Anemometer only showing up to 36 kph

Projects Programming
1

Hi,

I am puzzled with a problem and would like to ask for some advice on this.
I've got an anemometer FST-200 and this should give a wind speed value from anything from 0 kph all the way up to 180 kph.
I have connected the input to an analog pin A15 on a MEGA2560.
This device works great all the way up to 36 kph. This is the absolute maximum I've ever recorded.

Here's my code:

The variables:

//Anemometer FST200
  int readWindSpeed;              //Read analogue input A15 (0-1023)
  float windSpeed;                //Current wind speed

The function

void windSpeedFunction() {
   readWindSpeed = analogRead(A15); //Read analogue input A11 (0-1023)
   windSpeed = map(readWindSpeed, 0, 5, 0, 180)/1000;
}

So basically I'm monitoring the voltage on A15 (0 to 5 Volts) and then scale it to a value between 0 to 180 kph.
Why does it hang up at a maximum of 36 kph?

Your opinion will be appreciated! Thanks.
Cheers,

Luc

2

Your comment says that readWindSpeed could have a value from 0 to 1023, and then you map 0 to 5 VOLTS when you should map 0 to 1023. Furthermore, the result of the map function is long, so the division by 1000 will be an integer division (e.g. 999/1000 is ZERO!).

Fix those problems and then get back to us... and show the ENTIRE program next time.

3

Problem solved!

The problem was caused by another sensor (Rotronic humidity sensor). The latter needs an analog voltage between 0 and 1V.
So, at the start of the humidity function I had included:

analogReference(INTERNAL1V1);

So, this limits the analog voltage to 1V.
The anemometer hung up at 36 kph, which is exactly the value of 1V (36 kph x 5 = 180 kph).
So at the start of the anemometer function I had to include following line:

analogReference(DEFAULT);

My apologies for wasting anybody else's time.

The code is for my weather station. So far I've got about 800 lines of code. That was the reason why I didn't send the whole sketch.

Cheers,

Luc

4

Uh, NO. There is a good chance that someone, possibly me, could have picked out the real problem if we could have seen ALL of the code.

5

could have picked out the real problem

The problems you did discover are real problems.