Thermo-hygrometers and simple weather stations

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What is a thermo-hygrometer

A thermo-hygrometer is a dual measurement device that shows, commonly on a LCD, current values for relative humidity and temperature in the area nearby the product.

Thermo-hygrometers have been available for many decades but consumer devices with reasonable accuracy and a compact size are present on the market for less than 15 years. Previous digital devices have been relatively expensive while analog devices were bulky and could not operate in certain environments, such as outside.

For most intents and purposes, thermo-hygrometers and very simple weather monitoring stations have the same capability and features. Slightly advanced devices have wind and precipitation monitors that are not useful for energy consumption and comfort evaluation, they have special purposes outside of the current scope.

A simple weather station benefits

Compared with traditional thermometers or hygrometers, a thermo-hygrometer combines both all-important data gathering in a single device. This matters as even small differences in the location of sensors or time of measurement could make assessment about indoor or outdoor conditions much less reliable.

A simple weather station combines the features of a stand-alone thermo-hygrometer as well as a remote sensor with similar capabilities. Bundling two such devices is convenient, cost-effective and brings much more flexibility for monitoring, being the recommended approach.

Good weather stations

While there are many brands and models, a good product should have the following capability:

  • slim, versatile design, can be hanged, wall-mounted or placed on its stand
  • battery operated, so that it can be placed just about anywhere
  • ideally use AA instead of AAA batteries for longer operation time
  • reflective LCD display (greyish-green when off) for good readout in low light
  • digital readout for relative humidity (%) and temperature (Celsius/Fahrenheit degrees)
  • show temperature and humidity trends (with an arrow)
  • ideally support additional sensor to monitor another indoor/outdoor area
  • the remote temperature/humidity sensor is wireless and battery-operated
  • the main unit has clock display, to simplify data tracking

Simple Weather Station

The above pictured thermo-hygrometer is actually a simple weather station that has all of the above capabilities as well as a barometer and trend indication for atmospheric pressure. The barometer is not important for most use scenarios but can be a welcome free addition.

Why temperature and relative humidity matter

While temperature is obviously one of our most important information about the environment, humidity is just as important, even if slightly less understood. Our perception of an unbearable chill or hotness is closely linked to humidity.

For instance, our cold perception is amplified when experiencing damp environments such as mist or fog, while a hot perception becomes unbearable when humidity is high since our body temperature cannot be lowered by perspiration and evaporation.

Indoor Temperature Relative Humidity Comments
20-29 (Celsius degrees) 35 slightly dry, may be uncomfortable for some people
20-29 (Celsius degrees) 40-60 common comfort zone
20-29 (Celsius degrees) >60 high risk of mold growth, risk of goods damage
20-29 (Celsius degrees) >70 serious issues for health and goods

Every person has a different comfort zone or array of temperature/humidity values where he or she can comfortably live and a fringe area where comfort starts to drop as values diverge from the ideal condition.

Some people prefer slightly cooler environments but with low humidity while others may enjoy bot hot and humid places. There is little that can be done to change personal preferences even if they adjust somewhat during life.

Indoor/Outdoor monitoring devices

The device can be standalone or part of an array of measurement devices. In case it is part of a distributed measurement system, a larger area can be covered and monitored for indoor comfort. Some thermo-hygrometers can have a separate sensor that can transmit wirelessly data to the main unit, giving the important capability of monitoring outdoor climate conditions of humidity and temperature.

Setting up a thermo-hygrometer is straightforward. Units that have a remote sensor have to be placed considering the reliable operating range, usually less than 10 meters in buildings, and have a pairing procedure.

Exterior Sensor Mounting

Outdoor placed sensors have to be protected with a top cover so that water does not enter the unit but can be drained easily if it condenses inside. The units should be placed at a small distance from exterior walls and sun to avoid wrong measurements.

Indoor placed sensors should be far from direct water spills, placed at a height of around 1 to 2 meters, to ensure relatively easy access yet provide enough useful data. Rooms with particularly challenging humidity and temperature swings, such as bathrooms and kitchens should be particularly monitored. In large working areas, the sensor should be placed close to the center.

During winter and summer, another good spot for measurements is near windows as condensation and chill is present in winter and intense heat from the sun is present in the summer, giving early information about large comfort issues.