looks like your right , this morning the outside temp is -12c with the sun shining on it.
I was not accurate saying the sensor was covered in ice , it had water and ice on it , so i think wind chill was still at work or am i wrong
Tom is correct, wind will have no effect on a (dry) thermometer. Wind chill is in effect a measurement of how wind will assist in drawing heat from a body which is trying to retain heat. With no wind, (and thus no heat transfer through forced convection), you will remain warmer. With the wind, convective heat transfer is increased, chilling you more quickly.
explains it well enough and has charts (Celsius or centigrade, and Fahrenheit along with wind speeds). So yes 20 degrees with a wind might feel like 10 degrees.
What you have with your *wet* thermometer is in effect what they call a wet bulb thermometer (a thermometer kept wet and subjected to air flow, which is used along with a dry thermometer to determine relative humidity). The wind, even as cold as it is, helps vaporizes some of the water. Heat is required to accomplish the phase change from liquid to vapour, which is drawn from the water and ice, cooling the thermometer below the actual temperature of the air. So again Tom is right, I guess, in saying the thermometer is reading the temperature of the ice.
This is the same as how vapourizing sweat on a dry day, with a nice breeze, will cool you. Sweat on a hot humid day, even with a breeze, does zip or close to it; other than make you feel clammy, and maybe stink a bit more than usual.
In winter, damp weather without wind I think just feels colder because heat conduction (as opposed to convection, above) is aided by the moisture screwing up the insulating value of your clothing, or the usually insulating dry static (unmoving) air near the body.
Riding wet in the the cold just sucks the heat out of you - this many of us know well, damn the science.