# What are Capacitive Accelerometers?

In the electronic industry, there are various applications requiring accelerometers. For instance, the automotive industry uses accelerometers to activate airbag systems. Cameras use accelerometers to actively stabilize pictures. Computer hard disk drives rely on accelerometers to detect imminent external shocks that may damage the device—the accelerometer protects the device when an external shock is imminent. But, these are only a few applications for accelerometers.

In reality, there are endless possibilities for accelerometers uses. Microfabrication technologies have advanced steadily to enable the low-cost, tiny micro-machined accelerometers that the industry uses today. In fact, the small form and low cost are the two main factors allowing the application of these devices to cover such a broad spectrum.

The most common method of measuring acceleration is using a mass-spring-damper structure, converting the acceleration to a displacement quantity. Applying the capacitive sensing technique makes it easy to convert this displacement to an electrical signal proportional to the applied acceleration.

For the mass-spring-damper structure, a known quantity of mass, also known as test mass or proof mass, connects to the sensor frame through a spring. When the sensor frame senses acceleration because of an external force, the proof mass tends to hang back due to its inertia. This allows the relative position of the proof mass to change with respect to the sensor frame.

An external observer sees the proof mass being displaced to one side of its resting position. At the same time, the displacement of the proof mass compresses or elongates the spring. This exerts a force proportional to the displacement on the proof mass. The force from the compressed or elongated spring pushes or pulls the proof mass to the other side and makes it accelerate in the direction of the external force.

If the designer has chosen appropriate values for the various parameters in the system, the displacement of the proof mass will be proportionate to the value of the frame acceleration, once the transient response of the system subsides.

In summary, a mass-spring-damper structure converts the sensor frame acceleration to a displacement of the proof mass. Now the question is, how to measure this displacement? Although there are several methods of measuring this displacement, one of the most common arrangements is the capacitive sensing technique.

Fixing two electrodes to the sensor frame and a movable electrode to the proof mass creates two capacitors. As the proof mass moves, the capacitance between the moving electrode and that of one fixed electrode decreases, while the capacitance between the others increases. By measuring the change in the sense capacitors, it is possible to detect the displacement of the proof mass. This is then proportional to the input acceleration.

To measure changes in the sense capacitors accurately, it is necessary to apply the technique of synchronous demodulation. It is easy to do this while employing the signal conditioning offered by the ADXL family of accelerometers from Analog Devices. These devices use a 1 MHz square wave as the AC excitation for the sense capacitors.

As the movable electrode moves close to one of the fixed electrodes, the amplifier input bridge receives a larger proportion of the excitation voltage from the moving electrode. If the movable electrode is at rest, the voltage at the amplifier input is zero.

# Ultra-Low Pressure Sensors with High Accuracy

Board-mounted ultra-low pressure sensors are in great demand. Especially as they provide extremely high accuracy, as necessary for diverse designs like medical ventilators. Variable air volume control systems also need them for the conservation of building energy. These pressure sensors are useful for addressing problems that engineers face with limited space and reliability. Board-mounted ultra-low pressure sensors with high accuracy are available to measure differential, gauge, and absolute pressure.

Board-mountable pressure sensors are popular as it is possible to mount them on printed circuit boards, allowing direct integration into an electronic assembly. Being compact, their low footprint addresses space constraints. In addition, their microstructure is highly sensitive to the differential, gage, and absolute pressure changes. This enables the electronics to acquire accurate, ultra-low pressure readings.

Several medical applications require ultra-low pressure readings with high accuracy. Some of these medical applications include medical chemistry, sleep apnea machines, anesthesia machines, ventilators, and hemodialysis machines. For instance, the hemodialysis machine depends on such pressure sensors for regulating the pressure in their mixing tanks. This is necessary as blood reaches the artificial kidney, and then it needs regulation to and from the patient.

When used in ventilators, the ultra-low pressure sensors aid in monitoring the breathing of the patient, while detecting if there is a sudden deterioration due to a clogged filter. Anesthesia machines use high-accuracy pressure sensors to measure the pressure of oxygen and air and ensure it never exceeds the safe level, both to and from the patient.

Ultra-low pressure sensors in sleep apnea machines monitor the pressure of air delivery to the patient. It is also possible to monitor blood pressure and hospital room air pressure. Anesthesia equipment and ventilators also use these board-mounted, high-accuracy, low-pressure pressure sensors.

Chemistry analyzers in medical chemistry also use these high-accuracy pressure sensors. For instance, they help with pipettes in drawing the proper amount of fluids, detecting displacement of vials, checking if the air is not being drawn in, and recognizing the presence of obstructions. Additionally, they are useful in applications like automated laboratory testing equipment, molecular testing, and flow cytometry.

Energy conservation in buildings also requires high-accuracy, ultra-low pressure sensors for monitoring the pressure in filters and optimizing it when they are replaced. They are also helpful in determining if the filter is missing or clogged. These high-accuracy sensors are sensitive enough to determine the change in room pressure if a window is opened. They can automate the change necessary in airflow to accommodate adjustments in window positions.

Variable air volume or VAV systems can integrate these sensors to ensure a balanced airflow throughout the building. Flow calibrators, gas flow instrumentation, barometry, chromatography, and pneumatic controls also use them among many others.

Selecting a suitable board-mounted sensor requires making design choices involving the environmental temperature, operating pressure range, and media type, among others. However, there are other considerations also when selecting a board-mounted, high-accuracy, ultra-low pressure sensor. These include pressure range and burst pressures, accuracy, total error band, stability, energy efficiency, and moisture sensitivity levels.

# Radar Sensors for Smart Homes Enable Energy Efficiency

With the increase in the application of smart homes, the number of connected devices is also growing. Although this is making the lives of users more convenient, it is also resulting in an increase in energy consumption. This is due to the devices being either permanently active or in standby mode, ready for use at all times, even when there is no one home. Now Infineon is offering their radar sensor, the XENSIV, to make smart homes become more energy-efficient.

By an estimate, at present, there are more than 200 million smart homes around the world. This number is forecast to exceed 500 million by the end of a few years in the future.

The use of digital devices with increasingly ingenious functionalities helps to make houses smarter. However, there is a flip side to this—the increase in energy consumption—despite most modern devices showing a trend of steadily decreasing standby power consumption. This is because most smart devices need power even when they are in standby mode, to be capable of reacting instantaneously to user input. On many occasions, it is not at all necessary for a device to run in standby mode, consuming energy, primarily when there is no one present.

The radar sensor from Infineon aims to solve this issue while meeting the requirements of both digitization and energy efficiency. Capable of operating in almost all smart home systems, radar sensors are highly sensitive devices. They can detect the presence of a person and whether a device needs to be ready. This action is similar to that of the screensaver that kicks-in in on the monitor of a personal computer, when there is no activity from the mouse or keyboard after a certain time but reactivates the monitor as soon as the mouse or keyboard detects a new input. The truly smart and energy-saving device from Infineon, operating at 60 GHz, performs a reliable detection of the absence or presence of a human.

Devices like smart speakers, thermostats, and digital assistants consume very little power when in their normal standby mode. However, their energy consumption can reduce still further if they are forced into a deep sleep mode, especially when no one is around. Doing this can save a few more watts of power.

Other devices like a TV, laptop, sound system, or the air-conditioner can consume several 100 Watts when they are on. Switching them off when no one is likely to use them soon, such as when no one is present at home, can therefore save a lot of energy.

The radar-based smart device continuously checks to sense if there is anyone present or is moving about. If it detects there is no one present, it can switch other devices to a deep-sleep mode or switch them off entirely, thereby helping to save energy. The radar module consumes only about 0.1 W, and this is significantly lower than the energy demands of many other devices, even when they are in their standby mode.

# Handling Grippers

Material handling in industries is increasingly relying on grippers. Industries, ranging from automotive assembly to electronics manufacturing, all handle their materials with grippers. The increasing requirement for grippers is evident from the market being worth \$100 million in North America alone today, with the number expectedly growing by 5% annually.

The sudden spurt in growth in the use of grippers can be attributed to the rise in robotics. This includes industrial robots taking on special tasks like handling increasingly complex workpieces. Designers now can take their pick from more types of grippers than before. However, even with the latest developments in robotics and gripper technology, picking the most suitable gripper for a specific application can be a daunting task.

The market today has a plethora of grippers including mechanical, adaptive, soft, magnetic, and vacuum types, with each type offering key design features and benefits. For instance, adaptive and soft grippers adapt themselves to the contours of the workpiece and are useful in various handling applications.

Mechanical grippers, both electric and pneumatic types, are popular for handling applications. Of these, the pneumatic types make up about 90% of the demand, as these tend to be lighter and more cost-effective compared to the electrical types. Being more suitable for harsh environments, pneumatic grippers have faster cycle rates and higher grip forces.

On the other hand, electric grippers offer their users better travel and force control along with greater precision. However, the presence of motors and other internal components in these grippers tends to make them heavier and increases their upfront costs.

Irrespective of being pneumatically or electrically operated, there are several design classes of mechanical grippers. For instance, parallel grippers have fingers that can pull directly apart. The most common among these is the two-finger parallel gripper. These make up more than 85% of the market for mechanical grippers. Another version is the three-finger gripper, and it can perform centering functions and handle round objects.

Other classes of mechanical grippers include the angular and radial versions. These typically have fingers that open at an angle. For instance, angular grippers open their fingers only to 30-degrees, while radial grippers can open their fingers up to 180-degrees, allowing them to handle workpieces of varying dimensions while being slower than angular grippers.

Selecting grippers for a specific application requires considering important factors. Depending on the nature of the workpiece, the designer must consider the gripping force required, the guiding strength of the jaw, and the type of the gripper itself. For instance, long gripper fingers require a long lever arm to exert greater torque on the jaws. There are flat finger designs that offer a friction-based grip for durable and bulky parts. On the other hand, handling slippery parts that require precision placement must use encapsulated designs.

Encapsulated designs have fingers with a profile shape matching the object they will handle. Usually, the fingers will be curved to hold a round object. This helps to retain the object in a specific position while preventing that part from dropping if the pressure is lost.

# What is Ambient Sensing?

Although smart homes have been around for several years now, this industry is rather nascent. Even though we are familiar with the use of Amazon Alexas and Google Homes as smart devices, but for smart homes, they have their limitations.

Smart devices do use technologies promising levels of interoperability and convenience that were unheard of a few years ago. However, they have not been able to fulfill current expectations. For instance, they struggle if there is no home network, cannot use unprocessed data, and are typically standalone devices.

Movies provide a better concept of a smart home. They present a futuristic building with levels of autonomy and comfort far beyond what the current technology can provide. In the real world, our ability to interact with them is rather limited.

For instance, the smart technology available at present allows interaction with voice commands only, thereby limiting their autonomy. Although the current technology boasts of voice recognition, this is still frustrating and cumbersome to use. Most people seek a seamless experience that comes with higher intuitive or human interaction.

For instance, it is still not possible to unlock a smart home simply by improving voice commands. Although audio sensors do form a crucial element for intuitive interaction with a smart home, making them a part of a sensor array for providing better contextual information would be a better idea. For genuinely smart home, the devices must provide a more meaningful interaction, including superior personalization for contextualized decision-making.

While it may be possible for manufacturers to pack in unique sensor arrays in devices, some sensor types could prove to be more useful. For instance, cameras provide huge amounts of information, and smart systems could make use of this fact to perceive the smart home in a better way. Adding acoustic sensors, and gas sensors along with 3-D mapping could be one way of bringing smart environments to the next level.

By collating these inputs, smart devices can understand and implement individual preferences better. For instance, depending on who has entered or exited the room, a smart device can change the sounds, lights, safety features, and temperature matching that person’s profile. Smart devices must not limit themselves to comprehending the ambient alone, but be capable of changing the environment, even without direct inputs.

These features could go beyond providing comfort alone. For instance, with motion sensors, the device could extend security. Along with motion sensing, individual recognition, and 3-D mapping could make homes much safer. For saving energy, sensors for presence, daylight sensing, and temperature measurements could dim lights or adjust air conditioning for better comfort on hot days.

One of the issues holding back such implementation is consumer privacy. While homeowners have grown accustomed to smart speakers, endless examples are available of data-mining organizations that observe the consumer’s daily interaction with these devices. For instance, Amazon’s Astro robot has been accused of data harvesting and there is criticism of Facebook’s smart glasses by the Data Privacy Commission in Ireland. As devices get smarter and use more ambient technology, consumers will have to share greater amounts of data than they are doing at present.

# What are Axial Flux Motors?

AC induction motors are no doubt the most popular and widely used electric motors today. For DC applications, there are permanent magnet motors. However, newer applications are demanding different types of motors with higher efficiency and better speed-torque characteristics. One such application is the electric vehicle sector, where axial flux motors are gaining traction.

Axial flux motors are not new. For the past few decades, manufacturers have been using these motors for stationary applications like agricultural machinery and elevators. With modifications and innovations over the past decades, axial flux motors are now capable of running airport pods, electric motorcycles, delivery trucks, aircraft, and electric cars.

Induction motors and permanent magnet motors are most often known as radial flux motors, as the flux they generate radiates out perpendicularly, relative to their axle. With extensive development, engineers are aiming to optimize the weight and cost of radial flux motors, but the going has been asymptotic. Therefore, moving to a completely different type of machine like an axial flux makes better sense.

With the axial flux design, a permanent magnet motor can provide higher torque for a given volume than a similar motor of radial flux design can. This is because the axial flux design works with a much larger active magnetic surface area to generate torque rather than the motor’s outside diameter.

Therefore, the axial flux motor can be much more compact, with an axial length far shorter than that of their radial counterparts. Because of their shorter axial length, axial flux motors are more suitable for applications that use a motor inside the wheel. Although these motors are slim and lightweight, they can provide the machine where they are mounted with higher power and torque density than a comparable radial motor can, without resorting to high-speed rotation.

The shorter, single-dimensional flux path also provides the axial flux motors with high efficiency, typically over 96%. This is a tall order for the best 2D radial flux motors available on the market.

Compared to radial flux motors, axial flux motors can be five to eight times shorter, and two to times lighter. Both these factors improve the options for designers of EV platforms.

Axial flux motors are available in two principal technologies—dual-rotor, single stator, and single rotor, dual stator.

In a permanent magnet motor using radial flux technology, the magnetic flux loop starts from a permanent magnet on the rotor. It then passes through the first tooth of the stator, continues to flow radially along the stator, and passes through a second tooth, arriving at the second magnet in the rotor.

In an axial flux motor, using the dual rotor technology, the flux loop begins at the first magnet. It then passes axially through the stator tooth arriving immediately at the second magnet. Therefore, the flux has to travel a much shorter distance compared to that in the radial flux motor. This allows the axial flux motor to be much smaller for the same power, increasing its power density and efficiency. In contrast, the flux has to follow a 2-dimensional path inside a radial flux motor.

# How to Effectively Mount Accelerometers

An appropriate coupling between the accelerometer and the system it is monitoring is essential for accurate measurements. Engineers use different methods for mounting MEMS accelerometers, and this affects their frequency response.

The resonance of the mounting fixture plays an important role, as it can introduce an error in the measurement. Accelerometers using MEMS sensors typically use a printed circuit board or PCB for mounting the sensor, and there may also be other mechanical interfaces between the PCB and the surface of the object it is monitoring. This creates a mechanical system that can have multiple resonances within the frequency range of interest.

For instance, the resonant frequency of the mounting structure may be close to the frequency of the acceleration signal. This will cause the sensor to receive an amplified signal in place of the original acceleration.

Again, if the mechanical coupling causes damping, the sensor will likely receive an attenuated signal.

That means, unless applying proper mounting techniques, it is not possible to take full advantage of the accelerometer’s bandwidth. This is especially so when the measuring acceleration signals are above 1 kHz. Engineers apply three types of accelerometer-mounting techniques such as stud, adhesive, and magnetic mountings.

Stud mounting requires drilling a hole in the object and fixing the sensor to the device under test with a nut and a bolt or a screw. This method of mounting provides an immobile mechanical connection. But it is capable of effectively transferring vibrations of high frequencies from the object to the sensor.

Proper stud mounting requires the coupling surfaces to be as clean and flat as possible. Using a thin film of some type of coupling fluid like oil or grease between the coupling surfaces aids in improving the coupling. The fluid fills small voids between the surfaces, thereby improving transmissivity. It also helps to use a torque wrench to tighten the stud to the manufacturer’s specifications.

Where it is not possible to drill a hole in the device, engineers use an adhesive to couple the sensor to the object it has to monitor. Depending on the nature of the object, engineers use glue, epoxy, or even wax for the coupling. They select the adhesive depending on whether the mounting is temporary or permanent. In case the surface of the object is not smooth, engineers sometimes use an adhesive mounting pad or mounting base. While adhesives fix the mounting pad to the test surface, a stud mounting fixes the sensor to the mounting base.

Engineers have an alternative method of fixing accelerometers, that is, by using magnetics. However, this method is only suitable for ferromagnetic surfaces. If the surface is non-magnetic metal or very rough, engineers often weld a ferromagnetic pad to it to act as a magnetic base.

As the stud mounting method offers a relatively firm connection as compared to the adhesive and magnetic methods, it is suitable for higher frequency signals for measuring acceleration. The adhesive and magnetic methods of mounting accelerometers are suitable for applications where the acceleration signals are below a few kilohertz.

# Reducing Downtime with Remote Alarm Systems

Converting an automated plant to a smart factory is definitely a leap forward. However, it requires enabling a flexible and fully connected system to learn and adapt to new requirements, using a steady stream of data coming from production systems and connected equipment.

Nowadays, there is a convergence of extreme challenges facing manufacturing plants. Most consist of an aging workforce with issues of knowledge transfer, there is increasing demand for high-quality products, the need to use fewer resources, coupled with pandemic situations like that from COVID-19. Not only must these issues be navigated, but manufacturing plants must also maintain ongoing operations while controlling costs. Additional situations like unplanned downtimes can often cause financial disasters and logistical nightmares.

However, there is a silver lining to this dark cloud. IIoT, coupled with machine connectivity and monitoring solutions, is providing solutions for mitigating the above-unexpected problems including challenges of staffing.

A report from Deloitte and the Manufacturing Institute had forecasted an expected shortage of 2 million workers for US manufacturing during 2015-2025. The pandemic has only exacerbated the situation. In their latest report, Deloitte and the Manufacturing Institute claim that by 2030, roughly 2.1 million manufacturing jobs will remain unfulfilled. According to the report, this will cost the US economy about \$1 trillion by 2030.

Manufacturing plants spend millions of dollars each year as capital for improving equipment and facilities to protect employees, increase product safety, and reduce costs. This is very important, as equipment may run from 16-20 hours a day, every day, 24/7, especially in food processing plants. Downtime primarily is from equipment failure, causing an astounding \$30,000 per hour in these food processing facilities.

This is where the iFIX SCADA system along with the WIN-911 Advanced remote alarm modification software from GE can help ensure the plant continues to operate non-stop.

One of the main ideas is having a sensor monitoring if the machine is working properly, rather than having someone crawl under it to check it out. The other is to use a remote alarm monitoring notification software, allowing fewer people to monitor far more assets with devices they already have—smartphones and tablets. For continuous monitoring of systems, uninterrupted remote availability is essential. The advantage of the system is staff need not remain onsite, and the facility needs fewer people.

Earlier, remote monitoring involved emails, texts, and phone calls. However, monitoring critical plant systems now extend beyond these. They include apps featuring time-saving tools like team chats, real-time alarm acknowledgments for troubleshooting, and resolving plant problems. They also provide detailed reporting so that future incidents do not occur. While this leads to fewer emergency shutdowns, it also requires fewer resources and lower spending on maintenance and overtime.

The mobile alarm notification app is software integrating seamlessly with the HMI or SCADA software of an industrial operation. This allows employees to monitor, receive and acknowledge alarms from machines and plants on smartphones and tablets. This way they can remain free to work from any remote location such as their homes.