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Changes for page ANU Seismic Data Loggers

Last modified by robert on 2025/06/30 19:28
From version 49.1
edited by robert
on 2025/06/27 16:42
Change comment: There is no comment for this version
To version 50.1
edited by robert
on 2025/06/30 18:12
Change comment: There is no comment for this version

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... ... @@ -165,10 +165,10 @@
165 165  
166 166  = Instrument Response =
167 167  
168 -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 various stages. First via a 5th order SINC filter, then another 32x via 3-4 2x or 4x FIR filters. If the output is below 250 Hz, a final "pure" /5 decimation is done without any sort of FIR filter.
168 +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.
169 169  
170 170  {{info}}
171 -All SINC and FIR filters are performed internally within the logger and all phase delays are accounted for. Thus, the FIR coefficients and delays are not needed/given in the response information.
171 +The Stage 3 SINC coefficients (600+) during the initial 1024k > 16k decimation were left off as they slowed down the process x10 and contribute very little (< 0.3 db, < 0.31 ms) to the end result
172 172  {{/info}}
173 173  
174 174  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.
... ... @@ -212,6 +212,7 @@
212 212  
213 213  
214 214  
215 +
215 215  (% class="box" %)
216 216  (((
217 217  = TerraSAWR Specs =