I have the Arduino Uno (non-original replica) board, general SPI lcd, and GUVA-S12SD analog UV sensor module. The board (powered via USB) reads the data from the analog pin 0, converts it to voltage (multiplying the readout by (5.0/1023.0) ) and prints out to the LCD.
Being illuminated with an UV-flashlight, the sensor gives unstable readouts varying for around 0.03-0.04 V each readout cycle. I am a complete noob in electronics, so I want to ask how can I check where the problem is? Is this my error in wiring, faulty module, just normal behaviour of an analog sensor or something else?
Mine sensor module isn't from Adafriut and looks a bit different, the one in the diagram is just to show the general wiring.
(Sensor module description: https://www.electroschematics.com/11509/guva-s12sd-uv-sensor-module-circuit/ )
The code of the sketch is:
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
int sensorValue;
float sensorVoltage;
LiquidCrystal_I2C lcd(0x27,16,2); // display setup
void setup() {
lcd.init();
lcd.backlight();
lcd.setCursor(0, 0);
lcd.print("");
}
void loop() {
sensorValue = analogRead(A0);
sensorVoltage = sensorValue * (5.0 / 1023.0);
lcd.setCursor(0, 0);
lcd.print(sensorVoltage/0.1); // rather low voltage is expected
delay(1000);
}
Update: I tried to measure the output with a multimeter (as Vasekdvor suggested in answers) and it showed very similar results: continuous 0.04-0.07 V oscillations. Their magnitude seems to grow along with the intensivity of the illumination.
With sensor being dark, multimeter shows 0.006 V (changing to 0.007 V occasionally) between A0 pin and the ground.