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Open Source Hardware
Forum Archaeology Resistivity Meter
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  • armp
  • archaeology resistivity meter
Related

Archaeology Resistivity Meter

kltm
kltm over 5 years ago

Hi I'm looking for ideas on an update to a resistivity meter for archaeology. The only published designs for diy were in 2 magazines. One was published in 1997 and the other in 2003. I have copies of both articles available. The reason behind this is the current high cost of available equipment, usually well beyond the reach of most archaeological groups. I've attached a basic block diagram. In the first magazine article the meter is very basic. It relied on the operators to write down the reading given as the survey was taken. Given that a normal survey grid is 20m x 20m and 1 reading is taken on every sq mtr there would be 400 readings to write down and then input into a program used to interpret the results. The later article is really an update to the first where a PIC has been added to record the readings. This again is prone to error, because eadings are taken manually by pressing a button.

I'm sure given the advances in electronics there must be better ways. 

 

 

 

image

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Top Replies

  • kltm
    kltm over 5 years ago in reply to michaelkellett +8
    Hi Michael This all sounds very interesting and encouraging. I see you have found the original article, the update is also on slideshare somewhere. I haven’t really thought much about cost, but as you…
  • michaelkellett
    michaelkellett over 5 years ago in reply to shabaz +7
    I can't live with that - I have to have symmetry The problem is that the Howland current pump doesn't constrain the voltage on the load at all when perfectly balanced - and my LTSpice model is unrealistically…
  • michaelkellett
    michaelkellett over 5 years ago in reply to michaelkellett +7
    AS promised - now for the phase sensitive detector. I couldn't easily model this in LTSpice, which is no great surprise because it needs multiplication and square roots. I used Simulink in MATLAB - which…
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  • genebren
    genebren over 5 years ago

    Interesting ideas so far.  I meant to chime in earlier, but things have been pretty busy for me lately (building a deck and entertaining my Grandchildren again).

     

    Several years ago, I was asked to sit in with some friends of my sister that work at a geotech company.  They were looking to build impedance measurement devices for soil surveys.  I came across this amazing looking chip from Analog Devices that looked like a great way to measure impedance (including a complex component).

     

    Here is a snippet from the specification:

     

    The AD5934 is a high precision impedance converter system solution that combines an on-board frequency generator with a 12-bit, 250 kSPS, analog-to-digital converter (ADC). The frequency generator allows an external complex impedance to be excited with a known frequency. The response signal from the impedance is sampled by the on-board ADC and a discrete Fourier transform (DFT) is processed by an on-board DSP engine. The DFT algorithm returns a real (R) and imaginary (I) data-word at each output frequency.Once calibrated, the magnitude of the impedance and relative phase of the impedance at each frequency point along the sweep is easily calculated using the following two equations:Magnitude = 22IR+Phase = tan−1(I/R) A similar device, available from Analog Devices, Inc., is the AD5933, which is a 2.7 V to 5.5 V, 1 MSPS, 12-bit impedance converter, with an internal temperature sensor, available in a  16-lead SSOP.

     

     

    This might be of some help in your planning.

     

    Good luck and let me know if you need any help on this project.

     

     

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  • fmilburn
    fmilburn over 5 years ago in reply to genebren

    That is a pretty neat chip.

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  • fmilburn
    fmilburn over 5 years ago in reply to genebren

    That is a pretty neat chip.

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