What is the best way to mount a weather station and an anemometer? All sensors have their limitations and require proper placement for accurate results.
“Measure accurately or don’t measure at all” from the words of our founder Mr. Barani. “Bad measurements give misleading results and lead to wrong conclusions.”
If you follow these simple rules, your weather station data will be as reliable as a professional’s. Since most of us are limited in sensor placement by where we live, here are a few simple rules to follow for weather station placement, along with their explanations.
SIMPLE AND QUICK WEATHER STATION PLACEMENT GUIDE
(Practical rules for weather station placement)
|Instrument / Sensor / Atmospheric Property||Placement and mounting recommendations||Why? (the reasons behind each sensor placement rule)|
|Anemometer (wind speed sensor) Wind Vane (wind direction sensor)||Place anemometers at least 2x the height of any large hard object within a 50 meter (50 yard) radius.||Wind cannot flow through hard objects like houses, so it is heavily distorted by them as it must flow around them and creates a wind shadow of bad turbulent air flow behind them. If you mount an anemometer too close to a hard obstacle, you will be measuring turbulence and not wind speed and wind direction and your measurements will be very chaotic and inconsistent, and for the large part useless, unless turbulence measurement was your intended purpose.|
|Place anemometers at least 3 heights away from the closest tree. Dense trees require more distance, just like hard objects in the previous point.||Wind can flow through trees, but they slow it down. Trees cause wind shadows, though not as strong as houses do. Many times, trees are tall and placing weather stations above them is not practical. It is important to give wind enough distance to speed up to its regular speed after it encounters a tree. Ideally, an anemometer or weather station will be placed at minimum 2X higher than nearby vegetation.|
|Place a lightning rod same distance away as above the anemometer. No closer than 2m (6ft) horizontal distance and 2m (6ft) above the anemometer.||As a rule, a lightning rod will protect your sensors from direct lightning strikes if the sensors are placed within a 45 degree cone under it. If you place a sensor 7ft from the lighting rod, then make sure it is also 7ft or more below it.
Just the energy radiated from lightning can damage sensors many feet away. It is important to keep all electronics a minimum distance from possible lightning impact points. A lightning rod can protect your sensor from a direct hit, but the energy radiating from lightning may still render the sensor’s electronics useless.
Lightning is unpredictable and dangerous. Always protect yourself and your equipment!
|Humidity and Dew Point sensors||Place dew point & humidity sensors as far away from trees and ponds as possible and no less than 2m (6ft) above ground.||Vegetation expels moisture, thus any moisture sensors like humidity and dew point sensors in its vicinity will measure higher readings than normal. Place your hand near a good humidity sensor and you will see its humidity reading immediately rise. Ponds, moist soil, wet pavement or a house after a rain storm, trees, grass and all living things increase humidity around them. Thus it is important to place humidity and dew point sensors in well ventilated or windy places.|
|Air Temperature sensors||Good temperature sensors require radiation shields (white plates stacked on top of eachother) and to be placed no less than 2m (6ft) above ground and away from any walls, pavement, trees and vegetation.||All objects heat up in the sun. 99% of them become hotter than the ambient air around them…like your car on a sunny day. Air very close to hot objects tends to heat up, thus placing a temperature sensor near objects in direct sunlight will show artificially high temperature. Since relative humidity values are very sensitive to air temperature, humidity readings will be artificially low.
Hot objects also radiate heat. Few inches (cm) above your car’s trunk you will not only feel warmer air but also heat radiating from the object. Same is true of walls, trees, ground and all other objects warmed up by the sun. Shielding your temperature sensor from the sun and heat radiation from objects heated by the sun is very important.
|Rain Gauge (Precipitation sensor)||Industry standard placement is 1m (3ft) above ground and away from objects that effect wind which may shade it from rainfall on windy days.||Most accurate precipitation measurement is on the ground where wind speed is always zero. But since critters can easily crawl into rain gauges placed on the ground and animals can use them as watering holes, a 1m (3ft) height is a good compromise. At this height however, wind can blow quite fast and introduce error into our measurements, thus a good design is important.|
|Barometric Air Pressure Sensor||Wind speed will effect air pressure measurements so placement in a windless place is important unless the sensor is built into an anemometer with built in wind speed compensation like our weather station products.||As air speeds up, its static (barometric) pressure is converted into a dynamic pressure force which we feel on our bodies when standing in the wind. This pressure force lifts airplanes and causes damage during hurricanes. As wind slows down, energy in the wind is returned back into static pressure which is what meteorological pressure sensors reads and what causes our ears to pop when we drive through a tunnel or go up a mountain. Thus, it is important to compensate atmospheric pressure sensors for wind speed or place them in areas shaded from wind (wind shadows).|
|Lightning Sensor (Lightning Proximity Sensor)||Electrical and magnetic radiation from lightning can travel long distances, so placement of lightning sensors is not so critical in this sense. We however, strongly recommend placing them away from strong electrical sources, industrial machines, fans and wall outlets to minimize noise and false signals.||Lightning radiates its energy in many forms. Its light can be seen and its heat can be heard in the form of thunder caused by super heated ionized air suddenly expanding into a thunder clap like from a fire cracker. What we can’t see are ultraviolet, infrared, electrical and radio waves that lightning emits. Electrical and radio waves are the signals that lightning sensors record. Electrical and magnetic waves from a close lightning strike can damage lightning sensors and all household electronics. These waves travel almost at the speed of light and some can travel through objects to reach our lightning sensors.
Industrial equipment, fans and other sparking equipment can however fool or give false lightning strike signal data and placement of lightning sensors near these interference sources is not recommended.