wind sensor sudden drastic changes in output values

[ladykbrooklyn]

Hello,

I'm using a Wind Sensor Rev C and it's been working nicely. I'm using it with an Arduino Uno and a TFT Screen from Adafruit. I have it on a regulated supply (9volts) via a 7805 voltage regulator.

Here is my code:

Code: Select all

const float zeroWindAdjustment =  .2; // negative numbers yield smaller wind speeds and vice versa. // was.2

int TMP_Therm_ADunits;  //temp termistor value from wind sensor
float RV_Wind_ADunits;    //RV output from wind sensor
float RV_Wind_Volts;
unsigned long lastMillis;
int TempCtimes100;
float zeroWind_ADunits;
float zeroWind_volts;
float WindSpeed_MPH;
float Wind_speed;
float wind;

//........

float checkWind() {
  TMP_Therm_ADunits = analogRead(analogPinForTMP);
  RV_Wind_ADunits = analogRead(analogPinForRV);
  RV_Wind_Volts = (RV_Wind_ADunits *  0.0048828125);
  TempCtimes100 = (0.005 * ((float)TMP_Therm_ADunits * (float)TMP_Therm_ADunits)) - (16.862 * (float)TMP_Therm_ADunits) + 9075.4;
  zeroWind_ADunits = -0.0006 * ((float)TMP_Therm_ADunits * (float)TMP_Therm_ADunits) + 1.0727 * (float)TMP_Therm_ADunits + 47.172; //  13.0C  553  482.39
  zeroWind_volts = (zeroWind_ADunits * 0.0048828125) - zeroWindAdjustment;
  WindSpeed_MPH =  pow(((RV_Wind_Volts - zeroWind_volts) / .2300) , 2.7265);
  WindSpeed_MPH = WindSpeed_MPH * 100.0;
  return WindSpeed_MPH;


}

The values I am now getting from the sensor, are markedly larger than what I had the night before. Last night I was getting values around 0.8. This evening it's about 200 when it's cool. The environment has not changed. I did unplug the sensor's wires from the Arduino and unplug the power supply from the wall. The sensor is attached to a stable environment. The code is the same. The delicacy in response from the wind sensor is no where near as defined as it was before. Not only that, but it seems to need significant cooling-breaks, otherwise the wind speed never comes back down.

This is also the second time this has happened to me with a different sensor (but still a Rev C).

I'm wondering what can cause this, especially so I can build a stable project.

Also, if you have a tip for a tip of tool to calibrate the sensor, please let me know. I have a bazillion small screw drivers for a myriad of screw types. None of mine seem to fit the pot correctly.

Thanks in advance for your time,

ladyk

[oz]

ladyk,

Are you using the sensor in an enclosed space by any chance?
Also is the sensor seeing only very small wind velocities?

I'm thinking that there may be some thermal buildup going on somewhere.

For the sketch to work in a calibrated fashion, it's important to use the RV (raw output) and not use the output affected by the pot.

Paul