Field Testing the new HL-1D Compact Logger – Up the Matterhorn!

Last week Rotronic launched their latest small compact temperature and/or humidity data logger!

HL-1D Compact Logger UK RRP £73

With the Friday off work myself and a friend thought how better to test the impressive little logger than slinging it in a pack and carrying it up through sun, fog, snow and rain on an audacious weekend attempt to climb the 4478m Matterhorn in the beautiful Swiss Alps (I confess my friend could not care less about the logger aspect but was certainly up for the climb).

Hornli Ridge of the Matterhorn 4478m

With no time for acclimatization, the climb would be grueling enough without carrying additional instruments, but thankfully the HL-1D is very compact and light. It has 3 year battery life, can store 32,000 readings and has high measurement accuracy of ± 3.0% RH and ± 0.3 °C. Of course the logger is designed more for monitoring office and work spaces,  transportation of products, production and storage environments, still we though it wise to push it to its limits!

Due to very poor conditions on the mountain we planned to overnight in a small hut at 4000m. So with our packs loaded we set off from the 2000m high gondola station above the beautiful village of Zermatt. But first ensured we were well fueled with ‘Apfel Strudel’ and coffee!

Breakfast HL-1D
Breakfast of kings!

The climb itself started at 3000m and the temperature quickly began to drop as we gained altitude.  At nearly 4000m the temperature dropped rapidly and clouds came in (shown by a rapid increase in the humidity). Luckily the Solvay Hut at 4004m provided welcome shelter and a ‘comfortable’ 3°C temperature (much warmer inside our sleeping bags).

Start of Hornli Ridge
At the base of the route proper

The morning showed that the cold temperatures and thick cloud had turned to more heavy snow fall, making any further progress even harder. The fresh snow combined with the debilitating effects of altitude sickness meant that we (wisely) decided to head straight down (this was just a quick weekend getaway after all).

Descent - more snow
Lots more snow on the way down!

The decent was challenging and navigation difficult. Snow fall was consistent most of the day and topped off by a steady shower of rain as we made our final walk back down to the gondola station (you can see the logger showing 100%rh as the top pocket of my bag becomes saturated in the down pour).

Relaxing back in beautiful Zermatt the following day – It’s sunny now!!

Back in Zermatt and we quickly find shelter to dry off and find a good spot for a celebratory beer and hearty Swiss meal.

What of our little logger? It provides a great record of the trip. Values safely recorded through the freezing temperatures and soaking rain.
Full trace of the logger can be found below; click on the image for more detail.

Matterhorn Trace
Matterhorn Trace

If you would like more info on the latest compact logger click here or for any other measurement queries please do not hesitate to contact us!

Dr. Jeremy Wingate
Rotronic UK

Technical Note 1 – Digital Integration of Rotronic devices

The Rotronic HygroClip2 was launched around four years ago and is used as standard with most of our devices. Underpinning the HygroClip2’s performance beyond the Rotronic sensor element is some impressive technology.

The Airchip3000 is the chip that provides high resolution measurement of the raw sensor outputs, temperature compensation and calibration correction tables which ultimately provides the high accuracy measurements our customers demand.  In addition, the Airchip provides digital and analogue communications. All the Rotronic instrumentation communicates digitally to these probes but these interface methods are possible without using a Rotronic handheld/logger/transmitter etc.

Lets explore what is possible…


Devices can be connected to your software or systems via USB, Ethernet, Serial or Wireless depending on the physical connections available. The AirChip itself has a simple RS232 output so additional hardware will be required for for anything but direct RS232 interface (to a Raspberry Pi GPIO for example).

Rotronic DLL

The Rotronic DLL provides a link between Rotronic devices and your software program (as well as our HW4 software). The DLL allows you to call up all functions within our devices that are accessible via our software. We have several example packages to make developing your own systems easier including;

– C++
– Visual Basic
– LabView
– Excel

The DLL can be integrated into wider software systems, if you have sufficient technical know-how. For example using using ctypes in Python allows the integration of Windows DLL. Python programs can then be used cross platform (Windows, Mac and Linux etc).

This approach is typically used when integrating our HC2 range of probes via our AC3001 Probe-USB converter cable. This way you can utilise our highest accuracy probes in a simple and efficient manor without any loss of accuracy due to digital-analogue conversions. It is also possible to quickly add the measured values into your existing projects. This is how our HygroGen2’s Autocal system communicates to the Rotronic probes during automated calibration and adjustment runs.

Example programs and DLL itself can be downloaded here

If you require support integrating our sensors into your systems please do not hesitate to contact us!

Direct Device Interface

In certain situations utilsing our DLL may not be appropriate for your project. So it is also possible to directly communicate with the Airchip3000 devices avoiding the DLL and using direct protocol commands. This is often a far simpler method and more commonly used when integrating to industrial systems.

With Ethernet and Serial devices communication if very easy using a terminal program (eg Putty) or direct from your Linux terminal (For USB some extra step are required explained at the end of this article).

1. Connecting to Rotronic devices via Putty (!!! USING USB? READ THE NOTE AT THE BOTTOM OF THIS POST !!!

Firstly, you simply need to connect to the relevant comm port or IP Address and send your commands. Serial interface settings are detailed below. For Ethernet simply use RAW connection and select port 2101 or use Telnet with Port 2001 (you will need your devices IP address)

Step 1 – Setup Serial Settings in Putty

Putty Setup

Step 2 – Force Echo On / Line Editing
I strongly recommend changing the Terminal settings to Force Echo (so you can see what you type and edit it)…

Putty Setting Echo

Step 3 – Connect
Now simply open your session…

Putty Open

All Airchip devices will respond to the command below, an example response is shown from a HC2-S probe.

Sent Command
{ 99rdd}

Return String
{F00rdd 001; 36.30;%rh;000;=; 24.30;°C;000;=;nc;—.- ;°C;000; ;001;V2.0-2;0061176056;HC2 ;000;C

Explaination ( “;” separated values)
F = Device Type
00 = RS485 address
rdd = command
001 = Device type

36.30 = value 1
%rh = value 1 units
000 = value 1 alarm condition
= = trend

24.30 = value 2
°C = value 2 units
000 = value 2 alarm condition
= = trend

nc = calculated value selected
—.- = calculated value
°C = calculated value units
000 = calculated value alarm condition
= calculated value trend

001 = hardware version
V2.0-2 = firmware version
0061176056 = serial number
HC2 = device name
000 = sensor alarm
C = checksum

Important Note! Using USB interface with Putty

By default all Rotronic USB interface cables will link to the Rotronic driver and try to use the DLL. However if you configure the cable to be a Virtual Comm Port you can use the simple serial connection method described above! So you can see every device  connection type can be interfaced using this method 🙂

To do this you need to force windows to use the standard FTDI driver and setup the Virtual Comm Port.

Step 1 Install FTDI Drives

Select the relevant drivers from this page for you OS

Step 2 – Force Windows to use new driver

Go to device manager (Control Panel, System, Device Manager)

1 – Click Update Driver
2 – Select Browse my computer for Driver
3 – Choose ‘Let my pick from a list’
4 – Click Have Disk
5 – Go to the FTDI folder and click  ftdibus.ini
6 – Select the USB Serial Port

Now you will see a new USB Serial Port in Device Manager under Ports (COMM AND LPT) – right click and select properties. Ensure the Port Settings are as below.

Baud rate : 19200
Data bits : 8
Parity : none
Stop bits : 1
Flow Control : none

You can now use the Virtual Comm Port in putty or other projects.

In my experience with bespoke software packages for a single device type the terminal connection is very simple.

For example a simple Python code to communicate with an Ethernet device is below…

session = telnetlib.Telnet(, 2001, 0.5)
except socket.timeout:
print (“socket timeout”)
session.write(“{ 99RDD}”.encode(‘ascii’) + b”\r”)
output = session.read_until(b”/r/n/r/n#>”, timeout )

We will look at direct interface to the AirChip and available protocol options next time!

Comments or queries – let us know!!

Dr. Jeremy Wingate
Rotronic UK

CO2 Monitoring in the Beverage Industry

The Carbonating Process

Everybody loves a refreshing sparkling drink during the summer heat. CO2 does not only bring the bracing sparkling effect into your drink but even helps to conserve the beverage. A chemical reaction of CO2 and water forms carbonic acid which has an antibacterial effect. All well known soft drinks come with the right fizz.

The beverages are treated with a carbonating process just before the final bottling or canning. Carbonating systems mainly consist of a booster pump, a CO2 saturator, a carbonating tank and an optional CO2 analyser to check the carbon acid content of the final product.

With the aid of a booster pump the beverage mixture is conveyed to the saturator which works according to the Venturi principle. An optimising control keeps the flow velocity through the saturator within a constant working range. This generates a partial vacuum at the smallest cross section of the saturation which causes a reduction of the pressure level. This suction effect then mixes the CO2 with the beverage liquid. The short-time increase of the flow velocity guarantees a fine distribution of the gas and homogenous mixing.

The process essentially depends on the tank pressure which has to be set slightly higher then the saturating pressure of a specific product. Right after that, the drink is ready to be bottled automatically to preserve its texture.


CO2 saturator in a carbonating stage of a bottling line

Why the need to monitor CO2 in a beverage plant?

Carbonating processes use most of the CO2 in the beverage industry. But beside that the gas also occurs during fermentation or it is used for refrigeration – so CO2 is omnipresent in such facilities.

High concentrations of CO2 in closed areas where workers attend to their jobs can become a lethal risk. Extensive CO2 levels can lead to bad headaches, drowsiness, unconsciousness and even sudden death. A CO2 level above 5000ppm is considered as alarming. The gas can neither be recognised by its odour nor by its visual appearance. Soft-drink factories or breweries therefore require an accurate CO2 control and alarm system to maintain their high standard of operational safety.


To assure hygienic conditions and to reduce the risks of CO2 incidents, bottling lines which fill carbonated drinks are often operated in separated areas of a factory. There is a controlled loss of CO2 during the bottling or canning process of sparkling drinks which is minimal, but the amount adds up considering that industrial lines are able to fill up to 30.000 bottles an hour. With each filling a tiny amount of CO2 gets exposed to the surrounding atmosphere.

Factories require big amounts of CO2 which is delivered and stored in gas cylinders. During transport or storage there is always the risk of a thin crack occurring and that gas escapes unnoticed. Drinks which are not meant to be carbonized such as beer or wine also emit CO2 during the fermentation process. The gas needs to be release controlled. Also here leakage can be a danger and CO2 sensors help to keep control of the atmosphere.

This small insight shows how beverage manufacturers depend on reliable CO2 monitoring systems!

Candice – Sales Support

BlogShot – Rotronic High Precision, Fast Response Sensors for Temperature & Humidity Monitoring in Data Centres

There has been a rapid increase in large stand-alone data centres housing computer systems, hosting cloud computing servers and supporting telecommunications equipment, they are crucial for company IT operations around the world. Data centres must be extremely reliable and secure; many are wholly remote facilities.

Air conditioning is essential to maintain temperature and humidity levels within tight defined tolerances, thus ensuring the longest possible service life of the installed hardware.

Precise temperature and humidity measurement with fast reacting sensors is an absolute requirement. This increases energy efficiency whilst reducing energy costs. Additionally, data centre managers need to be alerted to even a small change in temperature and humidity levels. A separate monitoring system with networked alarms using fast reacting temperature and humidity sensors is installed.

Rotronic ‘standard’ HC2-S interchangeable temperature and humidity sensors are regularly specified for monitoring & controlling conditions in data centres due to their high precision and fast response with long-term stability. Used with a HygroFlex5 measurement transmitter analogue (scalable) or digital outputs are available exactly as required for interface with control systems. The loop can be validated electrically in minutes saving a significant amount of time. Probes can be exchanged rapidly when service work or periodic calibration checks are required.

Contact Rotronic for full product information

Tel: 01293 571000  Email:

Incubator for the electronics of the future – Rotronic Success Story

No extraneous sounds, vibrations or electromagnetic fields find their way into the noise-free lab at the Binnig and Rohrer Nanotechnology Center in Rüschlikon. Moreover, a temperature sensor ensures that experiments on new switching elements for computer chips are not affected by temperature fluctuations. 

Today, a single computer chip contains over a billion transistors, a far cry from the ten transistors in the first integrated circuit in 1958. In the intervening years, the structures have become so small that individual layers are just a few atoms thick. This has created a new problem of electrons flowing between layers. In order to prevent this from happening, researchers are endeavoring to reinvent the transistor and to explore new types of components.

The solution lies in silence 

Switzerland is home to a world-renowned laboratory in which scientists are working on the transistors of the future: the IBM research laboratory in Rüschlikon. The location’s easy accessibility is not exclusively advantageous: when a truck passes by, it causes the samples to shake under the electron microscope. In 2011, the Binnig and Rohrer Nanotechnology Center opened six integrated laboratories with exceptionally high protection against external factors: the noise-free labs. They are built directly on rock, the actual measurement set-ups mounted in turn on concrete blocks that float on a cushion of air. Forty-ton trucks can now race by without vibrating the sample. Another problem is noise. To keep it out, the labs are equipped with thick doors. Even the scientists present were too loud and were obliged to control the experiments from a separate room.

Precise room temperature

A temperature difference of just a few degrees would be capable of moving a sample by several 100 nanometres per hour with disastrous consequences for structures in the range of 1 – 50 nanometres. A sensor is therefore used to measure the temperature and air humidity. IBM is using a Rotronic transmitter capable of measuring temperature to 0.1 °C with absolute accuracy for this purpose. This corresponds to the maximum temperature drift permitted in the laboratory over a 1-hour period. At the same time, the sensor measures the relative humidity of the air which is required to remain within 35 and 55 %RH and not fluctuate by more than 5 %RH. The sensor is even capable of measuring the air humidity to exactly 0.8%RH thanks to an integrated chip.

Top-ranking labs

Researcher Heike Riel makes good use of the quantum effects to develop small transistors that are also highly energy efficient. Instead of an operating voltage of somewhat over 1 V commonly employed today, they would work with voltages of less than 0.5 V. Rolf Allenspach aims to utilized electron spin: spin-up corresponds to a logical 1, spin-down to a logical 0. The chief attraction of this is that much less energy is required to change the spin than to displace the electron as is the case in transistors today.

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