Wind measurment with Twido

What is the best way to take a anemometer pulse signal and count it and figure out the MPH. The sensor puts out 2.5 pulses per MPH. I am not familiar with Twido counters...so any help would be appreciated.... I will be sending this data to a magelis and also using for some internal calculations.

Hi,

From memory, the first 4 inputs of a Twido (at least the model I saw) could be used to drive a high speed counter instruction.

From that instruction, you should be able to do some maths using %MW words (say multiply by 25, then divide by 10) to do your conversion.

Do you have any way of testing your system (ie have you purchased the hardware?)


I saw an application where an encoder was connected to the first or second digital input, which was used to give machine position (in degrees, after some maths was done). I can dig this out if need be...

Do you mean when the anemometer is pulsing at 1/2.5 = 0.4Hz = 1mph?

I do something similar with a counter input on a Micrologix. I read the count every 25 seconds (set exactly with an interrupt) and use the result to get mph.

For M pulses in 25 seconds
N frequency = M / 25

mph = 2.5 x N = 2.5 x M / 25 = M / 10

For m/s

m/s = 0.44704 x 2.5 x N = 1.1176 x M / 25 = 0.044704 x M
(1 mph = 5280 feet x 3.048 / 3600 m/s = 0.44704 m/s)

I normally read the calculated result every minute and average it over a period of time - works out quite well as a random sample.

Al

PS Use lightning protection on your anemometer input!

If your also going to be including wind direction you might find this thread has some useful hints and pitfalls with measuring wind direction and setting an average