The Inexpensive Infrasound Monitor Project.

Detailed information on a low-cost design for a microbarograph that
can detect and monitor infrasound (sound under 20 Hz). This design makes
infrasound detection available for schools, businesses and amateurs.

rainbow line

INTRODUCTION:
Welcome to The Inexpensive microbarograph Project! This infrasound monitor project is designed to make it possible for schools, businesses and amateurs to detect, measure and monitor the infrasound in their environment. See for latest page updates.
PROJECT STATUS:
- CURRENT STATUS:
  - IN PRODUCTION: The Infiltec Model INFRA20 Infrasound Monitor is now available for worldwide shipping.
    - VIEW THE LAST 24 HOURS OF INFRA20 REAL-TIME INFRASOUND MONITORING:
      
      click on Image for larger view
      
      This infrasound display is updated every 5 minutes and is generated by an INFRA20 that runs 24/7 inside the Infiltec factory warehouse. The display was generated by the free AmaSeis seismic data logging/display software and the display updates are by Fling FTP software. You can set up a similar online display with your INFRA20 using the same software. Click on display image to enlarge and update. Even though the INFRA20 is inside a building, it can detect the infrasound outside the building. Each horizontal line covers 1 hour.
      - The oval shaped infrasound peaks (about 3 minutes long) come from freight trains as they pass within about 100 meters several times per day.
      - The rectangular infrasound peaks (about 10-50 minutes long) come from a gas space heater fan in the factory.
      - The short infrasound spikes can be caused by doors in the factory being opened and closed.
      - Wind is the most common infrasound noise, and it generally peaks during the daylight hours. You can check the local weather and wind here.
      The hours on the vertical axis are in Universal/GMT time, +4 hours ahead of local USA EST. The data logging time base is corrected within milliseconds by the free program NetTime.
    - GRAPH OF INFRA20 INFRASOUND INTENSITY FROM A SPACEX ROCKET LAUNCH AND LANDING:
      
      click on Image for larger view
    - VIDEO & AUDIO OF 100x SPEEDUP OF INFRA20 INFRASOUND FROM A SPACEX ROCKET LAUNCH AND LANDING:
    - HOW TO ORDER:
      - Option1: FILL OUT OUR ORDER FORM AND SEND IT TO US (form includes our most complete set of ordering options)
        Compute the cost of your order on the form. You can pay by credit card, wire transfer, or PayPal to infiltec@gmail.com.
        Factory Address: Infiltec Instruments, 108 South Delphine Avenue, Waynesboro, VA 22980, Phone (540) 943-2776, Fax (540) 932-3025.
      - Option2: CALL INFILTEC at 1+ (540) 943-2776 Weekdays 7 AM - 4 PM Eastern USA Time.
      - Option3: ORDER FROM eBay INFRA20 or eBay INFRA20-LED (eBay may have the best international shipping options)
        Note: for simple shipping to Russia, Kazakhstan, Belarus or Ukraine, please consider setting up an account with QWINTRY AIR
      - Option5: ORDER FROM Amazon
    - PICTURES OF THE INFRA20:
    - Complete Infiltec INFRA20 Infrasound Monitor hardware ready to run (click on image to enlarge).
    - Infiltec INFRA20 Infrasound Monitor label with Quick Start Instructions (click on image to enlarge).
  - APPLICATIONS OF THE INFRA20:
    - Wind turbine monitoring.
    - Animal monitoring, including elephants, hippos, rhinos, giraffes, tigers, alligators, certain birds, etc.
    - Earthquake and tsunami monitoring.
    - Bolide or detonating fireball meteor monitoring.
    - Volcano monitoring.
    - Avalanche monitoring.
    - Thunderstorm, lightning and severe weather monitoring.
    - Sonic boom monitoring.
    - Explosion monitoring.
    - Aurora monitoring.
    - Paranormal investigations.
    - Rotating equipment monitoring.
    - Sick building analysis.
    - Environmental assessments.
    - Microbarom monitoring.
    - Helicopter monitoring.
    - Tornado monitoring.
  - FEATURES AND BENEFITS OF THE INFRA20:
    - 10 second hardware setup! Take it out of the shipping box, plug it into your PC, and recording starts. (This assumes that AmaSeis seismic software (1.3mb exe download) is installed and running)
    - Works with free AmaSeis seismic Windows software that provides data logging, 24 hour display, spectral analysis, bandpass filtering, etc.
    - No assembly ever required.
    - No damping adjustments ever required.
    - No external power supply ever required.
    - No leveling adjustments ever required.
    - No alignment ever required.
    - No adjustments for moving ever required, just pick it up and move it.
    - No adjustment of internal electronics (amplifier, filter, digitizer, power supply) ever required.
    - Practically indestructible to damage caused by shock, vibration, shipping & handling.
    - One enclosure contains everything: sensor, amplifier, filter, digitizer, power supply.
    - Metal enclosure shields electronics against noise from nearby electromagnetic interference.
    - High digital resolution (16 bits) keeps large and small infrasound events on scale.
    - Elliptic low-pass filter cutoff (8 pole) allows slow sampling output (50 sps) without aliasing.
    - Microprocessor firmware adjusts for component drift due to temperature changes, aging, etc.
    - Very low power (under 0.05 Watts) operation. Designed to operate continuously 24/7.
    - Connects to PC DB9 serial port, or a USB port through a USB-Serial DB9 adapter.
    - Works on Windows 98/XP/Vista/7/8/10 PC via AmaSeis logging data 24/7 in background. You can use your PC for other jobs while AmaSeis is running.
  - SPECIFICATIONS FOR THE INFRA20
    - Performance: Resolution is 0.001 Pascals (0.01 microbar or 0.0075 millitorr) over the range of + or - 25 Pascals (250 microbars or 187.5 millitorr).
    - Mode of Operation: Microbarograph design with solid-state differential pressure sensor and high-pass pneumatic filter.
    - Output: Serial output formatted for AmaSeis free seismic software (1.3mb exe download) , RS232 9600 baud N81 ASCII, 50 samples/second.
    - Frequency Pass-Band: 0.05 Hz to 20.0 Hz bandwidth digitized and stored on hard drive by AmaSeis at about 10 megabytes per 24 hours of operation.
    - Temperature Range 40 to 90 F (4 to 32 C) with no adjustments required. Internal firware automatically adjusts for drifts. Requires constant temperature during operation that can be provided by insulation such as a small cooler.
    - Housing: Diecast aluminum box encloses all electronics and sensor, 6.024x3.268x1.988 inches (153x83x50.5 mm). Shipping weight 2.2 lb (1 kg).
    - Computer Connection: 15 ft (4M) serial cable (up to 100 ft (30M) extension optional) connects to PC DB9 connector or USB-Serial DB9 adapter.
    - Adjustments: No leveling, alignment, damping, gain, zeroing, etc adjustments required.
    - Power Supply: No external power supply required, all power (under 0.05 Watts) is supplied by PC serial port through the serial cable connected to the PC.
    - Digital Processing: 16 bits voltage resolution from internal digitizer, 50 sample/second ASCII output, firmware adjusts for component drifts.
    - Lowpass Filter: Very steep analog 8 Pole elliptic filter with 20 Hz corner frequency for anti-aliasing.
    - Software: Windows PC based seismic data logging and analysis software AmaSeis available online for free download. Includes spectral analysis and bandpass filtering functions.
    - Computer Requirements:PC running Windows (98/XP/V/7/8/8.1/10 32 or 64) can run AmaSeis in backgound while doing other tasks. Hard drive that can store 10 megabyte/day during 24/7 operation. DB9 serial port or USB port for supplied USB-Serial adapter.
  - SAMPLE DETECTIONS BY AN INFRA20 SYSTEM:
    - Click here for a typical 24 hour AmaSeis display on a calm day. The red outline is around a typical helicopter infrasound signal with two other helicopter signals next to it. The green outline is around typical wind noise data. And the blue outline is around a typical spike signal for a door closing in the adjacent building.
    - Here is the red outline helicopter infrasound signal expanded AmaSeis display. Note the peak amplitude is about 1000 counts which corresponds to 1 Pascal (10 microbars) because the INFRA20 resolution is 0.001 Pascal (0.01 microbar) per count.
    - Here is the AmaSeis power spectra of the red outlined helicopter infrasound signal. The power peak is around 17 Hz but it is spread out because of +/- doppler shift as the helicopter goes by. Note the steep roll off of the 8 pole elliptic 20 Hz low pass filter used in the INFRA20 for anti-aliasing.
    - Other recent infrasound source detections by Infiltec include: freight trains, microseisms, compressors, and wind turbines.
  - UNDER DEVELOPMENT: A Portable Infrasound Generator .
    - Precise digital tuning within the 8 to 20 Hertz output in the Infrasound Range.
    - Controlled by a built-in variable frequency generator and driven by a powerful subwoofer amplifier
    - Powered by either house current 110-240 VAC or 12 VDC car battery
    - Portable by truck or van
    - Design follows Helmholtz resonator principles
    - Inexpensive compared to other speaker designs
    - Driven by powerful subwoofer speaker
    - Potential applications include: music augmentation, classroom/public demonstrations, evaluations of effects on people and animals, repelling birds, propagation studies, paranormal research, etc.
    - Contact Infiltec for latest development status.
    Picture of prototype during testing (click on image to enlarge)

FAQ for Infiltec INFRA20 Infrasound Monitors
- What kind of computer do I need for microbarograph data logging?
  We have free data logging software for Windows, MAC, and Linux computers. Almost any PC with Windows XP to Windows 10 (32 or 64) will run the free AmaSeis free seismic software (1.3mb exe download) . We have tested it on Windows XP, Vista, 7, 8.0, 8.1 and 10 and 32 or 64 bits. You can still use other Windows programs while the AmaSeis data logging continues. You will need to have a connection to the Internet to run the internet time correction software. Most computers today do not have hardware serial COM port, so we provide a USB-Serial adapter cable that can create a virtual serial COM port from a USB port. There is a new free version of AmaSeis called jAmaSeis that works with Windows, Apple computers and Linux computers. We are working on a Raspberry Pi system with Raspian and jAmaSeis that would replace the requirement of using a PC or MAC to log INFRA20 data.
- How can I prevent my AmaSeis program from stopping every few days?
  Here are some suggestions listed in order of priority:
  1. to keep AmaSeis running 24/7 you MUST keep the AmaSeis 24 hour "helicorder" display running full screen, and NOT reduce it to the task bar by clicking on "-" at the top right of the PC screen for more then a few minutes. If you are running another program while AmaSeis is running, then you can cover up the AmaSeis screen. If you do reduce AmaSeis to the task bar, then it may run for a day or two, but it may halt randomly because it can not keep up with the serial data.
  2. You should also try setting DECIMATE=9 from the Helicorder menu. When the helicorder 24 hour data screen updates on the hour, it has to rewrite the past 24 hours of data, and there will be less load on the PC processor because DECIMATE=9 will only redraw every 9th data sample. You can experiment with other values of DECIMATE to see how they effect your data display. Note that all the AmaSeis display parameters like DECIMATE, GAIN and the filtering parameters DO NOT effect the data recording because AmaSeis always records the full INFRA20 bandwidth. So you can go back and look at previously recorded data with different decimate, gain and filter parameters.
  3. Newer PCs with more recent Windows versions, faster processors, more memory, and faster drives generally give better AmaSeis performance. AmaSeis works well with Windows 10. We have multiple instances of AmaSeis working simultaneously on one Windows 10 PC. However, we have also had single AmaSeis instances working 24/7 on Windows XP PCs.
  4. There is a new version of AmaSeis called jAmaSeis (the j is for java), and it is available for Windows, MAC, and Linux. It seems to run well, but we do not have as much experience with jAmaSeis as with AmaSeis. You can download a free copy of jAmaSeis from jAmaSeis download
  5. It sometimes helps to do some windows "cleanup" to make sure that your Windows is running as smoothly as possible. Especially if the PC has been running for a long time with no software maintenance. You might try: A).a registry cleaner like the free "Wise Registry Cleaner" B) a file and registry cleaner like the free "CCleaner" C) a file defragmenter like the free "MyDefrag" YMMV.
- How can I make AmaSeis time accurate to a few milliseconds?
  You can make the time base on your computer more accurate by downloading and running a free program that resets your PC internal clock to universal internet time every 20 or 30 minutes. Try NetTime download (I am using this), or NIST Internet Time Service download Note that AmaSeis only checks the PC time on the hour, so the closer to the hour you can correct it, the better. Also you must have an internet connection to use these programs.
- How can I find the COM port that Windows creates when I plug in the USB-Serial adapter?
  When you plug in the USB-Serial adapter, Windows will search for a software driver, and if you are connected to the internet and you have Windows 7 or newer, then Windows will find the latest version of the Prolific adapter driver. However, if you have an earlier version of Windows or you are not connected to the internet, then you will have to load the Prolific driver from the CD that is supplied with the INFRA20.
  Most of the time, the new COM port will be 1,2,3 or 4; so you can enter each of these numbers into the AmaSeis COM port window, and then restart AmaSeis to see if the COM port error message goes away.
  If that does not work, then to find the COM port that has been created by the driver you can also use the free terminal program TeraTerm
  When you run TeraTerm, click on the "serial" button, and then look in the list of COM ports for one that says "Prolific". Note that the adapter has to be plugged in when you run TeraTerm for the COM port to appear. When you click on the prolific driver you will see a stream of data if the USB adapter is connected to the INFRA20.
  To set AmaSeis to the correct COM port, start AmaSeis and click OK on the "cant find COM port" message, then click OK on the "no data" message. Then click on the "settings" menu item and go down and click on "COM port". Then enter the COM port number you found with TeraTerm, and then restart AmaSeis so that it will save the new COM port number as the default. When you restart it should start running on data from the INFRA20.
  One other thing. You also need to set the DEVICE in the "settings" menu. Select the INFILTECQM1 in the device settings, so that AmaSeis will know what kind of seismometer it is processing.
- How do I use the tubing that comes with the INFRA20?
  You do not have to use the tubing at all. It is optional.
  You can use the tubing when the location you want to test is different than where the monitor is. For instance, if you have the monitor inside, but you want to test outside, then connect the tubing and run it from inside to outside. Try to shield the open end of the tube from wind to reduce wind noise.
  Another reason to use the tubing is to connect the INFRA20 to a multiport wind averaging system to reduce the wind induced infrasound background noise. Here is a picture of a professional multiport wind averaging system in Greenland from the Wikipedia article on infrasound. We have made smaller portable wind averaging arrays composed of a multiport array of flexible tubing terminated with fish tank airstones, or with inverted pie plates.
  Generally we have found that outside infrasound can be detected just about as well with the monitor inside a building and no tubing attached, as with the monitor outside with no tubing, or with the monitor inside with the tubing attached and running to the outside. Of course when you run the monitor inside you will detect door openings/closings and any fans operating inside the building. Often running the INFRA20 inside with no tubing connected will give you some wind shielding that reduces the infrasound background noise compared to running outside with no wind averaging.
  Here is a live 24 hour infrasound plot from an INFRA20 running on AmaSeis software inside the Infiltec factory warehouse, with no tubing attached. The factory is about 100 yards from a busy freight train bridge, so you can generally see infrasound peaks from the trains passing by every few hours. You can also see lots of spikes during work hours from door openings/closings in the building. In general the night time is low wind, and our factory building is unoccupied then, so the infrasound background noise levels tend to be lowest then. When the local wind is zero and there is a storm at sea somewhere on the East coast, this INFRA20 in Waynesboro, VA about 250 miles inland can detect the microseism infrasound signal at about 0.2 Hz. On this display the unoccupied night time is from about 8PM local EDT (00 UT) to 5AM local EDT (09 UT). Note that AmaSeis displays are in Universal Time (UT).
- What is the INFRA20 serial output data format?
  The INFRA20 putput data format is serial 9600 bps, 8N1, ASCII records, no hardware control. Each ASCII record is terminated by LF and CR characters (10 and 13). Records range from +32767 to -32767 and zeros are added to keep the record length constant, eg. +10 is sent as +00010. The sampling rate is about 50 records per second. Every 24 hours of operation, AmaSeis stores on your hard drive about 10 megabytes @ 50 records per second.
- What is the INFRA20 calibration?
  Each record count is approximately 1/1000 Pascal sound pressure. So 1000 counts is 1.000 Pascals. To convert to dB (SPL) you can use the online calculator. For example, 1 Pascal is 93.98 db (SPL). This calibration is based on the specifications of the INFRA20 components and is probably correct within 20%. We are working on a more precise calibration and certification proceedure.
- What is the minimum infrasound signal that INFRA20 can measure?
  The INFRA20 electronic noise level is about 20 counts (20 mPa or 60 dB SPL) over the full bandwidth, and this can be measured by cross connecting the ports on the internal differential pressure sensor. The lowest ambient infrasound level over the full bandwidth that you can expect to record with the INFRA20 is about 30 counts (30 mPa or 63.5 dB SPL), typically during the middle of the night when the wind is calm and there are no nearby infrasound sources. The INFRA20 background noise level is low enough so that the microbarom peak at about 0.2 Hz can sometimes be detected above the ambient noise when the wind is calm.
- How sensitive is the INFRA20 to changes in elevation?
  If you move the INFRA20 up or down by 1 meter, it will register a change of 12 Pascals, or 12,000 counts. This is because the INFRA20 is essentially a "leaky barometer" and it must be kept stationary in the vertical direction in order to avoid false infrasound signals. The INFRA20 would probably not work well in a moving vehicle, and it would not work very well if it was being carried, for this reason.
- How sensitive is the INFRA20 to temperature?
  The INFRA20 mechanism contains a closed volume connected to a very small leak. If the temperature of this volume changes, then a pressure will be created inside this volume that will equalized with atmospheric pressure by airflow through the leak. This pressure will interfere with the interpretation of the infrasound signal. Therefore is it important for any temperature changes to the INFRA20 mechanism to be slowly varying, so that the device can compensate for these pressure changes. The INFRA20 software is designed to compensate over minutes to slow temperature drifts, but not for large temperature changes over short periods. If the INFRA20 is inside an occupied building, then the temperature changes will probably not be a problem unless the device is in the path of a heater or cooler. Similarly, if the INFRA20 is outside then slow temperature changes will generally not be a problem. If you want to shield the INFRA20 from larger temperature changes, then it can be placed inside an insulated box, like a lunch cooler, with thermal mass like water bottles to keep the temperature changes slow. For permanent outdoor installations, burying the INFRA20 in an underground vault with moisture protection may provide very stable temperatures.
- How do you reduce infrasound wind noise?
  Wind is the most common source of infrasound background noise, especially below 2 Hz. The nuclear test band treaty infrasound monitoring installations have extensive spatial wind noise averaging systems consisting of many open sensor pressure ports spread out over a wide area and manifolded together at the monitor input. See the Wikipedia article on infrasound for a picture of an infrasound wind noise averaging array. If the wind noise is uncorrelated at each port, you should expect a noise reduction of about 1/squareroot(number of ports in array). Other pictures of wind noise averaging systems can be found that use porous hoses, forests, piles of stones, etc. Infiltec is working on designs for portable wind averaging arrays for the INFRA20 that use inverted metal dishes for ports, or fishtank bubbler stones. Note that INFRA20 measurements can often be made from inside buildings where the buildings themselves provide some measure of wind averaging. Similarly measurements can be made from inside stationary automobiles with windows cracked open to provide some wind averaging.
- Can the INFRA20 be used to detect infrasound from wind turbines?
  Yes, the INFRA20 is in use worldwide to record and analyze wind turbine infrasound. This type of infrasound appears to be generated by the turbine blades passing by the support structure, and this blade-pass generally occurs about every 1.5 seconds, resulting in narrowband spectral harmonics with frequencies that are multiples of about 0.7 Hz: 0.7 Hz, 1.4 Hz, 2.1 Hz, etc. This infrasound signature spectrum can often be monitored from inside buildings. Infiltec can provide custom modifications to the INFRA20 so that other acoustic recorders and data loggers can access the unfiltered differential pressure sensor voltage data. This allows for the INFRA20 use with any acoustic analysis software and hardware.
- Can the INFRA20 be used to detect infrasound from meteors?
  We do not know of any INFRA20 meteor monitoring as of March 2016. But the INFRA20 should be sensitive enough if it is combined with a suitable wind averaging array. Here is the description of a university meteor infrasound system that could probably be built with an INFRA20 monitor. It utilizes a porous hose wind noise averaging system that is installed in a forest for additional wind noise averaging. Note that if multiple INFRA20 are used for direction calculations, then custom software may be required to calculate direction. Please let us know if you set up a meteor infrasound system.
- Why does AmaSeis saftware sometimes indicate an INFRA20 sampling rate of ~50 samples per second (sps) and other times 16 sps?
  Make sure the AmaSeis software display ALWAYS indicates an INFRA20 sampling rate of ~50 sps when you are recording or analyzing data. 16 sps will cause analysis errors! The AmaSeis software needs to ALWAYS be running the INFRA20 and recording data when you are analyzing recorded data to keep the sampling rate at ~50 sps, or else AmaSeis will set the sampling rate to its default value of 16 sps. But 16 sps will will cause AmaSeis to calculate incorrect time and frequency data analysis! This is true even when examining data from the past from the AmaSeis recorded data base. Unfortunately the AmaSeis stored infrasound data base DOES NOT keep track of the INFRA20 actual sampling rate of ~50 sps, so keeping the INFRA20 connected to the pc and recording data will keep it at the correct sampling rate of about 50 sps. One way around this problem is to use your right mouse button to block and SAVE AS data segments of interest as .SAC format data files which will keep their correct sampling rate. You can open these .SAC files with the AmaSeis FILE OPEN command whether AmaSeis is recording INFRA20 data or not. You can send these SAC files to other AmaSeis users without worrying about the sampling rate changing.
- Why does AmaSeis software stop when my PC sleeps?
  When your computer sleeps you need to make sure that it never shuts down its processor or hard drive so that AmaSeis can keep data logging. But it is ok to shut off your display while AmaSeis runs.
  Go to the windows "control panel" find "power options" and then "edit options" and where it says "when plugged in"/"put computer to sleep" change that option to "never".
  Another way to make this change is to click on the windows start button, and type "power options" where it says "search programs and files" then it should show "power options" under "settings" and when you click on this, it will take you to the "edit plan settings" screen where you can select "never" sleep as your option.
  Note that another way that AmaSeis may stop recording occasionally is if you reduce the AmaSeis 24hour data display screen to the task bar. That seems to reduce the priority of the program so that the serial data input does not keep up and crashes AmaSeis (hours or days). Always keep the AmaSeis screen full screen, even if it is covered by another program's screen.
  Another way to reduce the AmaSeis processing load on your pc is to set the DECIMATE factor to about 9. At the start of each hour the 24hour display is redrawn and that redraw can increase the load on the cpu, but a decimate factor of 9 will only redraw every 9th data point, which speeds up the redraw without much change in the readability of the display. This may eliminate any unexplained AmaSeis dropouts that occur on the hour change.
- Will any USB-serial adapter work with the INFRA20?
  No. The USB-serial adapter that we supply with the unit is specially selected and tested to be capable of supplying the power necessary to run the unit.
  Most USB-serial adapters will not work because they can not supply the voltage and current necessary. The USB ports on all computers can supply the necessary power, but the problem is when the 5vdc from the USB port is converted to ~9vdc on some of the serial pins. Most adapters fudge on this. So the serial communications will generally work fine, but the unit will not have enough power to work reliably.
- Is anything missing from this FAQ?
  Please any suggestions for FAQ additions.
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INFORMATION FOR DO-IT-YOURSELFERS:
- USEFUL ONLINE ARTICLES:
  - Wikipedia Infrasound.
  - Infrasound Monitoring with a Microbarograph How to detect low frequency acoustic waves in the atmosphere.
  - Bringing together seismology and atmospheric sciences by Läslo Evers. Includes How can infrasound be measured? that shows pictures of a microbarograph, and its field installation with wind noise averaging by a porous hose array.
  - Infrasonic Symphony: The Greatest Sounds Never Heard from Science News, Week of Jan. 10, 2004; Vol. 165, No. 2 , p. 26.
  - Infrasonic from the Wikipedia.
  - NOAA Infrasonics Program
  - The Infrasound network (ISNet): Background, design details, and display capability as a 88D adjunct tornado detection tool.
  - ADVANCES_IN_INFRASOUND_TECHNOLOGY_WITH_APPLICATION_TO_NUCLEAR_EXPLOSION_MONITORING
- COMPONENTS
  - FILTER CHIP - MAX7401CPA 8th Order, Lowpass, Bessel, Switched Capacitor Filter low pass cutoff is configured with one external capacitor. I generally use a cutoff of 4.5 Hz for infrasonics. This chip requires 5 volts, single supply, 2 ma. The -3 dB filter cutoff (Fc2) in Hz is determined by Fc2=.380/C where C is the capacitance in ufd. For example, when C = .380 ufd, then Fc2 = .380/C = 1 Hz. The output of a switched capacitor must be filtered to remove the switching noise that peaks at 100 times Fc2 for this chip. I generally use an RC filter with an Fc3 that is about 1.5 times the chip Fc2. For 4.5 infrasound I set Fc3 to about 6.8 Hz.
  - A/D & PC INTERFACE CHIP - PIC14000-04/SP Programmable Mixed Signal Controller programmed with firmware that I wrote to configure IC pins for 16 bit A/D, and for serial output to a PC. This chip requires 5 volts, single supply, 0.5 ma. PIC 8-bit microprocessors can be programmed in firmware written in languages like PicBasicPro or CCS PIC C. You might be able to use a Basic Stamp BS1 or BS2 processor with an external A/D chip in place of the PIC14000. However, these processors and the a/d chip may use too much power to use the serial port as a source of power.
  - PCB LAYOUT AND NOISE REDUCTION - In order to get 16 good a/d bits, the circuit board must be laid out so as to minimize noise. All grounds must go to a central terminal point in a "star" configuration. All chips must have bypass capacitors on their power pins. In addition, the PIC14000 is programmed so that it goes to "sleep" during a/d operations to minimize digital noise in the circuit.
  - SAMPLING RATE - The 4 MHz PIC14000 can perform 16 bit A/D at about 60 samples per second (SPS) and these samples can be averaged in software for noise rejection. I have written the firmware to allow for a dip switch selection of averaging times from 4 SPS to 35 SPS.
  - SERIAL DATA FORMAT - Each output sample is an ASCII record terminated by LF and CR. The samples range from -32767 to +32767. This format can be read by the AmaSeis free seismic software (1.3mb exe download) data acquisition system. Output from Amaseis can be further analyzed by the WinQuake seismic event viewing software.
  - A/D CONVERTER OPTIONS - I use a microprocessor ADC to generate the serial data that Amaseis can process (the input ASCII records looks like +3, -2, +8 .....) but if you are not a microprocessor guru you can get a PC serial port data aquisition kit from DataQ. Their $24.95 DI-194RS Starter Kit is 4-Channel, 10-Bit, ±10V ADC. And the $149.95 DI-154RS Starter Kit is 4-Channel, 12-Bit, ±10V ADC. Note that the DataQ does not include a lowpass anti-alising filter. The Amaseis program has been modified to work with DataQ units.
  - TIME SYNCHRONIZATION You will need to get an accurate time reference to Coordinated Universal Time (UTC) (Greenwich England time without daylight saving time) since you want to know the arrival time of events within a second of UTC. Some folks hook their electronics to GPS or WWV radio systems but I am too cheap for that. I looked for some way to make my PC clock accurate to within a fraction of a second per week instead of its usual several seconds per hour of error. Here is what I came up with:
    - 1. Go to the Windows control panel under "Date/Time" and set your computer to GMT with no daylight savings time. Right now (winter) this is 5 hrs earlier than Eastern Time. It is not too much trouble to work with a PC set to this time.
    - 2. Go to NetTime download, or NIST Internet Time Service download and download the free program. This Windows program finds the reference time on the web and resets your computer clock to it. It even corrects for the travel time of the web packets. Set your clock within a few ms of UT with this program. If your computer has a dedicated web connection, you can set this software to reset the time every 10 or 15 minutes, and that keeps your computer clock in synch.
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  - USE OF SEISMIC DATA PROCESSING SOFTWARE FOR MICROBAROGRAPHS
    I found when I started my project in 2000 that most of the existing seismic data logging software was programmed to accept data from a few PC a/d boards, and most of the programs did not accept the ASCII data records that microprocessors can easily output. However I found one program that the author was willing to modify to accept simple ASCII records: the freeware program Amaseis. Here is all of the seismic software that I am have heard of that might be of interest to amateur seismologists. Please send me links to all the software I have missed.
    - AmaSeis free seismic software (1.3mb exe download) Alan Jones' seismic data logging software for Windows (free).
    - jAmaSeis IRIS seismic data logging software for Windows, Mac, Linux (free).
    - SEISAN, SEISLOG, SEISNET Observatories and Research Facilities for European Seismology software library. Article describing Seislog.
    - WinQuake Larry Cochrane's event viewing software for Windows ($35).
    - SDR Larry Cochrane's seismic data logging viewing software for Windows (free).
    - EMON Ted Blank's seismic data logging software for DOS (free).
    - SEISMOWIN Mauro Mariotti's seismic data logging software for Windows (free).
    - NetTime download, or NIST Internet Time Service download Windows time synchronization (Free).
    - SAC_to_PSN free software (60kb exe download) Conversion of AmaSeis SAC files to speeded up WAV audio files for Windows (free).
    - Raven Lite Conversion of Audio files to Waterfall display for Windows (free)
    - Please if you know some other software that I should list here.
  | Top | Introduction | Today | DIY | Components | Electronics | Order | Time | Software | FAQ | Links |
  - SOME LINKS I HAVE FOUND USEFUL
    - ACCELEROMETERS
      - Mesmsic thermal based accelerometer chip (comparable to Analog Devices)
      - Parallax accelerometer sensor uses Memsic digital output chip.
      - Analog Devices iMEMS®: Integrated Micro-Electromechanical Systems (ADXL105 & ADXL202).
      - ADXL202 Technologies and Applications.
      - ADXL202EB evaluation board (pdf) this packages the surface mount ADXL202 into a DIP package.
      - ADXL105 Technologies and Applications (improved version of ADXL05).
      - Crossbow packaged Analog Devices accelerometers.
      - PSN-L Email list comment of Scientific American article on using ADXL05 sensors for microbarograph measurements.
      - (pdf) Using the ADXL202/201 with the Parallax Basic Stamp Module to Speed Algorithm Development Analog Devices application note.
      - (pdf) Using the ADXL202 in Pedometer and Personal Navigation Applications Analog Devices application note.
      - Using the ADXL202 with a microcontroller.
      - Strong Motion Data on a ADXL05 Sensor quake data recorded from accelerometer.
      - ShakeMaps: Southern CA and Northern CA maps of acceleration magnitudes during recent quakes.
      - How to solder surface mount parts (like ADXL chips) using a toaster oven.
      - Brown Dog Component Adaptors DIP adaptors for surface mount chips.
      - Digikey: Surfboard adaptors to go from surface mount to through-hole (pdf file of catalog page).
      - ADXL 14 pin carrier board use my HP laser printer file to print circuit traces for a home brew board.
      - BasicStamp List messages about using the ADXL and surface mount chips.
      - DIY Air-pencil soldering iron how to make one for under $20.
      - Surface Mount Secrets
    - ELECTRONICS RESOURCES
      - Search enginz all about second hand book search, including book coupons.
      - Bookfinder compare used book prices.
      - BestBookBuys compare new book prices.
      - Amazon Art of Electronics by Horowitz and Hill (THE BIBLE!).
      - Amazon Active Filter Cookbook by Don Lancaster.
      - Amazon Troubleshooting Analog Circuits by Bob Pease (THE GURU!).
      - Amazon The Art and Science of Analog Circuit Design by Jim Williams.
      - Amazon Analog Circuit Design : Art, Science and Personalities edited by Jim Williams.
      - Amazon USB Complete: Everything You Need to Develop Custom USB Peripherals by Jan Alexson.
      - Amazon Serial Port Complete by Jan Axelson.
        CHIP SEARCH
      - FindChips
      - StockNet
      - QuestLink
      - ChipCenter
      - Need2Buy
      - USBid
      - CMB Components
      - Part Miner
        CATALOG/ONLINE SALES
      - DigiKey
      - Mouser
      - Hosfelt
      - Allied
      - Newark
      - Jameco
      - SimCo, OKW, SerPac, PacTec, Fibox inexpensive plastic enclosures.
        MANUFACTURERS/DATA SHEETS
      - Burr-Brown
      - Dallas Semiconductor
      - Linear Technology
      - Maxim
      - Microchip
      - National
      - Texas Instruments
      - Analog Devices
        MISC
      - Electronic Schematics on the Web
      - The Guru's Lair Don Lancaster's extensive links
      - GPS boards OEM board GPS for $79.
      - Newsgroups: sci.electronics.basics, sci.electronics.components and sci.electronics.design.
    - MICROPROCESSOR RESOURCES
      - Circuit Cellar magazine for embedded control applications.
      - Microchip PIC 8-bit microprocessors
      - PicBasicPro for programming PIC microprocessors, and email list with searchable archives.
      - microCode Studio PICBasicPro Edition.
      - CCS PIC C for programming PIC microprocessors (user exchange).
      - Peter H. Anderson resources on PIC embedded processor control
      - Parallax Basic Stamp processors - I got introduced to microprocessors here
      - DataQ DI-151RS Low Cost, 12 Bit A/D Serial Port Starter Kit As Sold By Radio Shack.
      - Newsgroups: comp.dsp, alt.microcontrollers.8bit and comp.arch.embedded.
      - PIC Tutorial: Understanding & Programming the PIC16C84 A beginners' tutorial.
      - PICLIST email list for people interested in the Microchip PIC.
    - MECHANICAL PARTS AND LAB EQUIPMENT SOURCES
      - ScienceLab lab equipment and chemical supply.
      - Rare-Earth Magnets sells new magnets.
      - ForceField sells recycled magnets
      - Hamilton Core Drill Bits neodymium magnets.
      - Grainger hardware distributor (magnets, etc.)
      - McMaster Carr hardware distributor (magnets, nuts, bolts, metals, etc.)
    - SOFTWARE
      - AktivFilter software for designing perfect active filters with real components.
      - AmaSeis free seismic software (1.3mb exe download) data acquisition system. Instructions for using Amaseis to analyze microbarograph data.
      - WinQuake microbarograph event viewing software. Instructions for using WinQuake to analyze microbarograph data.
      - Spectrogram 5.1 freeware audio spectrum analysis software.
      - FilterLab freeware tool that simplifies active filter design.
      - NetTime download, or NIST Internet Time Service download.
      - TaskInfo shareware that monitors the resources used by PC programs.
    - microbarograph
      - Seismology Bibliography and Book Reviews.
      - Bookfinder search for used books on reading seismograms etc.
      - BestBookBuys compare new book prices.
      - Amazon Earthquakes Bruce Bolt, 1999 4th Edition - great introduction.
      - Amazon Earthquakes and Geological Discovery by Bruce Bolt, Sci. Am. Library, 1993.
      - Amazon Modern Global Seismology Lay and Wallace, 1995.
      - Amazon Quantitative Seismology: Theory and Methods Aki, 2001.
        OTHER
      - SemismicNet Redwood City Public microbarograph Network (extensive information!)
      - Lehman the man who built the first Lehman microbarograph described in the July, 1979 Scientific American Magazine.
      - Lehman Manual (PDF format) "Instructions for Construction of Lehman microbarograph by Kelly Knight - May 2000.
      - Newsgroups: sci.geo.earthquakes and microbarograph.general.
      - AZPEPP Arizona - Princeton Earth Physics Project
    - GEOPHONES
      - Introduction to Geophones.
      - Infiltec QM-4.5 short period geophone microbarograph.
      - Geophone FAQ lists several manufacturers.
      - Geophone Model L-28 spec sheet (224k pdf).
      - Geophone Model L-15 spec sheet (205k pdf).
      - Walt's Geophone FAQs Selected PSN Geophone Postings.
      - Vault construction for your microbarograph by the Indiana University PEPP Program.
      - Vault construction for your microbarograph by the IRIS PASSCAL Program.
      - Improving a Geophone to produce a broadband microbarograph.
      - RT Clark sells used geophones.
      - Sercel parent company of Mark Products geophones.
      - eBay sometimes lists geophones.
      - NZ Geophone System Design shows circuit diagram and geophone mounting.
      - PSN equipment for sale may include geophones.
      - Simple procedure tests transducer EDN Magazine Design Ideas: March 1, 1996.
      - Remote 2-Wire Geophone Preamp Linear Technology design idea.
      - CablesToGo source for 25',50',100' extension serial cables for Infiltec geophone system (DB9, M/F).
    - PRINTED CIRCUIT BOARDS
      - BPECS: PCB Circuit Design Package (very inexpensive.)
      - CADSOFT: Eagle PCB Circuit Design Package.
      - Electronic Assembly News list of pcb sources.
      - AP Circuits quickturn prototype pcb's for under $100.
      - EP Circuits quickturn prototype pcb's can include solder mask.
      - Olimex Ltd. in Bulgaria lowest proto prices, 2 week delivery to US via air mail. (4"x6" PCB, double-side, WITH silkscreen + solder mask, for $26 plus $8 Airmail)
      - Advanced Circuits good prices on production runs of pcb's.
      - Pulsar great prices on production runs of pcb's.
      - NeatSite links related to PCBs.
      - Making Printed Circuit Boards book by Jan Alexson.
      - How to Make PCBs This is how I make them.
    - OTHER INTERESTING BUT LESS RELEVANT PAGES
      - SoPrePlaTec (pronounced "soapy platex") The Society for the Prevention of Plate Tectonics.
      - Sensors an awesome link page!
      - Vernier Science Hardware and Software for the Classroom.
      - Tinkers Guild Resources for Hands-on Science - sells CD of projects from the Scientifc American Amateur Scientist column.
      - Society for Amateur Scientists online projects and supplies.
      - Detecting Extraterrestrial Gravity by Shawn Carlson, from the January 2000 Scientific American Amateur Scientist Column.
      - Detecting Micron-Size Movements by Shawn Carlson, from the August 1996 Scientific American Amateur Scientist Column.
      - Earth Songs If humans had radio antennas instead of ears, we would hear a remarkable symphony of strange noises coming from our own planet.
      - Infrasound Monitoring with a Microbarograph How to detect low frequency acoustic waves in the atmosphere.
      - Crackpot Inventor original electronic devices, tools for clockmaking and repair, and a variety of other unusual handmade products.
      - Mad Scientist Network the laboratory that never sleeps.
    - SOME OF MY OTHER INTERESTS
      - Join the SETI@Home search for extraterrestrial intelligence. Here are my statistics. Please join my team Dickster.
      - Join the Einstein@Home search for gravitational waves. Here are my statistics. Please join my team Dickster.
      - Join the Predictor@Home predict protein structure. Here are my statistics. Please join my team Dickster.
      - Join the SIMAP@Home compute Similarity Matrix of Proteins. Here are my statistics. Please join my team Dickster.
      - Join the Rosetta@Home determine the 3-dimensional shapes of proteins. Here are my statistics. Please join my team Dickster.
      - My Business Page Infiltec Air Leakage Control.
      - My Other Link Page building science, books, travel, etc...
      - My fun page jokes and travel photos.
      - My Gold Prospecting Near Washington, DC Page.
      - My SID-GRB@home how to build a simple VLF radio receiver that can detect Gamma-Ray Bursts (GRB) from the edge of the universe.
      - My How to build an inexpensive seismometer for earthquakes worldwide.
  Please any suggestions or corrections to my microbarograph related links.
| Top | Introduction | Today | DIY | Components | Electronics | Order | Time | Software | FAQ | Links |
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