Tag Archives: sensors

CO2, Humidity, Process, Sensors, Temperature

Energy Efficiency and Indoor Air Quality

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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.

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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

CO2

CO2 in Garages and Tunnels.

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Modern vehicle engines emit many harmful substances, including carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx), hydrocarbons and some 20 other gases. It is known that all engines produce CO, particularly at cold start. To protect ourselves from this toxic gas, vehicles are installed with catalytic converters. This means that a warm running modern engine with converter generates 140 times more CO2 than CO.

catalytic_converterCatalytic converters convert a lot of the CO produced by an engine into CO2.

Facts and Figures

The longest tunnel in Switzerland will be the Gotthard Base Tunnel (under construction) that will be 57km long. The tunnel is a railway tunnel.

The longest car tunnel in the world is located in Norway, the Laerdal tunnel, 24km.

The LEP tunnel in Cern, Switzerland/France is a 26km circular ring.

Why the need to measure CO2?

Old vehicles (pre-catalyst) generate a lot of carbon monoxide pollution, to solve this, modern vehicles were installed with catalytic converters. Catalytic converters are not very efficient during cold start up but once warm they can convert CO to CO2 very effectively. This means modern engines emit much higher quantities of CO2 than CO. It is well-known that CO is extremely toxic but CO2 in high levels can also be hazardous to health. To ensure healthy air quality it is important to provide excellent ventilation in garages and tunnels, however running a ventilation system constantly is inefficient especially when few cars are running at a time.

SAM_3014Levels of CO2 in large indoor car parks can become extremely dangerous if not properly controlled.

In garages and tunnels vehicles can be operating in both warm and cold conditions, therefore it is important to measure both CO and CO2 to ensure a safe environment. Today there are laws around the measuring of CO – the maximum allowed value is 35 ppm. There are however, currently no rules on measuring CO2 but this is equally as important.

How does it work?

A meter can both control and alarm locally, as well as being part of a larger complete system. This application is similar, for example, to the ventilation requirements in a classroom.

The ventilation need depends on the number of cars running in a garage or tunnel instead of the number of students in a classroom. The sensors usually used to measure CO2 and CO in public garages and tunnels are capable of covering an area of around 250 m2.

Reduced Costs

A study was made in a garage containing 77 parking places and covering an area of 1,445 m2. The study showed that using sensors to control the ventilation reduced the fan operating time by 90% compared to constant running. The electricity cost was about €0.09 per kW/h (including energy tax and VAT) and the fan used 1.5 kW/h in operation. This meant that the demand-control solution produced an energy saving, per month, of 970 kW/h, and a resulting reduction in running-costs of ca 85.32 €/month. If all residential garages were equipped this way the sum of energy saved would make for a considerable benefit to society and the environment. A larger garage would have saved even more money thanks to the controlled ventilation system.

c700x420Ventilation plays a vital role in keeping in door parking spaces safe, especially when busy.

Another benefit is fewer people suffering from CO or CO2 poisoning being admitted to hospitals. As well as being good for the health of the general public, This helps reduce the costs of health care to the government.

Phil Robinson                                                                                                           Rotronic UK

Calibration, Humidity, Process, Sensors, Temperature

Temperature, Humidity and Ceramic drying

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Introduction

Ceramic drying is one of the most important processes in ceramic production technology. Quality defects of ceramic products are caused by improper drying. The drying affects the quality of the finished product, the throughput but also the overall energy consumption for ceramic manufacturing enterprises. According to various statistics, generally energy consumption during drying processes represents 15% of total industrial fuel consumption. However within the ceramic industry, the energy consumption used for drying accounts for a much higher percentage of the total fuel consumption. Therefore energy saving within the drying process is extremely important for all enterprises. Drying speed, reducing energy use , ensuring high quality products and reducing  pollution are all  basic requirements for any ceramic manufacturer today.

Measurement and Control in Ceramic Dying

Ceramic production is done through several main processes: casting, drying, glazing, firing…

The casting and drying are important processes for ceramic. A forming workshop is equipped with an intelligent control system. The control system regulates the relative humidity value using information provided via room and process sensors. Sensors have to measure accurately ad repeat ably despite the challenging and often dusty conditions. Humidification and dehumidification processes require substantial energy so tighter control is a huge energy saver for these industries.

A constant temperature is also achieved via the intelligent control system. With a stable temperature and stable relative humidity within the workshop, manufacturers ensure the quality of  the ceramic body drying.

After stripping the body from the cast, the body contains a very high relative humidity level. During the drying process, the body may crack or deform due to the speed in which the product is dried (volume and shrinkage) which ruins the product and decreases the throughput.

Exactly this part of the process has become a major bottleneck within the production process of ceramic products.

In a casting workshop, stable environments can reduce the cracking and deformation effectively. It also improves the throughput rate of semi-finished products and shortens the drying period, also prolonging the life frame of the  plaster cast.

So constant temperature and  relative humidity according to the set values will help all factories to improve the throughput, reach an optimal drying speed and deliver the best quality results available.

How can we help?

Rotronic provides a range of instruments for environmental monitoring and control.

Rotronic HC2-IC industrial temperature and humidity probes, are successfully working in these tough applications, the probes are installed on the roofs of drying chambers and resist chemical pollution. With a flexible  HF5  transmitter, the outputs can be set to the customers requirements.

With both digital and a range of analogue outputs available as well as several probe mounting options, products can be selected for all applications.

Measurement data can be viewed on HF5 with display or remotely via HW4 software. Ease of calibration and sensor replacement ensures down time is kept to an absolute minimum.

Dr Jeremy Wingate
Rotronic UK

 

CO2, Sensors

CO2 and Indoor Air Quality (IAQ)

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Indoor Air Quality in General

The quality of the air in a room can greatly affect the health, productivity, and well being of any occupants. Previously the temperature and humidity of indoor air were considered as the most important parameters contributing to air quality, but there are several other factors which must be taken into account.

Indoor Air Quality (IAQ) problems are very often caused by gases or particles released into the air by pollution sources. This can be avoided by carefully selecting the materials which are to be used inside dwellings, offices, classrooms, gymnasiums, hotels, shopping malls, hospitals and in all en-closed spaces which are inhabited. But there is another source of air pollution, which cannot be avoided. this other source is people themselves. Every time a person exhales, CO2 is released. Inadequate ventilation may increase CO2 concentration to an unhealthy or even life-threatening level.

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CO2: made up of 2 oxygen atoms, double bonded to a single carbon atom.

The most important control parameters for a good Indoor Air Quality are temperature, relative humidity and CO2 concentration. If these values are used with an intelligent air conditioning system, an energy efficient air supply can be used to produce a high quality atmosphere.

Facts & figures:

CO2 is a naturally occurring molecule consisting of two oxygen atoms and a single carbon atom.

At standard temperature and pressure CO2 is a gas, invisible and without any smell or taste.

CO2 is 50% heavier than air and has no liquid state under atmospheric pressure.

In the earth’s atmosphere CO2 has a concentration of 390 ppm by volume.

The worldwide industry produces approximately 36 billion tons of CO2 per year.

Industrial activities are responsible for an increase of atmospheric CO2 concentration and thus for an increase of global warming (greenhouse effect).

Influence of CO2 on Humans

Only a small amount of the atmosphere is made up of CO2, the prevailing components are nitrogen and oxygen. The natural outdoor atmosphere CO2 level is approx. 390 ppm. Increasing this concentration causes several symptoms of poisoning, ranging from drowsiness at around 1´000ppm to unconsciousness and even death at above 10´000 ppm. Even if a  rise in CO2 concentration has not yet severely influenced the health of people, it may reduce their productivity, efficiency and well-being.

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Some of the possible health effects

How to Measure CO2

The most common measuring method for CO2 concentration nowadays is based on a spectroscopic principle. Sending infrared light (IR) with a wave length of 4.23 μm through a gas sample. CO2 molecules in the sample absorb the light at this wavelength. an IR sensor is then used to detect any changes in the energy levels of the light after passing through the sample. The more C)2 in the sample, the more of the light that will be absorbed, and the weaker the IR signal will be when it reaches the sensor.

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Example of an IR CO2 sensor

The sensitivity of a CO2 sensor increases with the length of the light path through the sample gas. Thus the sensor used in Rotronic CO2 measuring devices makes use of multiple reflections of the IR beam on the walls of the probe chamber. this means the small CO2 sensor (2.5 cm x 5 cm) has a measuring path length of 12.5 cm and is accordingly sensitive. This type of sensor is called a NDIR (Non Dispersive Infra Red) sensor. This means that a broadband IR light source is used and the measured wavelength is filtered out at the end of the beam in front of the IR detector.

Why the Need to Measure CO2

New energy efficient demands lead to more airtight buildings and ventilation being completely turned off at night. Intelligent HVAC systems must be able to adapt themselves to situations with changing occupants of rooms. One answer is Demand Controlled Ventilation (DCV) with built-in CO2 sensors. By using DCV, huge amounts of energy can be saved without any drawback for the occupants. According to a study of the UN Climate Panel 40-50% of world energy is used in buildings. Only the adoption of the EU Directive on Energy Efficient Buildings would result in saving 30-45 MT of CO2/year. As HVAC (Heating, Ventilation and Air Conditioning) is responsible 40-65% of energy usage in commercial and public buildings, a balance between comfort and energy saving must be found.

HVAC

A large HVAC system

One example demonstrates the evidence of CO2 controlled room ventilation. The exhaled air of a human contains up to 40´000 ppm CO2. In one hour a person breathes out 15 litres of CO2. Thus in a classroom with a volume of 200 m³ occupied by 25 pupils the CO2 concentration increases in one hour by 1´875 ppm!

Especially in wine cellars, breweries, the beverage industry and other industries in which CO2 may be produced or processed the constant measuring of CO2 concentration is absolutely vital to prevent a deadly threat to the employees. This is not only a rational procedure but is also enforced by official regulations in nearly every developed country.

Philip Robinson                                                                                                       Rotronic UK

Meteorology, Sensors

Wind Turbines

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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.

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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, News

Humidity Control & Pharmaceutical Tablet Coating

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Tablet coating in general

Pharmaceutical tablet coating involves the application of a coating composition to a moving bed of tablets with the use of heated air to facilitate the evaporation of the solvent. Several different types of coating are typically used.

Tablet Coating
Tablet Coating Machine
  • Sugar-coated tablets are coated with a coloured or an uncoloured sugar layer. The coating is water soluble and quickly dissolves after swallowing. The sugar-coating protects the encapsulated drug from the environment and provides a barrier to objectionable tablet taste or odour.
  • Film-coated tablets are compressed tablets coated with a thin layer of a polymer that forms a skin-like film. This is usually coloured and has the advantage over sugar coatings  that it is more durable, less bulky, and works faster at the desired location in the gastrointestinal tract.
  • Enteric-coated tablets have delayed release properties. They are designed to pass unchanged through the stomach to the intestines, where the tablets disintegrate and allow the drug to dissolve and start its effect. Enteric coatings are used when the drug substance itself would be destroyed by gastric acid or is irritating to the gastric mucosa.

Facts & figures:

Aspirin is one of the most used drugs in the world – approximately 35,000 metric tonnes are produced annually, enough to make over 100 billion aspirin tablets.

Americans consume 80% of the world`s supply of painkillers — more than 110 tons of pure, addictive opiates every year.

How can accurate measurements help?

Environmental control is the practice of managing the temperature, humidity, air circulation, ventilation and air pressure of a given space. Within certain types of pharmaceutical manufacturing processes, precise environmental control can help limit inefficiencies and potential problems.

Pharmaceutical tablet coating is one such application. Inefficiencies during the coating process may result in contamination and tablet impurity in the form of tablet-to-tablet colour variation, surface pitting from over-wetting, twinning due to spray drying, cracking or peeling. Most of these problems can be overcome by better control of the environment within the process. Over-wetting, for example, occurs when the coating hits the still wet tablet surface and the surrounding air does not dry it quickly enough. Another example involves spray drying, when the coating hits the tablet surface after the moisture has been removed resulting in poor adhesion of the coating.

In the case of incorrect cooling and drying of the sugar solution, a rough, translucent and uneven coating may be produced.

Since the required environment for a perfect coating strongly depends on the composition of the tablets, many pharmaceutical manufacturers have scientists who perform experiments to determine the ideal coating procedure including temperature and humidity levels. Once these specific requirements are determined, the set-points can be configured at the controller to enable the precision tablet-coating machines to work at optimal performance.

spoonfull of medicines
A spoonful of perfectly coated tablets!

Tablet Coating Benefits-Summary

  • covers the unpleasant taste, odour and colour
  • provides physical and chemical protection for the medicine (light, moisture and air)
  • controls the release of a drug (enteric coating)
  • improves the appearance of tablets
  • easier to swallow the tablets
  • assists and facilitate the identification of a drug
Dr. Jeremy Wingate
Rotronic UK
CO2, Humidity, News

Greenhouses and environmental control

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The idea of growing plants in environmentally controlled areas has existed since Roman times. The emperor Tiberius ate a cucumber-like vegetable daily. The Roman gardeners used artificial methods (similar to the greenhouse system) of growing to have the vegetable available on his table every day of the year.

The next step from the conventional greenhouse as we know it today will be the introduction of “vertical farms”. Currently, sophisticated so called “plantscrapers“ are being planned or are already under construction in Sweden, Japan, China, Singapore and the United States.

Skyscraper

Skyscraper farming might yet be a possible answer to the question of how to feed the nine billion people that are expected by the middle of the century. These types of green-houses have a tightly con-trolled level of temperature, humidity & CO2, sophisticated watering systems and in addition to sunlight, advanced artificial LED lighting that is specifically designed and installed for each plant family. This way, the crops grow much faster and very efficiently all year round. It is estimated, that the Swedish plantscraper that is planned to be 54m high, will produce thousands of tonnes of food a year, enough to feed up to 30,000 people.

Facts & figures:

  • Tomato is the second most important commercial vegetable crop after potato. Current world production is about 100 million tonnes produced on 3.7 million hectares.
  • In the year 2000, per capita consumption of fresh tomatoes in the U.S. was 17.8 lb,/ 8.73 kg.
  • About 85 percent of the world’s soybeans are processed, or “crushed,” annually into soybean meal and oil. Around 98 percent of the soybean meal that is crushed is further processed into animal feed.
  • The Food and Agriculture Organization of the United Nations (FAO) reports that world production of carrots and turnips (these plants are combined by the FAO for reporting purposes) for calendar year 2011 was almost 35,658 million tonnes.

Why do we need to measure humidity?

Greenhouse humidity levels are important both in prevent-ing plant diseases and promot-ing healthy and strong plant growth. High humidity can promote Botrytis and other fungal diseases. High humidity also restricts plant transpira-tion, which in turn limits evapo-rative leaf cooling and can lead to overheating of plant foliage. If high humidity persists for a long time, the restriction of transpiration can limit the “transpiration stream” of nutrients and can lead to nutrient deficiencies.

Low humidity levels are best avoided because these may increase foliar transpiration to the extent that the root system cannot keep up. Humidity is perhaps the most difficult of the greenhouse conditions to control. Most growers simply aim to avoid the extremes of humidity. Over most temperature ranges, a greenhouse humidity of 50 – 85 %rh is generally safe. Low humidity can be managed with the use of misters and foggers. It is also useful to shade plants under conditions of low humidity to reduce the rate of transpiration.

Transpiring plants add water vapour to the greenhouse air, increasing the humidity inside the greenhouse. Therefore, managing high humidity starts with ventilation control. Replacing warmer, humid greenhouse air with cooler, drier external air. Ventilation also involves significant energy losses, and therefore ventilation must often be accompanied by heating. Therefore, lowering greenhouse humidity with a combination of ventilation and heating increases energy costs significantly.

Candice 
Area Sales Manager
Humidity, News, Process, Sensors

The Great British Bake Off… It’s all about humidity!

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Bread – The stuff of life!

Most of us have a never ending choice of the most delicious breads, cakes and pastries to please both the palate and the eyes. We have become so used to this diverse range of bread and baked products, but do you how bread originally came into existence?

The interesting history of  what is now called the “staff of life”, bread, and the making of it, started in comparatively recent times.

At the very beginning of recorded history there was the discovery of fire making and thus along with light, heat could be generated. Then it was found that different grasses and their seeds could be prepared for nourishment.

Later, with the combination of grain, water and heat, it was possible to prepare a kind of dense broth. Hot stones were covered with this broth or the broth was roasted on embers and “hey presto” the first unsoured flat bread was created. This ability to prepare stable food radically changed the eating habits and lifestyles of our early ancestors. They progressed from being hunters to settlers.

Facts & figures:

  • Records show that as early as 2600-2100 B.C. bread was baked by Egyptians, who it is believed had learned the skill from the Babylonians.
  • On average, every American consumes around 53 lb (24 kg) of bread per year.
  • The “pocket” in pita bread is made by steam. The steam puffs up the dough and, as the bread cools and flattens, a pocket is left in the middle.
  •  US Farmers receive just 5 cents (or less) for each loaf of bread sold.

Why the need to measure humidity?

The production of baked goods such as bread, cakes, biscuits and pastries requires a number of processing steps in which humidity and temperature play an important role.

After mixing, it is typical to divide the dough into pieces and allow it to rest for a few minutes so that the gluten network in the dough can relax allowing easier moulding, which is the next step.

If at that stage, the temperature is too hot the dough will be too sticky and cannot be easily processed further, if too cold the dough can become damaged during moulding which leads to holes forming in the bread. If the humidity level prior to the moulding process was too low a skin of dry dough can form on the dough surface. This makes it harder for the dough to increase its volume during the next
process step called proving.

Proving is the professional term for the final dough-rise step before baking, where 90% of the bread volume is achieved. To achieve consistently good dough rising results special chambers are used. These chambers can maintain the ideal environment for the yeast to grow. Depending on the yeast and flour used, temperatures between 38…42°C and humidity levels between 70…80%rh are considered ideal.

In summary, the use of quality ingredients and careful handling throughout the various stages of production will not result in a quality product  unless the dough temperature, and the temperature and humidity of the bakery are carefully regulated. Modern day bakeries use custom ventilation systems that are controlled by precision humidity and temperature sensors.

So once again the behavior of the humble water molecule is to blame! In this case for the stricken faces of The Great British Bake Off contestants as they stress about the quality of their crust and whether the dough will be cooked through to perfection!

Calibration, Sensors, Training

A relative humidity sensor for any application?

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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