Tag Archives: humidity sensor

CO2, Humidity, Process, Sensors, Temperature

Energy Efficiency and Indoor Air Quality

1 Comment

Some of the key factors for improving energy efficiency in relation to indoor applications are the control of Relative Humidity (RH) and temperature. The question is, how to control RH to acceptable levels in an energy efficient manner. Energy efficient humidity control has a very strong bearing on thermal comfort, Indoor Air Quality (IAQ) and eventually on the health and performance of occupants in air-conditioned buildings.

slider-pane1-new

Passivhaus buildings are built to a voluntary standard to improve energy efficiency and reduce ecological footprint.

IAQ control seeks to reduce Volatile Organic Compounds (VOCs), and other air impurities such as microbial contaminants. As such it is important to control relative humidity which can be a key factor leading to mould growth and the presence of bacteria and viruses, dust mites and other such organisms.

Buildings rely on a properly designed ventilation system to provide an adequate supply of cleaner air from outdoors or filtered and recirculated air

TrueDry_DR120_HR

Buildings may rely on dehumidifiers like the one above to reduce RH levels to a comfortable range

Air-conditioning systems typically employ a high level of air recirculation to save energy during cooling and dehumidification. Typically recirculation rates are around 80-90%, but can sometimes be even higher. The challenge is not so much in dehumidification, but in doing so without having to overcool. As such, ventilation is integrated for general comfort and economical saving.

Rooms are often designed with specific conditions in mind including temperature, humidity, brightness, noise, and air flow. Careful engineering and implementation of building automation and control is the only way to ensure energy efficiency and building operation conditions are met during occupancy, at the lowest possible costs.

IAQ Facts:

Energy Efficiency (EE) refers to either the reduction of energy inputs for a given service or the enhancement of a service for a given amount of energy inputs.

Relative humidity is highly temperature dependent, so if the temperature is stable, it is much easier to achieve a stable RH.

Air in our atmosphere is a mixture of gases with very large distances between molecules. Therefore, air can accommodate a large quantity of water vapor. The warmer the air, the more water vapor can be accommodated.

Why the need to measure, temperature and relative humidity?

Precise temperature control of air which is supplied to a room results in maximum comfort for the occupants. The temperature should be held constantly at a particular set point to achieve this comfort.

Readings from temperature transmitters installed in the air supply duct are compared to readings inside a particular room. It is easiest to achieve a constant room temperature if there is little difference between the two values. Air temperature control in supply ducts can be employed in rooms in which the air handling unit is used mainly for the renewal of air.

hf3_2_o_display_1

Rotronic manufactures temperature and humidity transmitters such as the one above which are suitable for use in spaces where appearance is a factor.

It is with good RH control that we can process the air for air conditioned rooms independent of the state of outside air and the processes taking place in the room. This way the RH remains constant or within the preset limits and thus energy consumption for humidification and dehumidification is minimized.

Air conditioning is supposed to maintain room temperature and RH as precisely as possible through the use of systems which monitor and control temperature and humidity in the room (or in the air supply ducts to the room). Systems must be dynamic to manage the changing room air quality depending on the occupants and usage.

With precise measurement and control of temperature and humidity, energy consumption for humidification & dehumidification as well as heating and cooling can be reduced leading to energy efficient building operation with lower energy costs and healthier occupants.

Phil Robinson
Rotronic UK

Sensors

Monitoring Transportation

1 Comment

Rotronic has recently released a cold chain logger which can be used to ensure items are kept at the correct temperature during transportation.

tl-cc1_0094Rotronic cold chain logger

Transportation in general

One key aspect of today´s wealth in the modern world is specialization. So towns, regions or even whole countries focus on a few things they are really good at. This can be based on various factors; for example resources offered by the land, climatic conditions or specific knowledge that has been developed over a long period and has been passed on from generation to generation. As an example, Cuba provides brilliant conditions for the Corojo and Cirollo plants, better known as tobacco. Although smoking is quite popular among Cubans, their production of tobacco exceeds the local demand by far. On the other hand they lack other resources and goods. At that point trading, and therefore the importance of transportation, comes into play. In the case of the tobacco the transportation is not a simple task, since it requires a constant high humidity level to maintain the high quality expected from a Cuban cigar.

Tobacco-Fields-in-VinalesTobacco plants in Cuba

Like tobacco there are many products where special requirements for shipping have to be put in to consideration, in order to maintain freshness, internal integrity, colour quality or whatever other properties that could be affected by an inappropriate transportation.

Facts & figures:

A major step in the transportation industry was the international standardisation of shipping containers in 1955. This means that one container can be put directly from a vessel to a truck and transported all around the globe.

Today 28´000´000 ISO containers (20 feet) are permanently on the move, transporting goods from point to point keeping our economy running.

Every year 10´000 shipping containers fall over board.

0.16 Euro cents is the cost of transporting a bottle of Chilean whine to Europe.

Why the need to monitor transportation?

Various factors can have a negative impact on a product during transportation. Below are the most common parameters to be monitored to ensure product quality:

Temperature

Controlling temperature is the key in transporting fresh foods, where the rate of decomposition is reduced significantly by maintaining lower temperatures. It is also important as proof of an uninterrupted cool chain for frozen products or to ensure the effectiveness of medication.

truck_insidesthe back of a temperature controlled lorry.

Humidity

Monitoring humidity ensures that the growth of micro organisms in food and medications remains below critical levels. Controlling humidity also helps to maintain structural integrity of paper and cardboard or to avoid corrosion of metals during a long transatlantic journey in a shipping container.

Pressure

Apart of being able to reconstruct when and how long a parcel`s flight was, pressure is also en essential parameter for products that have to be transported in a vacuum or pressured chamber. This method could for example be used when transporting biological samples or hazardous chemicals.

Shock

To guarantee that expensive machinery, glass, works of art and other delicate products weren’t damaged during transportation, monitoring of the G-force in all three axis is the solution.

Rotronic-HygroLog-Log-HC2-P1-Universal-Humidity-and-Temperature-Data-Logger-Humidity-and-Temperature-Measurement---Large-21391770915

 

The Rotronic LOG-HC2 can log light, temperature, humidity, pressure, and shock.

Light

Light is a good parameter to determine if or at what time a container or package was opened. Also to ensure protection of light sensitive products such as vegetable oils, chemical substances or photo paper.

Philip Robinson                                                                                                       Rotronic UK

Meteorology, Sensors

Wind Turbines

2 Comments

Its been pretty windy recently, So wind farms are probably doing quite well at the moment. The biggest wind farm in the world, at the moment, is the London array, which can produce 630MW of power.

Wind Energy in General

The future is very encouraging for wind power. The technology is growing exponentially due to the current power crisis and the ongoing discussions about nuclear power plants. Wind turbines are becoming more efficient and are able to produce increased electricity capacity given the same factors.

Facts & figures:

There is over 200 GW (Giga Watts) of installed wind energy capacity in the world.

The Global Wind Energy Council (GWEC) has forecasted a global capacity of 2,300 GW by 2030. This will cover up to 22% of the global power consumption.

WindPower
Converting wind power into electrical power:

A wind turbine converts the kinetic energy of wind into rotational mechanical energy. This energy is directly converted, by a generator, into electrical energy. Large wind turbines typically have a generator installed on top of the tower. Commonly, there is also a gear box to adapt the speed. Various sensors for wind speed, humidity and temperature measurement are placed inside and outside to monitor the climate. A controller unit analyses the data and adjusts the yaw and pitch drives to the correct positions.

The formula for wind power density: 

W = d x A^2 x V^3 x C  

d: defines the density of the air. Typically it’s 1.225 Kg/m3. This is a value which can vary depending on air pressure, temperature and humidity.

A^2: defines the diameter of the turbine blades. This value is quite effective with its squared relationship. The larger a wind turbine is the more energy can be harnessed.

V^3: defines the velocity of the wind. The wind speed is the most effective value with its cubed relationship. In reality, the wind is never the same speed and a wind turbine is only efficient at certain wind speeds. Usually 10 mph (16 km/h) or greater is most effective. At high wind speed the wind turbine can break. The efficiency is therefore held to a constant of around 10 mph.

C: defines the constant which is normally 0.5 for metric values. This is actually a combination of two or more constants depending on the specific variables and the system of units that is used.

nordex-wind-turbine-450-x-299

Why the need to measure the local climate?

To forecast the power of the wind over a few hours or days is not an easy task.

Wind farms can extend over miles of land or offshore areas where the climate and the wind speed can vary substantially,
especially in hilly areas. Positioning towers only slightly to the left or right can make a significant difference because the wind velocity can be increased due to the topography. Therefore, wind mapping has to be performed in order to determine if a location is correct for the wind farm. Such wind maps are usually done with Doppler radars which are equipped with stationary temperature and humidity sensors. These sensors improve the overall accuracy.

Once wind mapping has been carried out over different seasons, wind turbine positions can be determined. Each turbine will be equipped with sensors for wind direction, speed, temperature and humidity. All of these parameters, the turbine characteristics plus the weather forecast, can be used to make a prediction of the power of the turbine using complex mathematics.

wind-turbine-controlThere is a small weather station on the top of this wind turbine

The final power value will be calculated in “watts” which will be supplied into power grids. Electricity for many houses or factories can be powered by this green energy.

Why the need to measure inside a wind turbine?

Wind farms are normally installed in areas with harsh environments where strong winds are common. Salty air, high humidity and condensation are daily issues for wind turbines.

Normal ventilation is not sufficient to ensure continuous operation. The inside climate has to be monitored and dehumidified by desiccant to protect the electrical components against short circuits and the machinery against corrosion.

Internal measurements are required to ensure continuous operation and reduce maintenance costs of a wind farm.

Philip Robinson                                                                                                       Rotronic UK

Humidity, Sensors

Timber Drying

1 Comment

We recently visited a company which is involved in the drying of wood, and learned a bit about wood drying. This company had bought a temperature and humidity logger for monitoring their drying environment.

Timber Drying in General

Wood is probably one of the oldest building materials on the planet. But before wood can be used as a construction material, whether it for structural support in a building or to manufacture furniture, it has to undergo treatment to gain the required properties defined by the application in which the wood is used. The first and most important treatment is the drying process.

MINOLTA DIGITAL CAMERAA timber frame for a barn.

The fastest and most effective way to drying timber is in a Kiln. Kiln drying is done in a closed chamber in which air temperature, relative humidity and airflow can be controlled to dry timber to a specified moisture content. The temperature for the drying is usually between 40-90°C depending on type, size and the intended use of the timber. There are many different types of kilns such as vacuum systems, traditional heat and vent type kilns and radio frequency dryers. The cost of installing and maintaining a kiln may often be prohibitive unless a large amount of timber can be processed. However, if the value of specific species is high enough, it becomes more feasible to kiln dry green timber.

Drying_process2Wood in a drying kiln.

Some other drying options timber include: Solar drying where the green timber gets put into a glass house. This option is more often used for drying small amounts of timber. For bigger amounts the Air drying option tends to be used more often. Both drying options are only controllable to a very limited extend since they strongly depend on weather conditions.

Facts & figures:

One cubic metre of freshly felled oak contains approximately 540 litres of water.

Examples for air drying times:

Softwoods: 25mm thick Scots pine that is stacked in April can reach 20 % moisture content by July to August if the summer months are warm and dry.

Hardwoods: 25mm thick English oak if piled in early autumn can reach 20 % moisture content in about 10 months.

A 75mm thick log of wood can even take 3 years to reach equilibrium moisture content.

Why the need to measure humidity?

Controlling humidity during the timber drying process is essential for many factors. An incorrect level of % Equilibrium Relative humidity (ERH) in wood can have the following effects on product and process:

OLYMPUS DIGITAL CAMERAWhen damp, wood is easily damaged.

Dimensional changes

A controlled drying process prevents the timber from unacceptable shrinkage after the installation. But since wood is a natural hygroscopic product it will always change its size to a minor extend.

Strength

Drying the timber below a water contents of 25 % to 30 % will maximise the mechanical strength. dry wood is nearly twice as strong and twice as stiff as green wood.

stess_moisture_plotAs moisture content of wood decreases, the strength increases.

Decay

After drying, timber maintaining less than 20 % moisture content is unlikely to be attacked by wood decaying fungus.

Preservation

To increase the effectiveness of preservative treatments. Many preservatives should only be applied when the humidity of the timber has been reduced.

Corrosion

Drying timber prevents the corrosion of metal fixings such as  nails and screws.

rusty-fixingsWhen wood is wet, it may corrode metal fittings.

Weight

Dry wood is much lighter in weight than wet wood. For many species, dry wood is nearly half the weight of wet wood.

Philip Robinson                                                                                                           Rotronic Uk

Humidity

Humidity and Seed Storage

Leave a comment

I recently visited a facility where they were doing a lot of research into plant biology. As such, it was important for them to have their seeds stored at exactly the correct temperature and humidity to prevent germination or degradation of the seeds.

Seed storage in general

Around 10000 years ago when the first human beings stopped hunting and gathering wild plants, and started to cultivate on farms, preserving and storing seeds became important.

There are various reasons to store seeds, for example, simply preserving grain for consumption later in the year or for sowing during the following season. A little more complex is the collection and preservation of seeds for a longer period of time. This may be done to protect species from extinction or to ensure genetic variety for future generations. Long term storage is also necessary as a back up in case of catastrophic events, such as natural disasters, and disease outbreaks. This type of long term storage is usually done in well protected storage building called seed banks.

Seed-Diversity-in-the-Mil-007A range of seeds in storage

Inside each seed is a living plant embryo which, even in a state of dormancy, breathes through the exchange of gases across its membrane, and is constantly undergoing metabolic processes, also known as aging. The natural lifespan of a seed is influenced by several factors including: permeability of the seed coat, dormancy, and seed physiology. But one of the most important factors is the external environment the seed is exposed to. Temperature and humidity play a key role in the storage capabilities of seeds.

Facts & figures:

The oldest seed that has grown into a viable plant was a Judean date palm seed about 2,000 years old.

The Millennium Seed Bank Project in the UK is the biggest seed bank in the world. Currently they store 31880 species and 1`907`136`030 seeds.

China, with 197 million metric tons, is the world`s biggest producer of rice.

 

Why the need to measure humidity?

Controlling the environment in seed storage is essential for maintaining the germination capacity of seeds, or simply the quality of the seed as a food.

iregi_siteSunflower seeds

In General

Every 1% decrease in the moister content will double the storage life. The same applies for every 5°C decrease of the storage temperature.

A rule of thumb: the sum of the temperature in degrees F and the % relative humidity should be less then 100 for good seed storage conditions.

Storage conditions

Proper storage conditions maintain relative humidity levels
between 20% and 40%, giving corresponding seed moisture contents between 5% – 8%, depending on the type of seed. This range is safe for most seeds. When seed moisture content drops too low (<5%), storage life and seed vigor may decline. When seed moisture content goes above 8%, aging or seed deterioration can increase. Deterioration effects the integrity of the cell membrane, along with several biochemical processes, which overall results in loss of vigor and viability. Seed moisture contents above 12% will promote growth of fungi and insects. Most seeds cannot germinate until seed moisture contents go above 25%.

seedgrowthA newly germinated seed

Seed preparation for long term storage (Seed bank)

To prepare for long term storage, seeds are first put in to a drying room where temperature and humidity is carefully kept at 15°C and 15% relative humidity. Under these conditions the seeds gradually dry out. They are then cleaned, counted and put into airtight containers, before being placed in a seed bank at -20°C. The seeds are then tested for viability on a regular basis.

Philip Robinson                                                                                                                        Rotronic UK

Humidity, Meteorology, Sensors

Meteorology: Numerical Weather Prediction

Leave a comment
The Calculation of Weather Data

What is the weather going to be like tomorrow?

For a long time, people have tried to predict weather conditions using the hydrologic climate cycle.

In the early 1920`s scientists were able to compile a six-hour forecast. Back then it took six weeks to calculate by hand the weather data collected at two points in Europe and create a useful illustrative model.

Today, supercomputers are used to predict the weather for a period of several weeks. The complex modelling programs require several million data points for parameters such as temperature, humidity, pressure, vertical & horizontal wind velocity with time stamps and absolute coordinates. To create a correlation between the data and the environment, scientists “slice” the atmosphere virtually into smaller horizontal & vertical parts – this process is called discretization. It is more useful to compute the chronological change of the parameters using this model.

Meteorological events that are too “small” such as a single thunderhead, layer clouds or smaller turbulences will be parameterised through variables. This parameterisation is a science of its own that aims to reduce uncertainties as best as possible.

754334main_GOES-7Jun2013-0831EDT
Every forecast calculation starts with the current weather conditions. The quality of this input is crucial for the accuracy of the final forecast. Meteorologists link the forecast of yesterday’s weather with the actual measured parameters. Only large data centres are capable of computing this data assimilation. The overall result is a best possible calculation basis to predict the weather for the next day. If this groundwork is flawed the forecast may be incorrect, for example it could report rain at the wrong location.

Today’s meteorological mathematicians also take parameters into account that change extremely slowly compared to the other factors. Growth and the reduction of polar ice, or the temperature of the oceans are summarised as boundary values

After a model is run using all the available data, meteorologists’ process and customize reports for a wide range of target groups such as public authorities, flight control centres, energy producers, industries and many more, including the issue of specific warnings.

Facts & figures:

17.8 cm is the diameter of the largest hailstone ever recorded.

Sukkur City in Pakistan is one of the most humid places in the world with 30 °C dew point & a felt air temperature of 65 °C.

A study showed that a small thunderstorm system holds more than 10 million tons of water.

No two weather patterns are completely alike.

Some weather models assimilates data obtained from more than 25,000 weather stations.

Why The need to Measure Humidity?

As described above, the daily weather fore-cast relies on the precise measurement of weather parameters. The science of numerical weather prediction aims to describe the daily hydro-logic cycle in numbers – humidity plays an important role in this – data errors will multiply during calculations.

Humidity values influence weather calculations e.g. through the water vapor balance equation – this formula expresses the influence of humidity through rain & condensation, and vice-versa.

Incorrect measurement or incomplete humidity data directly leads to wrong predictions of a huge number of weather phenomena; this can include the condensation altitude of clouds, locations of hyetal regions, fog layers and storms.

In 1999, incorrect data sent by a weather station in Nova Scotia, Canada led to an incorrect forecast for Hurricane Lothar two days before it hit Central Europe. Authorities were insufficiently prepared to alert people in time.

hurricane-ivan_200_600x450
What is the Rotronic Solution?

Rotronic products are used in weather stations around the globe. They provide temperature & humidity data continuously with high accuracy even in demanding environments.

Rotronic manufactures a range of meteorological probes and weather shields to meet the standards required by meteorological organizations.

Philip Robinson

Rotronic UK

Calibration, Sensors, Training

A relative humidity sensor for any application?

Leave a comment

As we continue to measure relative humidity in more and more environments with ever increasing accuracy demands, we are pushing the humble capacitive humidity sensor into new realms.

Accuracy, drift, operating range and chemical resistance are key challenges for the relative humidity sensor industry. Our sensor experts work hard to develop new polymers and construction methods to ensure the best performance. At the same time advanced electronics and probe housings enable digital calibration and complex temperature corrections to further increase accuracy and performance. A final and often neglected part of ensuring a relative humidity probes performance is its filter. The correct filter ensures fast response and environmental protection. Filters also offer mechanical protection and eliminate damage caused by extreme airflow.

However understanding why sensors fail is often difficult to predict or understand. In many cases the chemicals and contaminants that sensors are exposed to are unknown. In these situations often selecting the best sensor can only be achieved through mutual relationships built around quality support and service.

In the UK we have worked closely with many customers and in combination with our Swiss technical divisions to select and develop solutions for some highly aggressive and challenging environments. Some of these projects are examined below in more detail.

Hydrogen peroxide vapour sterilisation.

– Hydrogen peroxide vapour is used to chemically sterilise environments and products by generating a vapour of toxic Hydrogen Peroxide. When the humidity reaches the dew point of the surfaces condensation forms sterilising all surfaces. However the chemicals are also highly aggressive to humidity sensors and constant cycles of saturation worsen the effects.

– Making use of Rotronic’s specifically designed H2O2 resistant sensor as well as additional conformal coating to protect exposed connections in further combination with improved customer understanding around handling and storage, has resulted in a solution that has exceeded customer expectations. Importantly, whilst this was not achieved first time around, through a partnership driven towards the end goal we achieved success.

Chemical damage Chemical degradation on the sensor surface
Commercial composting.

– Accelerated commercial composting is an impressive sight to see. The chemical and biological processes occurring are complex and surprisingly aggressive. The wrong materials can literally become part of the final compost if you are not careful. Chemically resistant sensors help to provide some longevity to instruments but one of the key areas requiring extra attention is around cable and filter design. Modifying a standard industrial grade sensor with bio-resilient cables ensures the probes are not eaten alive!

Highly accelerated life testing.

– As a supplier to many chamber manufacturers and companies providing testing services this is a common application. Chambers are cycled between high and low temperatures and humidities to simulate many years aging over a short period of time. The same effects are happening to the humidity sensor – critical for the control or validation of the chamber conditions. Using industrial sensors with electronics isolated away from chamber space reduces the effects of the sudden changes. But also care taken placing the sensor away from humidity outlets and well into the chamber to avoid stem conduction all help to avoid the sensor becoming saturated as temperature cycle – which is one of the main causes for corrosion and drift. Finally, careful filter maintenance is always important.

Swimming pool monitoring and control.

– Our featured image shows chemical formation on a non-Rotronic sensors connections. Rotronic uses inert metals in the sensor design to reduce the re-activity of the sensor to chemicals in the environments. Swimming pools have a mix of high humidity, chemicals and high temperatures which work together to corrode unprotected electronics. Sensor location is key to avoid direct exposure to spray and neat chemicals. Suitable filters and if required chemical resistant sensors have proven highly successful where other instruments have failed.

So you can see not all applications are easy and we have not even begun to explore the basic issues of accurate measurement and control present with every humidity sensor installation. However our belief and aim is that through communication and partnerships we can provide the right product to ensure the desired mix of performance, resilience and price for our customers – it’s not easy but it makes life interesting!

Dr. Jeremy Wingate

Rotronic UK