Inspeed Wind Speed Sensor Accuracy InformationThe accuracy of any device is a function of the "system", meaning the sensor, the electronics, and the display all together. In this case, we are providing accuracy information relative to Inspeed-manufactured Vortex Series wind speed sensors attached to various bicycle speedometer displays. Ultimately the accuracy is a function of the specific display used; here we use data obtained with a Sigma Sport BC1200 bicycle speedometer. We assume that given the same Wheel Size (WS) input, the accuracy would be the same for any speedometer used.
ACCURACY STATEMENT - With Bicycle Speedometer Displays
Inspeed anemometers (with displays) are guanteed to be accurate to +/- 1 mph or 4% of reading, whichever is greater, in the range of 10mph to 50mph.
That means that at 10 mph the accuracy is +/- 1 mph and at 50 mph it is +/- 2mph.
We find that given the natural variability in actual wind speeds, this accuracy is not only competitive with instruments that cost two to four times as much, it provides all the accuracy necessary for our intended markets.
NOTE that this accuracy requires and assumes that the wheel size (WS) is set according to the instructions provided by Inspeed. See the Help & Support page to find correct WS settings for various speedometers.
Why 10 to 50 mph range? what about lower and higher speeds?
LOW SPEED RANGE (below 10 mph) : we find that the lowest practical, usable speed for the Inspeed anemometers is approximately 5 mph. Below that the pulse rate and friction are not suitable for proper, reliable measurements. If the intended applications require high accuracy in the 1-10 mph range we woud recommend impeller-type sensors (which we do not make or sell!).
MID SPEED RANGE (10 to 50 mph):
Believe it or not, we could not find a wind tunnel capable of verifying our anemometers at speeds higher than 50 mph. We sent our anemometer/BC1200 display to Davis Innotek, where it was verified in their calibrated wind tunnel.
The results are shown in the table below, where the error was approx. 0.7 mph at 10 mph and 1.5 mph at 45.5 mph.
ABOVE 50 mph
We could not find a wind tunnel able to verify our instruments at speeds over 50 mph (please CONTACT US if you know of a source that can), all our accuracy data above 50 mph is implied and anecdotal - based on customer feedback and personal experience. Given the linearity of the output of the rotor, and with reference to our supplier (Cape Cod Wind & Weather), we believe the accuracy of Inspeed anemometers to be 4% of reading up to at least 125 mph - more like 175. We just don't know! This accuracy, however, has not been verified. All we have is customer feedback where the readout has been compared to vehicle speedometers in calm conditions at speeds well over 100 mph. We also have customers with other devices and who compare results.
The maximum speed of the anemometer is not known. We have photos of customers pointing high pressure air at the cups and producing 195 mph output - so we know it can spin that fast...