Monthly Archives: August 2022

Digital Planar Liquid Flow Sensor

The chemical industry often requires measuring liquid flow in fluidic manifold systems. These often involve high-volume applications but with severe space limitations. For such applications, Sensirion offers a digital planar liquid flow sensor, the LPG10-1000. The sensor uses a planar microfluidic glass substrate that has down-mounted fluidic ports. Measuring only 10 x 10 x 2.35 mm, the LPG10-1000 is a highly compact unit capable of being integrated into any fluidic manifold system.

The sensor combines a digital microsensor and a microfluidic chip to measure the liquid flowing inside the planar glass substrate. The presence of the digital microsensor chip ensures full signal processing functionality. Its digital output is linearized, temperature compensated, and fully calibrated.

LPG10-1000 from Sensirion is an intelligent sensor providing solutions for measuring flow rates from a few microliters per minute to about 1ml per minute. Sensirion has provided a special glass for the wetted material, and it ensures optimum compatibility with the pharmaceutical and biological processes. The low thermal mass of the sensor allows response times lower than 30 ms. The sensor has built-in features for detecting real-time failures like leaks, air bubbles, and clogging.

The Sensirion sensor LPG10-1000 offers several advantages for measuring liquid flow. Its tiny size makes it extremely convenient for integration, even in small spaces. The engineering simplicity of the sensor’s design offers excellent repeatability. The output signal is digital, linearized, and calibrated. Media compatibility is excellent, and chemical resistance is high.

Sensirion has used the media isolated sensing principle for its sensor, as there is no direct sensor contact with the fluid it is measuring. The glass they use is of the inert type, so it is bio-compatible with the chemical process. The sensor offers a digital I2C interface for electronic compatibility.

The LPG10-1000 sensor offers a full-scale flow rate of 1000 microliters, and a sensor output limit of 1500 microliters. The response time for detecting the flow is about 40 ms, with 120 ms from power-up. The operating range for the sensor covers +5 to +50 °C, while the specified temperature range for storage is -40 to +60 °C. The sensor can operate reliably in 0 to 95% humidity and non-condensing conditions. The recommended maximum operating pressure is under 3 bar or 43 psi, and the sensor can withstand a burst pressure of up to 7 bar or 101 psi.

For a full-scale 16-bit output, the digital sampling time of the sensor is 74 ms. However, for a 9-bit output, the sampling time can drop to as low as 1 ms. The sensor operates within a supply voltage range of +3.3 to +3.6 VDC, consuming less than 6 mA operating current.

The internal substrate channel glass material is borosilicate and has a down mount fluidic connection. The introduction of the sensor in a fluidic manifold system causes a pressure drop of only 0.1 millibars at full-scale flow rates. The total internal volume of the sensor is about 11.7 microliters. The cross-sectional flow channel of the sensor measures about 0.9 x 0.9 mm, and the total mass of the sensor is only 0.32 grams.

Cleaning Solar Panels without Water

Most installations of solar panels are in desert areas that provide plentiful amounts of sunshine. While the desert property is cheap, winds are also common. When the wind blows, it carries a huge amount of dust, which forms a layer on the solar panels. Dust on the solar panel reduces their performance, and the electrical output from the panel can reduce by about 30% with only a month of exposure to the elements.

For a 150 MW solar panel installation, even a 1% drop in the output could translate to a loss in yearly revenue to the tune of US$200,000. According to researchers, a reduction of 3 to 4% power output from solar plants all over the world could lead to an annual loss of nearly US$3.3 billion to US$5.5 billion. Therefore, it is essential to keep solar panels clean, and the most common technique presently is by using water.

However, keeping solar panels clean presently requires an annual supply of nearly 10 billion gallons of water. This is enough water necessary for a million people in developing countries. Cleaning solar panels without water is a labor-intensive task, and carries with it the high risk of scratching and damaging the surface of the panels, which also leads to a reduction in the efficiency of the cells.

MIT researchers have come up with an innovative method of cleaning the surface of solar panels. The method does not require the use of water, is contactless, and is automatic.

This innovative new method from MIT uses electrostatic repulsion. This makes the dust particles jump off the panels and does not require water or brushes. When activated, the system runs an electrode just above the surface of the panel. This results in the dust particles acquiring an electrical charge. The solar panels have a transparent conductive layer on top of their glass covering, and this is only a few nanometers thick. The system applies the same electric charge to this transparent conductive layer.

The same charge on the conductive layer and the dust particles makes them repel each other. As the conductive layer cannot move, the dust particles fall off the panel because of the repulsion. The researchers had to change the voltage until they found a range that overcame the adhesion forces and the pull of gravity and allowed the dust to lift away. They then automated the system using guide rails on the sides of the panel and an electric motor.

This is not the first time that engineers have tried to use an electrostatics-based approach to keeping solar panels clean. However, most approaches used electrodynamic screens and interdigitated electrodes. The problem with such screens is they allow ingress of moisture that can damage the electronics. If the atmosphere is dry, and moisture is not an issue, such as on the surface of Mars, the arrangement could be useful. However, on Earth, this can be a serious problem, because even the desert has ample amounts of moisture.

The researchers have found that as long as the humidity is more than 30%, dust removal was easy. However, the process of dust removal got increasingly more difficult with a decrease in humidity. 

High-Performance MEMS Microphone

With the increasing demand for high-quality microphones for consumer devices, the trend is toward MEMS-type microphones that offer high SNR or signal-to-noise ratio and low THD or total harmonic distortion. Apart from this, the microphones must also exhibit a wide dynamic range and a high AOP or acoustic overload point.

The MEMS microphone IM69D130, from Infineon, meets the above requirements superbly. Infineon has designed its microphone to provide low self-noise or high SNR of 69 dB(A), lower than 1% THD at 128 dBSPL, and an AOP of 130 dB SPL.

IM69D130 has a tight sensitivity of 36±1 dB and a phase tolerance of ±2°. With a low-frequency roll-off of 28Hz, the microphone offers a wide dynamic range of 105 dB. The current consumption of the microphone is only 980 µA, while in low-power mode, it consumes only 300 µA.

Infineon has used its patented Dual Backplate MEMS technology for making this microphone. This has given the IM69D130 microphone a miniaturized symmetrical design similar to that of studio condenser microphones. The design offers high linearity of signal output within a wide dynamic range of 105 dB. Even when the sound pressure levels reach 128 dB SPL, the microphone output has a distortion well below 1%. Infineon’s tight manufacturing tolerances result in a flat frequency response reaching as low as 28 Hz and a very close phase matching between microphones. This is a very important factor for applications using multi-microphone arrays.

The electronics associated with the microphone consist of an ASIC along with an amplifier featuring extremely low noise. There is also a high-performing sigma-delta ADC to convert the analog signal from the microphone to a digital signal. The user can select different power modes to suit specific requirements of current consumption.

Infineon trims each IMD69D130 microphone in production with IFX, their advanced calibration algorithm. This not only results in sensitivity tolerances as low as ±1 dB but also matches the phase response tightly to ±2° between microphones. This is very important for applications requiring beamforming support.

Infineon has designed their IMD69D130 microphones as extremely low-latency digital microphones. Their aim for these microphones is to use them in applications that require active noise cancellation, and where the microphone must process the audio data rather quickly.

The IMD69D130 microphones deliver the best-in-class group delay performances. This allows the benefits of digital microphones to system designs that had to rely on analog microphones up until now. The physical size of these microphones is only 4.00 x 3.00 x 1.20 mm.

There are some key benefits of using IMD69D130 microphones. They offer excellent far-field and soft audio signal pick-up. The output signal from these microphones is clear even when the sound pressure levels are very high. Moreover, these microphones enable the precise steering of audio beams for applications requiring advanced audio algorithms.

Typical applications of these digital MEMS microphones include systems with VUI or voice user interfaces such as IoT devices, home automation, and smart speaker systems. Headphones and earphones benefit from the excellent ANC or active noise cancellation offered by these microphones. Conference systems, camcorders, and cameras benefit from the high-quality audio these microphones capture.

MEMS Microphones for Laptops

In the recent pandemic, people took to virtual meetings using their computers and laptops. However, most often, the substandard quality of the audio led to an unsatisfactory experience. That’s because people’s expectation of consumer devices has increased significantly. They want to make high-quality calls from wherever they may be. They could be on the street, in an open office, or in a crowd.

People expect their devices to have ANC or active noise cancellation, transparent hearing, and voice control. However, these require more sophisticated and better microphones.

For instance, people engaged in video conferencing, want their experience to be as close as possible to a real, face-to-face meeting. Now this depends, to a great extent, on the audio quality, and people expect high-quality audio without having to put on additional devices, such as headphones.

Achieving good quality audio requires the application to use a combination of high-quality hardware and software. It is necessary to have algorithms that provide good noise reduction, reverberation reduction, enhanced beamforming, and good direction of arrival detection. These are essential for high-fidelity transmission and audio recording in a wide variety of conditions and situations. However, the quality of the entire chain is dependent on the primary sensor, the microphone.

Most good-quality microphones that have been around for a long time tend to be large and expensive, and primarily confined to audio recording studios. However, consumer equipment typically requires microphones that are mass-produced with tight manufacturing tolerances, and physically small. MEMS microphones suit these requirements very well.

For a microphone to be qualitatively described as good, it must possess some performance characteristics. The first among them is the SNR or signal-to-noise ratio. SNR of a microphone is the difference in its output between a standard reference signal input and the microphone’s self-noise. All elements of a microphone contribute to its self-noise. This includes the MEMS sensor, package, ASIC, and the sound ports.

SNR is important when the microphone is detecting sounds or voices that are at a distance from it. This is because the input signal decreases with distance, as sound level halves at twice the distance. Further, signal losses can come from the system design, room conditions, and sound channel. A good microphone with a large SNR can capture sound even at large distances. This helps with capturing input signals for algorithms, voice commands, and recording.

The next important characteristic of a good microphone is its THD or total harmonic distortion. This refers to the presence of harmonics in the microphone’s output that are not present in the input signal. The point where the THD reaches 10% is important as this represents AOP or acoustic overload point. At this point, the output from the microphone contains clipping and other noises, because the signal is too loud for the microphone.

The latest MEMS technology allows building of studio-level microphones for consumer devices like laptops. This has been aptly demonstrated by Infineon using their XENSIV IM69D127 and IM73A135 MEMS microphones that are allowing OEMs to build laptops with the next level of audio quality.

Heat Spreading for Thermal Management

Proper thermal management is necessary for ensuring the performance and reliability of electronic devices. Conceptually, this is simple, starting with the transferring of unwanted heat from the source to a larger area for effective cooling by dissipation. However, an implementation may be a difficult task.

Devices that generate heat generally have surfaces that are not large enough or smooth enough. Therefore, they cannot efficiently transfer heat as their thermal impedance is not adequately low. Some devices may not have a planar surface, thereby increasing the challenge of thermal management. Moreover, the challenge can increase with the position of the component to be cooled. If the location of the hot component is deep within the system, extracting the potentially damaging heat may become further complicated.

Many applications depend on thermal greases and pastes for improving thermal conductivity. However, this can be tricky, especially as the coverage may be insufficient, and over-application may result in spillage onto circuit board traces causing short circuits. Another limitation is thermal greases and pastes can only move the heat perpendicular to the surface, and not laterally from the source.

Therefore, designers are now replacing thermal greases and pastes with a variety of TIMs or Thermal Interface Materials. These include fillers and heat spreaders for providing low thermal impedance. This is necessary for the effective transfer of heat while removing any concerns about PCB surface contamination.

TIMs can also meet specific system needs, as their structural design can allow the transfer of heat perpendicularly or laterally. Moreover, TIMs are available in a variety of thicknesses. This enables designers to match them to the requirement of specific applications. They can provide good reliability as they are mechanically stable at elevated temperatures, and they provide high electrical isolation. Furthermore, they are easy to apply.

Placing TIMs between the source of heat and a cooling assembly helps to improve the heat flow through better thermal coupling. Here, two factors improve the efficiency of the thermal coupling. First, TIMs have the ability to conform to surface irregularities. This eliminates pockets of insulating air that actually reduce the thermal conductivity of the interface. Second, TIMs have a high thermal conductivity that is necessary to effectively move heat from the source to the cooling assembly.

Würth Electronik offers TIM (blue) for filling in microscopic irregularities. These irregularities exist on the surfaces of components and cooling assemblies, reducing thermal coupling.

Apart from thermal conductivity, there are other concerns for selecting a specific TIM. One of them is the operating temperature—TIMs are available for different temperature ranges. Another is the distance between the mating surfaces.

Other concerns are whether the TIM needs compression for delivering the optimal amount of thermal transfer and whether the TIM has the withstanding capability for the compression pressure it will face. Würth Electronik offers TIMs with adhesive on one surface that enables mechanical fixing. TIMs may also have to provide electrical isolation.

TIMs made of synthetic graphite offer very high thermal conductivity. The WE-TGS family from Würth Electronik is a synthetic graphite heat spreader. It measures 297 x 210 mm and has a thermal conductivity of 1800 W/mK.

Challenges of Low Power Applications

Designing for ultra-low-power electronics requires a trading-off between higher performance against longer battery life. Although battery capacities have improved substantially, the fundamental challenge remains the same as that of achieving higher performance for longer periods.

Reducing the power consumption and managing battery life depends primarily on minimizing the quiescent current of a circuit. This is best explained with the help of a sensor node in the Internet-of-Things. For instance, a low-power IoT application may have a battery-powered MCU controlling the door lock via a Wi-Fi connection or Bluetooth.

As most of these types of systems spend a major part of their operating time in standby mode, the quiescent current consumption in standby or sleep mode is the limiting factor when considering battery life. Careful optimization of power-management blocks of low quiescent current can lead to extending the battery life from a low of two years to a high of five or more years.

The most important bottleneck is in achieving low no-load quiescent current for low-power systems with the duty-cycle operation, as this enables longer battery life. However, designers must tradeoff between output power range, die-package area, and transient noise performance. One must realize that reducing quiescent current by decades without sacrificing performance or area can only come about through reexamining both circuit techniques and silicon technologies.

Standby quiescent current has been a concern. Historically, most solutions limited themselves to a narrow set of low-power systems. However, there have been recent breakthroughs in a quiescent current reduction in power-management building blocks. Now, LDOs or low-dropout regulators and supervisors, power switches, and DC/DC converters are using these blocks for end equipment. These include personal wearables, automotive sensors, and industrial meter applications.

For instance, the quiescent current in 5V LDOs has approximately come down by 90% every three years over the past decade. Not only has the quiescent current reduced, but there have been circuit improvements and optimization of process technologies that have led to the reduction of die area while improving the transient-noise performance.

So, what constitutes quiescent current? Basically, this is the amount of current drawn when the circuit is in an enabled condition but not supporting an external load, and not switching. This is different from the shutdown current, which the device draws from the power supply when it is in a disabled condition.

Power regulators are mostly always-on functions, and their quiescent current contributes to the overall system quiescent current. Within the power regulator, all voltage references, error amplifiers, output voltage dividers, and protection circuits contribute to the overall operating currents.

Therefore, designers determine the quiescent current that a device draws from a battery or power source by taking into account the always-on functions and leakage sources from inductors, capacitors, and resistors.

On the other hand, switching converters are different. Most switching converters include a power-saving mode. This enables a longer period for non-switching times, resulting in a reduction of the average quiescent current. But most low-quiescent current devices have internal parasitic capacitors. These cause a longer response time as they must change to the new operating point.


A solid-state Lidar chip works by emitting laser light from an optical antenna. A tiny switch turns the antenna on and off. The light reflects off the sample and the same antenna captures it. For 3D imaging, the Lidar chip has an array of such antennae. The switches sequentially turn them on in the array.

An array of MEMS switches for high-resolution solid-state Lidar can reduce its cost significantly. This allows the solid-state Lidar to match other inexpensive chip-based radar and camera systems. This removes the major barrier to the adoption of Lidar for autonomous vehicles.

At present, autonomous highway driving and collision avoidance systems use inexpensive chip-based radar and cameras as their mainstream building blocks. At the same time, Lidar navigation systems, being mechanical devices and unwieldy, are also expensive, costing thousands of dollars.

However, researchers at the University of California, Berkeley, are working on a new type of high-resolution Lidar chip and this may be the game-changer. The new Lidar uses an FPSA or Focal Plane Switch Array. This is a matrix of micron-scale antennas made of semiconductors. Just like the sensors in digital cameras do, these antennas also gather light. While smartphone cameras have impressive resolutions of millions of pixels, FPSA on the new Lidar has a resolution of only 16,384 pixels. However, this is substantially larger than the 512 pixels that the current FPSA has.

Another advantage of the new FPSA is its design is scalable. Using the same CMOS or Complementary Metal-Oxide Semiconductor technology that produces computer processors, it is possible to reach megapixel sizes easily. According to the researchers, this can lead to a new generation of 3D sensors that are not only immensely powerful but also low-cost. Such powerful 3D sensors will be of great use in smartphones, robots, drones, and autonomous cars.

Surprisingly, the new Lidar system works the same way as mechanical Lidar systems do.  Mechanical Lidars also use lasers for visualizing objects situated several hundreds of yards away, even when they are in the dark. They also generate high-resolution 3D maps for the artificial intelligence in a vehicle for distinguishing between obstacles like pedestrians, bicycles, and other vehicles. But for over a decade, researchers have tried to put these capabilities on a chip, without success, up until now.

The idea is to illuminate a large area. However, the larger the area illuminated, the weaker is the light intensity. This does not allow reaching a reasonable distance. Therefore, researchers had to make a trade-off for maintaining the light intensity. They had to reduce the area that their laser light was illuminating.

The new Lidar has an FPSA matrix consisting of tiny optical transmitters. Each transmitter has a MEMS switch that can rapidly turn on and off. This allows time for the waveguides to move from one position to another while allowing channeling the entire laser power through a single antenna at any time.

Routing light in communications networks commonly uses MEMS switches. The researchers have used this technology for the first time for Lidar. Compared to the thermo-optic switches that the mechanical Lidar uses, the MEMs switches have the advantage of being much smaller, consuming far less power, operating faster, and performing with significantly lower light losses.

Encoders for Autonomous Mobile Robots

Whether it is AMR or autonomous mobile robots, AGC or automated guided carts, AGV or automated guided vehicles, various types of robots or robotics are increasingly important to the industry. They use these robots to move parts and materials from one place to another in every environment. For instance, goods move from manufacturing to warehouse, and thence to grocery stores to face customers.

It is important that these automated machines work correctly because precision is a vital requirement. This requires reliable motion feedback to the controllers. This is where encoders come in. For instance, autonomous motion applications requiring motion feedback are useful in steering assembly, drive motors, lift controls, and more.

The industry uses several automated carts and vehicles. They use them for lifting products and materials onto and from shelves and floors in warehouses and other storage areas. To do that reliably and repeatedly, these machines require accurate and precise motion feedback. This ensures that materials and products reach where they need to go, without incurring damages.

The Encoder Product Company offers to draw wire solutions, and encoders with rack-and-pinion gears provide reliable motion feedback. This ensures all lifts stop at the right locations, thereby moving materials and products safely to their destinations. Their motion feedback options for lift control involve Model LCX, for high performance with absolute feedback option, and Model TR2, a rack-and-pinion gear as an all-in-one unit.

The Model LCX135 is one of a draw wire series, providing an excellent solution for the control of lifts. Internally, incremental and absolute encoders provide excellent lift control feedback using the CANopen communication protocol.

Automated carts and vehicles require drive motor feedback. As they move around facilities like warehouses, the controller in these vehicles needs reliable motion feedback to ensure the motors are in the proper transit areas/corridors designated for them. The motion feedback also ensures they stop and start accurately.

Motion feedback devices from the Encoder Product Company provide this reliable, repeatable motion feedback. Their Model 15T/H is a compact and high-performance encoder. It is available in the blind-hollow bore or thru-bore designs. The Model 260 is a more economical and compact encoder with a large thru-bore design. The next model 25T/H is a high-performance 2.5” encoder. While Models 25T and 260 are incremental encoders, absolute encoders are also available, and they use the same CANopen communication protocol.

To ensure the correct drive path ad steering angle, the steering assembly also needs to provide precision feedback. Absolute encoders provide the best way to ensure proper motion feedback for these steering assemblies. This is because with absolute encoders it is possible to ensure smart positioning while providing the exact location while in a 360-degree rotation.

The Encoder Product Company offers several absolute encoders. Among them is the Model A36HB, a compact absolute encoder with a 36 mm blind hollow bore. Another is the Model A58HB, an absolute encoder with a 58 mm blind hollow bore.

Where safety is considered paramount, the Encoder Product Company offers redundant encoders. These are simple solutions and economical also. Using redundant encoders allows the application to rely on different technologies, ensuring at least one encoder will continue to function even when the other has failed.

Passive and Active Thermal Management

Keeping electronics cool is an important goal for designers, and they have a wide variety of options with active and passive thermal management. With power densities continuing to increase, and microprocessors drawing more power for meeting the demands of computational and functional requirements made by high-powered applications, thermal management is, even more, a requirement.

Today, densely populated circuit boards use high-power components to create systems that generate more heat than ever before. Therefore, designers face an upward challenge in implementing effective thermal design and management, as heat is the major cause of electronic failure.

The operational life and functionality of components can be compromised severely when the application exposes them to high localized temperatures, or when they operate at excessive temperatures. Prolonged operation in these extreme conditions can also lead to degradation of the components and ultimately, failure.

Designers ensure reliability and proper performance by arranging to transport the excess heat away from system hot spots and critical components. By dissipating this heat to the ambient environment, they manage to keep the system temperature within acceptable limits. Thermodynamics offers three basic methods of heat transfer that designers use to their advantage. They derive the thermal solutions from the basic principles of conduction, convection, and radiation.

Conduction allows heat to flow from an area of higher temperature to one with a lower temperature, provided both are within a single medium, which can be a solid, liquid, or gas. The process of conduction attempts to equalize thermal differences. The process also transfers heat between media in direct physical contact, such as between two touching solids.

Convection is the process of transfer of heat between a solid body and a fluid, which can be liquid or gas. The bulk motion of the fluid helps in the heat transfer. During the natural convection process, cold ambient air assimilates heat from any heated surface nearby. The air becomes warmer and, therefore, less dense, causing it to rise and creating low pressure. Cooler air from the surrounding areas rushes in to balance the low pressure created by the rising warm air, which, in turn, rises when it warms up. This creates a natural cycle of airflow, removing the heat.

In the process of radiation, a hot body radiates thermal energy as electromagnetic waves. The surface condition of the radiating surface and its temperature determines the amount of emission. Likewise, a cold body can absorb electromagnetic waves, and the amount it can absorb depends on its surface condition, its temperature, and the temperature of the surrounding environment.

All the above are examples of passive thermal management. These are commonly in use as they are easy to implement and are the least expensive. In some situations, however, passive thermal management is not adequate for removing excess heat. These situations call for active thermal management, such as using a fan to force an air-flow movement over the heated surface. Controlling the airflow may require a change in the fan size and its configuration. Optimization of the flow path may require proper placement of the fan and its orientation.