this inscrutable show how to make an wind speed meter. it's really easy so its won't need more than 5 minutes to make it .
Step 1: Materials
for this inscrutable you will need :
-230v cable (without grounding)
Step 2: Changes on the Multimeter
pull out the cables from the multimeter and insert the brown one to the "COM" and the blue one to the "V ohm mA".
at the other end of the cable the computer fan's red wire to the blue one and the black one to the brown.
Step 3: Calibration
ask someone to help whit the calibrating.
put the fan on your bike and start riding whit 10 km/h the other people (in my case my sister ) hold the multimeter.
when you reach the 10km/h ask he/she what is the multimeter shows. here is my result:
but its deepens on the fan so check it!
Step 4: Placing
when you calibrate it put it into the window like on the picture . when the wind is blowing the fan will rotates and produce electricity that show on the multimeter. you can replace the multimeter whit an led or anything the choose is yours.