Category Archives: Sensors

What is Dew Point Temperature

Our state side colleagues have put together a great FAQ technical note explaining dew point temperature in more detail!

chilled mirror / dew point mirror
chilled mirror / dew point mirror

The FAQ technical note can be accessed here and answers the following key questions!

  1. What is dew point temperature?
  2. What is frost  point?
  3. When should I choose dew point as the parameter I measure?
  4. What are the pros and cons of measuring dew point versus relative humidity?
  5. Does dew point change as the ambient temperature changes?
  6. How does pressure affect dew point measurement?
  7. What are the common technologies for measuring dew point?
  8. Isn’t dew point temperature the same thing as wet bulb temperature?
  9. How do I know which technology is best for my application?
  10. Where can I buy a dew point instrument?

Rotronic produce precision low dew point sensors for low moisture applications in addition Rotronic UK is the UK distributor for world class MBW chilled mirrors, please contact us for additional information!

Dr Jeremy Wingate
Rotronic UK

Temperature, Humidity and Ceramic drying


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


Monitoring Transportation

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:


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.


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.


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.


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.



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


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

CO2 and Indoor Air Quality (IAQ)

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.


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.



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.


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.


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

Wind Turbines

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.

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.


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

Energy Efficiency and Reliability in Modern Data Centres


Data centres are rapidly becoming the power houses of the modern world. Combined with the rise of digital industries, virtually all business operations now rely in some way on the transfer of data. As data transfer rates increase in tandem with an explosion in mobile communication the demands on data centre infra-structure are ever increasing.

It is estimated that by 2018 global data traffic will exceed 8500 exabytes (32% compound annual growth rate).

Data centres provide the infra-structure to support the transfer and hosting of data. They are often classified into 4 tiers. Tier 4 provides highest levels of redundancy, security and efficiency. For example, a Tier 4 data centre is required to have an uptime of 99.995% equivalent to less than 27 minutes downtime per year! Tier 4 sites have fully redundant systems, power supplies and biometric security. Zero downtime is the ideal as the costs incurred via end user penalties can be huge.

data centre tiers

Why the need to measure temperature, humidity and differential pressure?

Data centres must be maintained to specific environmental conditions to ensure the performance and longevity of the hardware installed. As standard, temperature must be 18-27 °C, dew point 5-15 °C dp and humidity no higher than 60 %rh. This ensures the hardware is at a suitable temperature, condensation is avoided and the chance of static build up is reduced (caused by low humidity).

A control range of ±9 °C may seem relatively broad, however 100% of the energy supplied to server hardware is converted to heat. In most data centres if the cooling system fails and servers are not shut down, heat levels will rise above a critical 35 °C within minutes or even seconds. If unchecked, temperature levels will rise causing hardware damage and can result in electrical fires.

Achieving the specified control range requires precision sensors and advanced control systems. Typically modern data centres are designed using computational fluid dynamics to ensure the very highest efficiency. Despite this it is estimated around 5% of US electrical energy used is for data centre cooling.

pue power usage effectiveness

Since 100% of electricity utilised by servers is converted to heat, theoretically a 100% efficient cooling system would require an equal amount of energy. Efficiency is measured by comparing total facility energy use, with IT equipment energy use. This is called Power Usage Effectiveness (PUE). Theoretically PUE can be 1 but typically reported values are above 2. By utilising precision measurements and design, modern data centres achieve PUEs of ~1.1!

An improvement of 0.5 in a data centre’s PUE  equates to a energy saving of ~£2.2 M & ~12,000 tonnes CO2 over 5 years (for a site with 1 MW load).


What solutions can Rotronic offer?

Rotronic provides a range of instruments for environmental monitoring and control. Reliable and precise outside air sensors and weather shields enable natural cooling to be utilised where possible.

Inside the data centres, Rotronic interchangeable HC2-S probes can provide a combination of precise, fast response temperature and humidity measurements with ease of calibration. Our latest PF4 differential pressure transmitters provide precision low drift measurements.

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

Importantly though we aim to understand your needs and build a relationship with the goal of providing an appropriate solution, combining instruments, training, calibration and ongoing support.

Dr Jeremy WIngate
Rotronic UK


Timber Drying

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.


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.


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


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


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

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


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