Model QM-4.5-ADXL103 Single-Axis, Strong Motion, Accelerometer System.

Welcome to The Inexpensive Seismometer Project, an attempt reduce the cost and complexity of amateur seismic systems.

This page is about my project to build simpler and less expensive amateur short period seismometers by using microprocessors and other new chips, such as switched capacitor filters. Short period seismometers are useful for detecting and analyzing local seismic activity (within a few hundred miles or closer). For more general information on other types of seismometers and links to web resources, see my main seismometer page. Click here for information on my long period system.

November 2005 QM system board status: Beta test systems have been sent to Panama, Los Angeles, Nevada, Spokane, and Portugal.

Here is my latest QM-4.5-ADXL103 strong-motion, single-board, single-channel accelerometer design :

• Sensor: ADXL103 single-axis 1.5g accelerometer chip with lower noise than ADXL105 or ADXL202.
• QM-4.5 board is designed to work with one ADXL103 or one Mark Products 4.5 Hz geophone.
• ADXL103 is mounted on a DIP carrier board that plugs into the opamp socket.
• Plugging in ADXL103 disables geophone and replacing opamp enables geophone.
• ADXL103 integrated amplifier produces 1 volt/g over +/-1.5 g range
• QM-4.5 low pass filter chip MAX4701 is set to pass 0-4.5 Hz.
• QM-4.5 board 16 bit adc resolves acceleration 0.076 mg over +/- 1.5 g range
• QM-4.5 rms noise level is 3.6 adc units, or 0.27 mg.
• A QM-4.5 pcb board is being debugged, but some prototype circuit boards are hand wired.
• A diecast aluminum enclosure (Hammond 1590)is provided for EMF and thermal shielding.
• Shielded 9' cable with connector connects the geophone to the circuit board.
• Geophone amplification is single stage, low noise, 1900x voltage.
• Geophone amplifier chip: AD8626 auto-zero, low noise, precision, rail-to-rail output, op amp.
• Geophone and accelerometer Low-pass filter: 8 pole Bessel filter lowpass cutoff set to 4.5 Hz.
• Geophone and accelerometer filter chip: MAX7401CPA 8th order, lowpass, Bessel, switched capacitor filter.
• Microprocessor: 8 bit, 4 mHz PIC14000 with 16 bit A/D, replace chip to upgrade software.
• A to D: PIC14000 integrated 16 bit adc covering a 0-4.95 volt range.
• Microprocessor software: burned into PIC14000, controls A to D, time integration, etc.
• Voltage regulator: micropower LP2950ACZ-5.0 with very low dropout voltage.
• Serial output rate is adjustable (by DIP switch) from 8 to 35 samples per second.
• Serial output 10' cable with DB9 female connector for PC COM port.
• Serial extension cables (DB9 M/F) up to 100' are usable for remote sensor locations.
• Serial output rate is 9600 baud, 8N0.
• Serial output ASCII records vary from -32767 to +32767, where 0 is zero velocity/acceleraton.
• Power is derived from the PC serial port, and the board turns on when connected.
• Power on board is single-supply @ 5 volts, current is less than 4 ma @ 5 volts.
• LED Power On indicator blinks at sampling rate.
• You download Amaseis (freeware) for data logging, helicorder display, data export, etc.
• You download AboutTime (optional/freeware) for time synchronization via Internet.
• You download RighTime (optional/free trial) if you need to adjust Win95/98 PC clock.
• You download WinQuake (optional/free trial) for seismic data analysis.

• You can pay by check, money order, credit card or PayPal. The QM-4.5-ADLX105 strong motion accelerometer prototypes can also be used as short period seismometers if you have a 4.5 Hz Mark Products geophone. There is a diecast aluminum enclosure around the circuit board, accelerometer and or geophone. To start recording, all you need is to download the Amaseis software and plug the QM-4.5-ADXL105 serial cable into your PC serial port.

  OPTIONS: You may want to consider a serial (DB9 M/F) extension cable if you want to bury the geophone to reduce background noise pickup. The QM-4.5-ADXL105 has a built-in serial cable that is about 10 ft long, and a cable to the geophone that is about 6 ft long. I have some serial extension cables that are 10 ft ($10), 25 ft ($20), 50 ft ($30), and 100 ft ($50) long.

  MAIL ORDERS: For a QM-4.5-ADXL105 strong motion seismometer that is ready to run with the free Amaseis computer program, you will need both the electronics board and an ADXK105 accelerometer chip on a DIP carrier board:

  PRICES
  ___Complete accelerometer unit in case for RF and thermal shielding:
  1 QM-4.5-ADXL103 Assembled/tested pcb, diecast enclosure, 10 ft cable, QM-ADXL103 on DIP adapter @ $149
  ___Parts/Options:
  1 QM-4.5 Assembled/tested pcb, no enclosure, no ADXL103, with 10 ft cable @ $99
  1 QM-ADXL103 accelerometer chip mounted on a carrier DIP board, plugs into QM-4.5 @ $30
  1 L-15B Mark Products 4.5 Hz Geophone (used but working), works in QM-4.5 when ADXL103 not plugged in @ $40
  ___Shipping:
  1 Shipping within the US is by USPS Priority Mail @ $5
  --------------------
  

  To order, mail a check or money order payable to Infiltec to:
  

  Infiltec Seismometers
  PO Box 8202
  Falls Church, VA 22041-8202
  
  Phone: 703-820-7696
  Fax: 703-671-9350
  

  Email: .

  CREDIT CARD/PAYPAL ORDERS: you can order by credit card (MV/VISA/AMEX) pr PayPal by printing out our Order Form(text) or Order Form(Word) and faxing it back to 703-671-9350.

  INTERNATIONAL ORDERS: determine your shipping cost from the USPS International Shipping Calculator. Select your country, assuming a single box less than 1 ft3 in size and a shipping weight of two pounds (1 kg) per seismometer. Let me know if you want to make other shipping arrangements.

  PAYPAL ORDERS: (for orders shipping within the US only)

  AVAILABLITY: It generally takes about two-four weeks to build and test your system, after I receive your order.

  WARRANTY: Your money back if you are not satisfied for any reason. Just return the system in reasonable shape for a full refund. If the system is defective, please ship it back for a no-charge repair.

  TUNE UP: Any time I make improvements to the microprocessor firmware and/or circuit, you can return your board for these upgrades for $30.

  LATEST IMPROVEMENTS:
  051101: laid out proto QM-4.5 board and had some made - debugging
  051029: replaced ADXL202 by ADXL103 for lower noise and simpler interface with QM-4.5 pcb

• Provide do-it-yourself kits including circuit board and parts.
• Develop data logging software that automatically records significant events.

• Do you have suggestions? Please send them to .