Re: [DIYbio] Conductivity measurements with Bipolar Pulse

On 19-11-2015 17:35, John Griessen wrote:
> On 11/19/2015 01:04 AM, Nathan McCorkle wrote:
>> I considered that you might not be
>> sampling on both pulses, like if one was a 'reset' pulse... but if you
>> don't mean to do that, then I think you need another sense resistor
>> and use another of the analog inputs.
>
> Yes, you probably want to flip the whole experimental setup around
> and attach everything that was on one electrode to the other and vice
> versa.
>
> So, if you cannot see how to do that via using different pins of the
> microcontroller,
> you could add an analog switch IC to act like a patch panel.
>
> Or, get big or small medieval style DC relays chunking or clicking to
> do the swap around.
>

Hi John,

I'm doing by this way:

const float V_arduino = 5.00;

byte pin_electrode_1 = 7;
byte pin_electrode_2 = 8;

int reading_pin = A0;
int reading;

float Vm;
float Rc = 10000; //Constant resistor
float Rx; //Resistance of solution

void setup()
{
Serial.begin(115200);
pinMode(pin_electrode_1, OUTPUT);
pinMode(pin_electrode_2, OUTPUT);
}

void loop()
{


//Pin 7 = 0V e Pin 8 = 5V
digitalWrite(pin_electrode_1, LOW);
digitalWrite(pin_electrode_2, HIGH);

delayMicroseconds(2000);

//Pin 7 = 5V e Pin 8 = 0V
digitalWrite(pin_electrode_1, HIGH);
digitalWrite(pin_electrode_2, LOW);

delayMicroseconds(1900);
reading = analogRead(reading_pin);

digitalWrite(pin_electrode_1, LOW);
digitalWrite(pin_electrode_2, LOW);

Vm = reading * 0.0048;
Rx = Rc * (V_arduino - Vm) / Vm;

Serial.print(Vm);
Serial.print(" ");
Serial.println(Rx);

delay(500);

}

Any tip?

Many thanks,
Markos

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