First of all, happy new year to all of you, and I wish you all the best for the coming new year!!!
I am setting a Pyranometer from Davis Instrument https://www.meteo-shopping.fr/files/doc/Pyranometre-pour-mesure-du-rayonnement-solaire-Documentation-6450.pdf
My main concern is about the sensor calibration, because it look like it need to be calirated, isn’t?
First here some information about my board.
I am using a ATSAMD21G18 ARM Cortex M0 at 48Mhz with 3V3 logic board with 256K memory.
My analog output résolution is 10
and I connected my AREF pin to 3.3V pin to have a 3.3V analog reference.
The doc say:
Range of measure : 0 to 1800W/m2
Analog output: 0 à 3V CC; 1.67 mV par W/m2
The sensor is powered with a 3.3V digit pin
Analog output is connected to A2 without pull-up or down resistance
GND is connected to GND
I have created the following code
[sup] [/sup] [sup]float sunValue = analogRead(pin_readSun); //Get a value between 0 and 1023 from the analog pin connected to the anemometer Serial.print(F("DEBUG: ")); Serial.println(sunValue); float v1 = (3/1023.0) * sunValue; Serial.print(F("DEBUG: ")); Serial.print(v1); Serial.println(F("V")); float sunValueWm2 = (1796.4 / 3) * v1; Serial.print(F("Sun radiation: ")); Serial.print(sunValueWm2); Serial.println(F("W/m2"));[/sup]
The problem I obeserved, it during the night or when I cover the sensor with a box, the sensor measure 38W/m2 but during the day (bad weather) the sensor measure up to 140W/m2
I am surprised about the 38W/m2 during the night, or when I cover the sensor with an object. It should return 0W/m2 or some thing close to the zero, isn’t?
That’s the reason, I supposed it should be calibrated, but I have no idea how, as I can not produced 1800W/m2, or let say 1796.4 W/M2.
My main question is, someone has a experience with the Davis Pyranometer and could tell me how to calibrate it , or to exlain me why I get 38W/m2?
My other question , as voltage reference of the sensor is 3V, and my analog reference is 3.3V, do you really think it make a big difference?? I do not think, it’s a problem as the sensor will never return more than 3V.
I hope someone has an experience with the Davis Pyranometer and how can I make it working with a 3.3V board?
Many thank and happy new year