Category Archives: Training

A relative humidity sensor for any application?

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

New states of matter… making a mess of my slide pack

How many states of matter are there?… Hold that answer, first I’ll explain why…

We regularly provide formal and informal training, in fact it is something we  feel differentiates us, helps us learn and is a great  way to keep in contact with the industry. With a team including ex-NPL staff, Oxford graduates, PhDs, one of the best UKAS laboratories in Europe and years of combined experience in the fields of humidity, dew point and temperature  we feel we are well placed to offer these expertise.

One of the first things we discuss when learning about the principles of humidity, are the states of matter. It s vital to understand solids, liquids and gases before we can go on to vapour pressure, dew point, frost point and triple points etc.

I have yet to find someone who doesn’t know the three states but this light introduction acts as a good starting point to the deeper subject.

However, I am regularly corrected that plasma is the forth state of matter (not relevant for our discussions as such but still valid all the same). So I have corrected my slides accordingly.

What happened next, I struggled to believe at first when I was told… Apparently within chickens we can find another state of matter!! Seriously… chickens. To be exact the chickens eyeball. It is called ‘disordered hyperuniformity’ and in simple terms it is a state that has some crystal like properties and some liquid like properties.

A state of chicken
A state of chicken; Courtesy of Joseph Corbo and Timothy Lau, Washington University in St. Louis

The  arrangement of cells was discovered by researchers at  Princeton University and Washington University in St. Louis. Full details can be found here on the Princeton site. http://www.princeton.edu/main/news/archive/S39/32/02E70/

What next I thought, and where best to look but wikipedia… A quick search highlights that the four fundamental states of matter are just the tip of the iceberg.

There are; Non-classical states, Low-temperature states, High-energy states, Very high energy states … the list goes on and this is just a glance at wikipedia!

The latest (unless another has just been discovered) is the quantum droplet and apart from being the most recently discovered comes with a great picture.

Quantum Droplet
Quantum Droplet; Credit: Baxley/JILA

Part particle, part liquid, it is termed a “quasiparticle”. I wont attempt to explain it here but if you are interested is it nicely explained on the Scientific American website, which includes a link to the original Nature paper. http://www.scientificamerican.com/article/dropleton-quantum-droplet-quasiparticle/

So back to the question; how many states of matter are there? I will stick to answering that with” there are four fundamental states of matter…” I think the rest we’ll leave out of our training courses for now!

Dr. Jeremy Wingate
Rotronic UK