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Author Topic: Metal imaging system  (Read 2694 times)
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OP, I think you're confused about timescales.
One thousand milliseconds is one whole second.
Any effects you're likely to measure will be on the milli or micro second scale.

OK now THAT HELPED.  I increased the length of the "on" position.  I got a reading finally.  The readings are happening at the same rate as the on/off switch, so it's either sampling right as it turns off, or right as it turns on.  I have to figure out how to sample on the shut-off, or just do continuous sampling and see if it changes when I add remove conductive objects.
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I think you will need some pretty fancy analog processing before you even get to the arduino input, this is one of the reasons I gave up on the Proton magnetometer,  trying to dig the fading signal out of the noise after energising the target.


Sounds about right.  That's why I wanted to tackle analog processing first.  I know metal detectors, resistivity testing, and induced polarization works.  What I don't know is how to put them in an array and make the readings relevant. 
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OP, I think you're confused about timescales.
One thousand milliseconds is one whole second.
Any effects you're likely to measure will be on the milli or micro second scale.

OK now THAT HELPED.  I increased the length of the "on" position.  I got a reading finally.  The readings are happening at the same rate as the on/off switch, so it's either sampling right as it turns off, or right as it turns on.  I have to figure out how to sample on the shut-off, or just do continuous sampling and see if it changes when I add remove conductive objects.

How can I program an increase in the sampling rate?
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I think I figured it out...I turned the power on continuously and started sampling at 1 sec intervals.

Code:
/*
  Blink
  Turns on an LED on for one second, then off for one second, repeatedly.
 
  This example code is in the public domain.
 */
 
// Pin 13 has an LED connected on most Arduino boards.
// give it a name:
int led = 13;

// the setup routine runs once when you press reset:
void setup() {               
  // initialize the digital pin as an output.
  pinMode(led, OUTPUT);
  Serial.begin(9600); 
}

// the loop routine runs over and over again forever:
void loop() {
  digitalWrite(led, HIGH);   // turn the LED on (HIGH is the voltage level)
  int sensorValue = analogRead(A0);
  // Convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V):
  float voltage = sensorValue * (5.0 / 1023.0);
  // print out the value you read:
  Serial.println(voltage);
  delay(1000);               // wait for a second
}

/*
 
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That link is fine, how you are interpreting it is rubbish.
Terms like residiual voltage traces are pure rubbish as is the way you are testing it.
It dosn't work you said, that is not news, what would be news is if you got some sort of effect from that test. You are totally missunderstanding how geophysical measurements work.
These sorts of effects are observable in bulk ground measurements, not with a lump of metal in a cup.

I'm getting some dirt for my cup.  And I'm adding salt water.  The ultimate goal is to make this a marine survey tool, adding to the resolution of the systems here: http://www.heritagegeophysics.com/resistivity/resistivity_imaging.htm#marine
http://pubs.usgs.gov/misc/ipstreamer/IP-Streamer_Wynn-Giller.pdf
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I don't have an exact chip to suggest but basically any ADC that works with spi (serial protocol interface I think ), basically each adc shares 3 wires(databus) and one has its own chip select, this would be the fastest way
you could also get an adc that uses i2c instead and you will have only a 2 wire then, but its alot slower
the point tho of using a databus tho would be instead of 100 sensors all connected in one spot you could split it up in groups with alot less wires at the mcu
The only time I've seen something with that many analog inputs was a mixing table from 1986 it didn't have that many but it had 4 8channel adc that communicated thru an 8bit data bus with a separate adress bus, lol but that's oldschool I guess
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