COUNTS, gain: 0.99998
204 + Stage 6: FIRResponseStage from COUNTS to COUNTS, gain: 1##
205 +
206 +
207 +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.
208 +
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') ).
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238 238  (% class="box" %)
239 239  (((
240 240  = TerraSAWR Specs =
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292 292  )))