Today I started a measurement series by preparing control solutions with different glucose concentration, measuring the concentrations with the commercial glucose meter and comparing the results with the measured transimpedance amp and op amp integrator output voltage of my DIY glucose meter. I used Excel scatter charts to apply linear regression.

Test code:

int current = 0;
int integral = 1;
float threshold = 2.8;

void setup() {
  Serial.begin(9600);
  pinMode(6, OUTPUT);
}

void loop() {
  float current_voltage = analogRead(0) * (5.0 / 1023.0);
  float integral_voltage = analogRead(1) * (5.0 / 1023.0);
  if(current_voltage > threshold) {
    // reset integrator
    digitalWrite(6, HIGH); 
    delay(100);
    digitalWrite(6, LOW);
    //delay 5 seconds like the ONE TOUCH ULTRA 2
    delay(5000);
    current_voltage = analogRead(0) * (5.0 / 1023.0);
    integral_voltage = analogRead(1) * (5.0 / 1023.0);
    Serial.print("Current to voltage: ");
    Serial.println(current_voltage,5);
    Serial.print("Integral to voltage: ");
    Serial.println(integral_voltage,5);
    while(1);
  }
}

Scatter charts:

As we can see the relation between the glucose concentration and the transimpedance amp output voltage is nearly linear. We can obtain following formula for computing the glucose concentration by the transimpedance amp output voltage: