Modern Device: Wind Sensor Rev. P Anemometer
The Rev. P4 wind sensor is the latest revision of our wind sensor. The revisions are mostly tweaks for stability and accuracy. We also added a potentiometer to make calibrating the boards easier. We will calibrate them in the shop and the pot really shouldn’t be a user item, unless users want to experiment with them. We will also be doing a new regression and revising our code to support the sensor in the coming weeks.
The Rev. P wind sensor is an improved hot wire anemometer, similar to our Rev C wind sensor but including hardware compensation for ambient temperatures. The “P” is somewhat arbitrary, but can also stand for positive temperature coefficient thermistors. The thermistors used on this model are more stable and more absolutely accurate than the thermistors on the Rev C. As with everything in engineering, the new thermistors have good and bad effects. Because we can’t buy the thermistors in arbitrary values, it requires a higher voltage to heat the sensing element to operating temperature. Thus the sensor needs an 9-12 volt supply. Another downside is that the parts are dramatically more expensive than our Rev C. sensor.
One pleasant side-effect of the increased voltage is that there is plenty of power to heat up the thermistor, so the sensor can sense hurricane force winds without saturating (going to a flat maximum value). It does not necessarily mean the sensor can survive hurricane force winds however. The new mounting of the thermistor sensing element means that the Rev P is much less directionally sensitive than the Rev C. sensor. Perhaps in the 15% range. The sensor should also be physically more robust than our older sensor due to the loop that holds the sensing element. Another new feature of the sensor is a dedicated ambient temperature sensor that is independent of supply voltages. The temp sensor analog output is also scaled to 3.3 volts. The voltage (wind) output of the sensor has also been scaled to a maximum 3.3V output with high precision (.1% resistors). This is to accommodate the increasing use of 3.3 volt boards, and microcontrollers. It will work great with any Arduino or clone, right out of the box, except for the fact that you need to provide at least 9-12 volts from an external power source, with 12 volts being ideal.