Monitoring ambient conditions involves more than just measuring temperature and humidity. Many industrial processes, such as those in the chemical, pharmaceutical and food industries, require control over other factors, too. The same applies to air conditioning and indoor heating systems.
Sensirion is a renowned supplier of a wide variety of sensors. Thanks to its extensive experience in the market, the manufacturer has developed many design solutions, e.g. exceptionally universal and precise modules, such as the ones from the SEN5x series presented below. They are integrated sensors that can measure temperature, humidity and particular matter, as well as analyse air composition. The SEN5x series consists of several products, the specification and functionality of which we will describe below.
This article covers topics such as:
- Main characteristics of the Sensirion sensors
- Concentration of particles and dust in a Clean Room
- VOC Index, unpleasant odours and air quality
- Nitrogen oxide and human health
- Additional accessories in the SEN5x series
General information
The SEN5x sensors are enclosed in a 52.3×43.3×22.3 mm housing, which is a surprisingly small size, considering its contents. It has a fan to drive air into the measurement chamber, as well as an integrated laser sensor which accurately estimates the number of particles in the pumped gas. The models from this series are also equipped with additional sensors (you can read more about these below). Since the circuit is based on a specialised IC, the products are pre-calibrated and ready for action.
Voltage from 4.5 V to 5.5 V DC (available in most microprocessor systems or systems controlled by a microcontroller) is required to power the device. Communication with the central unit is carried out via a digital, serial I2C interface, which can be easily implemented in any circuit. It should also be noted that during idle time (when no measurement is performed, and the fan is not moving) the current consumption of the module drops to as low as 1 mA (depending on the model), and does not exceed 100 mA in short periods of time (i.e. with the fan running and during tests). With such values, the SEN5x modules can be installed in devices that operate remotely and are powered by batteries or renewable sources, such as sensors in the industrial and consumer IoT segments.
Sensors
  Jumper wires
  Full set
Available versions of SEN5x
The SEN5x series includes three models and two sets. The basic version of the (SEN50-SDN-T) sensor measures only volatile particles concentration in the range of 0…1000 μg/m3. The size range of the measured particles is adjustable and can take diagonal values from 0 µm to 1 µm, 2.5 µm, 4 µm or 10 µm. Information on the presence and density of such elements in the environment is particularly important in spaces such as clean rooms, where electronic components are manufactured.
Temperature and humidity, organic compounds
Apart from a laser sensor, the more advanced model of the (SEN54-SDN-T) module is fitted with additional circuitry, thanks to which it also measures temperature and relative humidity. Its greatest asset is the detection of VOCs, or volatile organic compounds, derivatives of hydrogen, chlorine, sulphur or fluorine, among others. Their higher concentration is undesirable ‒ not only because of their effect on human health (carcinogenic properties of benzene and formaldehyde), but also because of the unpleasant odour  that they can cause. This is why VOC (sometimes referred to as VOC Index) monitoring is considered an important element in air quality testing, for example in HVAC systems, in offices and residential buildings.
Nitrogen oxide
The most complex product in the series is the SEN55-SDN-T. And again, this model has an expanded functionality in comparison to the ones described above, this time thanks to a nitrogen monoxide/nitrogen dioxide sensor. These are among the most harmful gases polluting the atmosphere. In the case of NO2, it actually goes as far as posing a direct threat to human health or even life, especially when a person suffering from asthma or COPD (Chronic Obstructive Pulmonary Disease) is exposed to higher concentrations of this compound in its free state. Therefore, the applications of the SEN55-SDN-T include professional equipment in chemical processing, medicine, etc.
Additional products
Additionally, the series includes two other items, the first one being a set of SEN5X-JUMPER-WIRE connectors, which allow you to lead the communication and power lines from the socket located in the sensor to standard pin connectors (so-called goldpins). Such a wire can prove to be very useful, especially at the prototyping stage. The other item is a set that includes the SEN55-SDN-T sensor and two types of jumper wires: with a pin connector or with a RJ-45 plug.
