Frequently Asked Questions

Ilmsens developed a highly innovative technology that can replace the well-proven network analyser (NWA) measurement method in many areas. Since the NWA measurement is performed at only one frequency, which is varied one after the other, the acquisition of an entire frequency band takes a great deal of time. This requires no or only very slow changes of the measurement scenario characteristics and, thereby, limits the practical application possibilities. The measurement method developed by Ilmsens works in the time domain and can therefore measure thousands of frequencies simultaneously. This reduces the measurement time considerably and allows for the investigation of changing objects or scenarios. Especially with radio measurements the measurement of moving persons or the detection of their vital signs, for example, becomes possible.

In addition, classic NWAs are bulky laboratory equipment for stationary use and are generally large, heavy and consume a large amount of energy. This makes NWAs particularly unsuitable for mobile use when measuring radio scenarios. Our Ilmsens instruments, on the other hand, are miniaturised through monolithic integration of the RF electronics and can be used in a wide variety of locations. In addition, they consume considerably less energy, are robust against harsh measurement environments and can be operated for several hours with a rechargeable battery.

Regarding the software, the measurement data's improved information content allows for the creation of a "digital twin" for the examined process. This model is able to make predictions about the process development based on the measured values and give recommendations for action. The measurement data from the sensors, which are installed in different plants, can be linked to each other and enable further helpful conclusions on process optimization.

The high measuring speed allows measurements of inhomogeneous material samples or samples with high flow velocity, for example in bubble and flowmark/streak detection. One broadband measurement allows the direct measurement of frequency-dependent impedances and the indirect determination of other deducible physical quantities, such as the composition of a multi-component substance. This corresponds to several parallel, narrowband resonator measurements at different frequencies.

The exact costs depend on the adaptation effort and the necessary materials. Please contact us for an offer. We would be happy to receive your request.

Measurement electronics

In liquid analysis, no electromagnetic waves are emitted outside of the monitored medium, whereas in nearfield radar applications, radio regulations generally have to be met, e.g. ECC regulations. This leads to two general options for measurement electronics:

• ECC-band, frequency range: 6-8.5 GHz, conforms to Electronic Communications Committee (ECC) regulations
• Baseband, frequency range: 0.1-6 GHz, transmitted power: < 1 mW, conforms to Electronic Communications Committee (ECC) regulations

Impedance spectroscopy probe

• Dimensions dependent on the application (substance type, process requirements, etc.)
• Applicator interacts with the medium in the form of flow cells or immersion probes
• Applicator electrodes can have ohmic contact with the medium or can be realised in a non-invasive way, separated by a thin insulator (avoids direct currents, electrode corrosion, contamination etc.)

Near-field sensing

• Dimensions dependent on application and possible requirements
• Generally non-invasive measurement
• Applies broadband antennas

Data analysis
Types of data evaluation:

• Monitoring (time – detection of a change compared to before)
• Comparison (with a reference value)
• Prediction (based on machine learning)
• Recommendation (based on machine learning and additional information provided by our partners)

Yes, the sensor can be designed in a way that it can be integrated into existing processes. Depending on the type of evaluation (monitoring, comparison, prediction or recommendation), there may be requirements for the process technology that handles and, if necessary, evaluates the data amount. This can be studied through on-site visits and preliminary tests.

Impedance spectroscopy

When implementing the sensor into a process, it is important to ensure the sensor is installed at a location that allows for the measurement of a representative quantity of liquid. Stable measuring conditions with respect to physical conditions are generally advantageous. This means that effects, such as moving metal parts in the immediate vicinity, changing foam formation, or bubbles in the liquid strongly influence measurement results and should be minimal if they are not the object of evaluation.

Near-field sensing

The implementation of nearfield sensing follows the general concept of the transmission of waves. While it cannot be used to transmit through metal or large amounts of water, the technology can, however, be conveniently hidden behind plastic housing or in ceiling lining, for example.

There are several ways to ensure correct measurement:

It is possible to measure a standard scenario (e.g. demineralised water for impedance spectroscopy or a specific movement for nearfield sensing) in the beginning and later measure the same scenario and detect deviations qualitatively.

For sensors working with the machine learning algorithm, training measurements are always carried out at the beginning and the measurement results are verified by a second source. These training measurements can then be used as a reference to check whether the sensor is measuring correctly.

Impedance spectroscopy

• Sensor electrodes always use two types of material: Conductive and insulating
• Specific material combinations are possible according to application requirements (e.g. food regulations or withstanding acidic fluids)
• Passivation of electrodes with a thin protective layer, anti-fouling layer or biological functional layers is possible

Near-field sensing

• Mostly contactless measurements (over-the-air)
• Measurements where antenna is in contact with materials other than air (especially humid or salty materials)

• → Antenna requires protection against corrosion

• Direct monitoring or subsequent readout via software
• File export: Export of the measured data from the software as text, excel or graphic file
• Storage of measured values and measuring circumstances (temperature, date) in the measured data

A computer is not necessary for the actual operation of the sensors, however, the data is exported via USB or LAN connection. The evaluation of the measured data is computer-aided.

The preliminary investigations are carried out by Ilmsens employees, whereby the graphic interface of the built-in sensor measurement technology can be adapted to customer requirements and, for example, display both a (simplified) "user view" and an (more extensive) "expert view".

It depends on the type of data evaluation. Recording the data over time and comparing it with earlier values does not require calibration and is also functional with relative values.

Impedance spectroscopy

If comparisons with reference values are to be made, it is necessary to create a "library" of the measurement data from the reference substances before starting the process monitoring. If the process is dependant on temperature, the substance must be recorded in measurements that cover the relevant temperature profile.

Near-field sensing

For measurements that aim for an absolute value as a measured outcome, temperature stability is essential.

No, neither for the user nor for the test material. The sensors are operated with minimal voltages and in the case of contact measurements there is no radiation in the air. For non-contact measurements, such as near-field sensing, the power that is radiated is less than 0.1 percent of mobile phone radiation.

If the measuring ambient temperature is subject to strong fluctuations, calibration measurements for the respective processes that cover all the measuring temperatures that occur must be carried out beforehand. Furthermore, a differentiation must be made between the applicator and the measuring equipment in regard to the requirements for the measurement scenarios:

• The sensor electrodes and antennas are adapted to the specific requirements of a measuring environment
• The measuring instrument itself is currently an evaluation kit developed for an ambient temperature of 20°C. However, it can also be operated without issue in temperature ranges from 5°C to 40°C. Functionality is guaranteed at humidity up to 80%, which is non-condensing. Completely waterproof housings are also possible. (With progressing monolithic integration of the measurement electronics, the electronics can be included in the sensor electrodes at a later time.)

For further details, please refer to the data sheets or contact us directly.

Impedance spectroscopy (also dielectric spectroscopy or electrochemical impedance spectroscopy) is a non-destructive, fast and low-cost measuring method that can record electrical material parameters, such as impedance, conductivity and permittivity. These parameters are frequency-dependent and vary based on the frequency of the alternating electric fields they are measured with.

Ultra-wideband impedance spectroscopy allows for insight into the examined materials that would otherwise not be obvious at first glance. This can be interesting for users that would like to have information that goes beyond conventional sensors. Various process parameters are reflected in electrically-measured quantities and can be captured with UWB technology.

In some cases, the direct measurement of one parameter is either not possible or cannot provide the required information. In these scenarios, the information can be derived through post-processing or a combination of the measured data.

An electromagnetic (EM) wave is emitted from the applicator into a substance.
The amount of the transmitted, absorbed or reflected signal gives insight into the material properties of the substance.

The interaction between the substance and the signal is based on the atomic or molecular building blocks of the substance and the frequency of the electric field of the propagating signal.

The frequency-dependent material parameter permittivity ε_r describes the transmissibility of an EM wave through a substance and is measured over a broad frequency range with a single measurement. This allows for a differentiation between very similar substances that is not possible with a single narrowband measurement.

A typical behaviour is found for a given substance component. Just as a fingerprint can be assigned to a specific human being, a certain substance component can also be assigned to an impedance spectrum. The wider the frequency interval over which the measurements are carried out, the more clearly the assignment succeeds.

The impedance spectrum of an unknown mixture of substances is measured through a superposition of the impedance spectra of the (known) individual components and leads to an indirect conclusion for the material composition (usually through machine learning methods).

• Low measuring power; non-destructive and applicable for inorganic, organic, and biological substances
• No optical transparency required
• Inline measurement possible
• Inexpensive electronics
• No addition of contrast agents, markers or reagents
• Possibility for the electrodes to measure by coming in contact with the substance or to measure non-invasively
• Development of the electrodes for both, continuous use and single use

The main advantage is the ability to differentiate between components of a complex substance: Through ultra wideband signal measurements, the typical behaviour is found for a given substance component. Just as a fingerprint can be assigned to a specific human being, a certain substance component can also be assigned to an impedance spectrum. The wider the frequency interval (impedance spectrum) over which the measurements are carried out, the more clearly the assignment succeeds.

Two substances might be similar in a limited frequency range, but the wider the measured frequency range, the more likely it is to find differences in a specific frequency range.

Impedance spectroscopy helps to detect the composition of mixtures of substances, such as:

• The composition of liquids (e.g. milk)
• The condition of industrial processes that include liquids (foods, chemistry, machinery (oils), industrial cleaning, etc.)
• Harmful substance inputs (e.g. water in engine oils, cooling lubricant in subsequent process steps)

Impedance spectroscopy can also be applied to identify properties of substance mixtures, such as:

• Material moisture
• Curing degree of adhesives or building materials
• State of cell emulsions
• Tumour tissue

If you have another application in mind, please feel free to contact us any time.

At Ilmsens, the impedance spectroscopy consists of the following three parts:

1. The ultra-wideband measurement electronics, which are the same for both impedance spectroscopy and near-field radar (e.g. m:explore)
2. Applicator (sensing probe) that interacts with the material that is analysed
3. Data evaluation algorithms
   

Since every application is unique, every process requires different methods of interaction with the measured substance. We discuss the possibilities with our partners and the options include but are not limited to the following specific requirements:

• Size, available space
• Position of implementation
• Form factor
• Robustness

There are fundamentally different setups:

• In-line or bypass setup
• Flow-through or immersion probe

In the impedance spectroscopy, the accuracy of results depends on the following:

• Substances composition
• Complexity of substance compositions
• 
• Frequency range of impedance measurement and
• Quality of analysis software (scope of "learning")

If substance components have distinctive permittivity values (see graphic, values circled in red), they are easy to distinguish and even slight changes in the respective concentrations become apparent. Measurements can demonstrate detectable concentration changes within a few ppm.

If components of a liquid show similar permittivity values, only larger concentration changes become detectable.

In order to illustrate which materials are similar in their electric properties, the following table displays several exemplary materials and their permittivity values based on the indicated sources.

In contrast to some sources, it should be noted that permittivity values are not constant, but rather temperature and frequency dependent. Therefore, the permittivity values in the table can only provide a first indication.
Example: Water (ε_r = 80) and oil (ε_r = ca. 3) can be differentiated very well. Even small concentrations can be easily detected.

Name	εr
Acetone	21.5
Acetic acid	6.2
Ammonia	15.0 … 25.0
Ascorbic acid (vitamin C)	2.1
Gas	2.0
Cotton-seed oil	3.1
Brewer's yeast	25.0
Chloroacetic acid	33.4
Diesel fuel	2.1
Ethanol (ethyl alcohol)	16.2
Fatty acid	1.7
Fish oil	2.6
Hydrochloric acid	5.0
Isopropanol	18.0
Methanol (methyl alkohol)	33.0
Mineral oil	2.0 … 2.5
Palm kernel oil	1.8
Soy-bean oil	2.9 … 3.5
Transformer oil	2.2 … 2.4
Vinegar	24.0 / 37.6
Water (20°C / 120°C)	80.0 / 20.4

The results are partially comparable in the sense that it is possible to recreate laboratory-measured parameters from Ilmsens measurement data.

However, Ilmsens technology should be seen as a complement to laboratory tests and as a useful tool to cover the time between laboratory tests for immediate knowledge about a process.

The advantages of Ilmsens technology are the ability to distinguish substances in-line during the process and to make predictions based on real-time data. This allows a continuous monitoring of processes instead of rare, expensive measurements and allows for immediate recommendations for action.

Our sensors for liquid substances are designed to give information control back to the user.

	Advantages	Disadvantages
Lab	Precision of measured values Off-the-shelf availability Time Resources Cost	Time Resources Cost
Ilmsens	In-line measurement No sample taking Realtime information Ultra-wideband measurement Possibility to recreate conventionally measured parameters from UWB data Inversely, UWB data contain more information than scalar sensors (temperature, pressure, conductivity, etc.) → Additional information about the measured process	Scenario dependent not as accurate as lab measurements

For further information, please refer to our use cases.

The impedance spectroscopy provides accurate and reproducible results under controlled conditions. Deviations of these measurement conditions will result in a more complex data analysis or limitations of the effect that is to be measured. Hence, it should be noted that

• The permittivity depends on external influences, for example temperature or pressure
• The measuring instrument and sample holder should not be subject to temporal fluctuations (drift, contamination, wear)
• There are limits based on the measured substance composition (long-term stability of the measurement setup, complexity of the substance composition, previous knowledge of the composition, cross sensitivities)

Short-range means that objects within a distance of approximately 10 metres to the sensor can be detected. The detection comes from the reflection of the transmitted signal. The distance, velocity (motion) and strength of the reflection of objects is determined by signal delay, Doppler shift and signal amplitude.

Every radar functions according to the fundamental radar principle. This means a radar transmits an electromagnetic wave, which is then reflected as soon as it hits an object with different electromagnetic characteristics than the material the wave is travelling in. The reflected wave can then be received by the radar.

In radar applications the electromagnetic wave is usually transmitted in air. However, it is also possible to transmit through other materials (e.g. concrete).

There is various information that can be obtained from the received signal through simple or advanced data analysis:

• The distance/exact position of an object or specific material parameters can be calculated using the signal propagation time of the received electromagnetic wave.
• The object size, orientation, material and several other object properties can be examined with the reflection strength based on the signal amplitude.
• The speed of the object can be determined by comparing the shape of the received waveform with the transmitted one. The Doppler shift of the electromagnetic wave is evaluated for such purposes.

This information can usually be extracted with little calculation effort.


The minimum and maximum detection distance of a radar depend on the type of radar and antennas used, and the frequency and applicable radio regulations (which limit the transmission power). Short-range means that objects within a distance of approximately 10 metres to the sensor can be detected. The higher the maximum detection range, the lower the detection accuracy in the surrounding area.

The main advantages of radars are:

• Distance, velocity and position is easy to measure accurately with little computing power.
• Differentiating between stationary and moving objects is simple and possible with very little computing power.
• Radars are real-time capable.
• Depending on the used frequency, radars have a very good material penetration (e.g. for materials known as insulators) and can therefore be placed behind covers without degrading the performance. This excludes from this are metallic materials.
• The frequency dependent material penetration can also be used to further investigate detected objects.
• Radars are insensitive to different weather conditions such as rain, fog, snow, dirt or temperature changes.
• Radars do not need optical illumination.
• Even if an object is flat or has an arbitrary form, it is still possible to detect it.

Depending on the application, it may be advantageous to combine the data from multiple sensors (sensor fusion).

In addition to the advantages of radars, Ilmsens' ultra-wideband technology offers:

• Low transmit power
• Harmless to humans, animals and other machines/sensors
• Constantly high measurement rate
• No minimum distance from the sensor to the objects; includes no reduction of the measurement rate close to the sensor
• Low disturbance from rain, fog or dirt due to the wavelengths used
• Detection of dirt on the sensor
• Possibility to position the sensor behind coverings as long as they are not metallic
• No interference with other radars even if they are identically constructed
• Possibility of synchronized multichannel systems and, therefore, reduced computing effort
• 
  

Cameras and ultrasound are widely used technologies, but there are applications where both technologies are insufficient.

• Distance and velocity information can be easily calculated from radar data with little computing effort, while calculating both from a camera image requires a lot of time and computing power.
• Camera and ultrasound both have disadvantages when the optical visibility is poor. Depending on the frequency range used, radar can penetrate material well. Since we are using a frequency range from 6-8,5 GHz, the Ilmsens radar can see through rain, snow, dirt and many other materials, such as plastics, stone, wood or textiles. Only metal is excluded.
• A radar is capable of realtime measurements.Cameras have difficulties determining distance or speed from the images taken. Ultrasound requires more time to boot and measure.
• Material properties can be determined by evaluating the reflection of an object. Due to the wide frequency range used, an ultra-wideband radar – like the one from Ilmsens – can determine more material properties than ultrasound.
• A radar outputs a radargram instead of an image. This makes it possible to protect privacy.

A wide range of applications is possible. The antennas should be installed at an ideal location (which could also be behind any material, except metal), but can also come into contact with the medium being examined. Possible scenarios are, for example:

• Motion detection (high dynamics in the size of the detected objects, e.g. humans or small insects, such as termites)
• Vital data acquisition (contactless and through clothing)
• Moisture determination
• Object detection (for agriculture [e.g. vegetables in the ground], medicine [e.g. carcinoma tissue] or industry)
• Detection of objects or layers inside another material (e.g. concrete)

If you have another application in mind, please do not hesitate to contact us any time.

The Ilmsens short-range radar consists of three parts:

• The sensor itself (e.g. m:explore) depending on the frequency ranged used,
• The antennas fitted to the application
• The data evaluation algorithms

Since every application is unique, the antenna(s) and mounting locations for sensor and antenna(s) must be adapted. We discuss the possibilities with our partners and the options include, but are not limited to the following specific requirements:

• Radiation regulations (regarding the frequency range used)
• Size, available space
• Position of implementation
• Robustness against environmental conditions

Thanks to a high-system stability, high range accuracy of up to 1 µm can be achieved with the Ilmsens short-range radar. However, a high range accuracy does not necessarily lead to high detection accuracy. It is also necessary to consider the range resolution. If two objects are close to each other they still need to be detected as two different objects. The higher the range resolution, the better the differentiation between two objects, and the higher the frequency range used, the better the range resolution. Since the Ilmsens short-range radars are ultrawideband radars they provide a very high range resolution.

In general, measurements from the Ilmsens short-range radar are limited by two factors. On the one hand, the accuracy of the measurement is distance-dependent. So, if small distance changes of an object (such as a heartbeat) are meant to be detected, the object must be close to the antenna. On the other hand, the exact distance depends on the material through which the electromagnetic wave is transmitted. Air is the best material for a high range. Below are a guidelines:

• Distance dependency
  • Up to 2 metres of detection for small movements
  • Up to 10 metres of detection for objects (such as humans)
• 
  
• Material dependency
• • Rising attenuation of the electromagnetic wave with increasing ε_r of the penetrated material
  • Necessary to minimise amount of distortions in the measurment scenarios (Note: Must be adapted individually for each applcation)