ANU Seismic Data Loggers

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ANU has designed and built three generations of seismic data recorders, two of which (the small yellow TerraSAWR and the larger beige LPR-200) are still in use today. Despite their contrasting appearance, they both use the same software, data cards, and have the same instrument response.

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= Data Card Formatting and Information =

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Both the TerraSAWR and LPR-200 require SD Cards to be formatted in FAT32 filesystem. For 64Gb cards it can be difficult to format in FAT32, but [[software >>http://auspass.edu.au/field/fat32cardformatter.exe]]is available. ANU recommend SanDisk Extreme 150 mb/s cards in either 32 or 64Gb size. We strongly discourage using cards larger than 64Gb, and in general smaller cards are less likely to fail. We have also found that "adapter" cards (e.g. SD to microSD) are prone to having write issues and **strongly** advise against them.

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The loggers can be "pre-programmed" with information (e.g. site name, sampling rate, etc) or they can be programmed in the field using the buttons on the logger. To pre-program the cards you simply edit a text file (named "[[ANUSRSetup.txt>>http://auspass.edu.au/field/ANUSRSetup.txt]]" for the LPRs, or "[[tSAWRSetup.txt>>http://auspass.edu.au/field/tSAWRSetup.txt]]" for the TerraSAWRs) and place it in the root directory on the SDCard. When the logger boots up, it will parse and load this information.

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The format for ANUSRSetup.txt / LPR200s will be a single line of text that looks like this:

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{{{XXX195G0100010034864 2 }}}

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corresponding to site XXX19,

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network 5G,

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sample rate 0100, (e.g. 100 hz)

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"gps interval" 01 (once per hour~-~- don't change),

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start mode (always 0),

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stop mode (always 0),

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seismometer type (3 = broadband (+/- 20V), 1 = shortperiod (+/- 5V),

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and seismometer serial number (4864).

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the 2 at the very end is for "start recording on power"

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and is vital to have this set so the logger will resume recording on its own if it experiences a power cycle. (# of blank spaces before this doesn't matter)

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the TSAWRs are a bit shorter as they don't have an option to set the "gps sync"

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{{{SITE1XX02500039999 2}}}

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which would set up a Trillium Compact with serial 9999 named XX.SITE1 at 250hz sample rate.

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Here is a general guideline for how much data you can expect to fit on a card:

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{{{ 64Gb card: 245 days @ 250hz or 610 days @ 100hz

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32Gb card: 122 days @ 250hz or 305 days @ 100hz}}}

= LogFile Conversion Script =

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Both the TSAWR and LPR-200 write logging information as a binary "dat" file which includes GPS time syncs, temperatures, battery power, and position. To convert them into ASCII you can read, use [[THIS PYTHON SCRIPT>>http://auspass.edu.au/field/anusr_log.py]].

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= Instrument Response =

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Both the TerraSAWR and LPR-200 use the same ADS1281 analog-to-digital converter chip and are designed to have identical instrument response. Depending on the output sample rate (e.g. 100 Hz, 250 Hz, 500 Hz, 1000 Hz) amplitude response is consistently flat up to ~~100 Hz but phase response can vary above 1 Hz at 100 Hz (or 10 Hz at 250 Hz).

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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.

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Another important thing to note is that the group delay associated with late stage FIR filters is **automatically applied in the logger**, hence there is no need to apply this in the response. These tend to max out at 0.124 seconds for most output sampling rates (0.062 s for 100 Hz).

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Instrument response can be downloaded from IRIS-NRL (v2) if need be, or by downloading the response of an equivalent sensor at AusPass (e.g. get_stations(level='response') )

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= ANU TerraSAWR (Gen 3, FW 3.5a, 2017?- current) =

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