So we have this experiment that "tries" to measure the response of photodiodes with different colors of light. We had a reverse biased photodiode in series with a resistor. The voltage is measured across the resistor with 10M ohm resistance.
Using a multimeter, there is some noticeable difference in voltage readings. However, using the Arduino, we got this:
0.04
0.00
0.00
0.00
0.00
0.00
0.62
0.63
0.56
0.26
0.46
0.14
0.03
0.13
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.59
0.72
0.64
0.57
0.63
0.52
0.41
0.36
0.37
0.39
0.07
0.03
0.05
0.04
0.00
0.01
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.59
0.65
0.43
0.38
0.31
the program we used is this:
/*
ReadAnalogVoltage
Reads an analog input on pin 0, converts it to voltage, and prints the result to the serial monitor.
Attach the center pin of a potentiometer to pin A0, and the outside pins to +5V and ground.
This example code is in the public domain.
*/
// the setup routine runs once when you press reset:
void setup() {
// initialize serial communication at 9600 bits per second:
Serial.begin(9600);
}
// the loop routine runs over and over again forever:
void loop() {
// read the input on analog pin 0:
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(500);
}
I've read that the input is expected to fluctuate when there the pin is not connected to anything. But I am sure that ours was connected to measure the voltage across the resistor. What could be wrong?