Category Archives: Sensors

What are Linear Image Sensors?

Fairchild Imaging makes CMOS 1421, a linear image sensor. This is an imaging device with a wide dynamic range of 94 dB or 52000:1, with excellent linearity. The device is a linear sensor, meaning it has 2048 x 1 high-resolution imaging sensors. Fairchild has designed this linear sensor for medical and scientific line scan applications such as optical inspection or fluorescent imaging that require wide dynamic range, high sensitivity, and low noise operation.

With several acquisition modes, this photodiode pixel has an optical area measuring 7 x 10 µm with a pitch of 7 µm and a fill factor of 85%, making the operation of this sensor very flexible:

  • Read after Integration: This mode is ideal for applications with high quality signals
  • Buffered Read after Integration: is a high speed mode that integrates the next line while reading the current line
  • Read on Integration: This is a non-CDS mode, allowing the highest speed of operation
  • Multiple Read during Integration: This mode is for low-light applications, permitting oversampling during integration

Other than the above, a programmed mode, accessible through JTAG interface, meets a wide range of specialized imaging requirements. Readout cycles in this mode are controllable through external signals.

CMOS 1421 has several features such as very low dark current, very low readout noise, and non-destructive readout for fowler sampling. Along with anti-blooming drain and electronic shutter, the CMOS 1421 also features two independent gain settings for each pixel. The entire device is enclosed in an RoHS compliant CLCC and PLCC package of 22.35 x 6.35 x 2.85 mm dimensions. The device consumes 40 mW of power while operating from 3.3 VDC. Major applications of linear image sensors are in microscopy, photon counting, and fluorescent imaging.

CMOS 1421 has a pixel array consisting of a photodiode, a pixel amplifier, and a sample and hold circuit. Along with the above, each pixel has a noise suppression circuitry and a gain register. While the pixel-level gain affects the device sensitivity, it also has a bearing on the noise and conversion factor of the sensor.

Linear image sensors from Fairchild use thinned back-illuminated large area arrays. Fairchild offers custom capabilities such as extreme spectral band detection, low noise active reset CMOS architecture, and high-resolution X-ray imagery using these sensors.

These linear image sensors are ideal for visible, ultra violet to visible, and visible to near infrared spectrometers, and their enhancement makes them suitable for spectroscopy applications. The design of their pixels being tall and narrow helps light distribution from a spectrometer’s grating. If provided with UV sensitivity, these sensors do not need extra UV coating.

CMOS 1421 displays superior linearity, which is of extreme benefit to spectroscopy measurements. The device also includes an electronic shutter along with a built-in timing generator, which are useful in spectroscopy. The device is suitable for several applications involving scientific, industrial, and commercial activities.

New sensors based on CMOS match features with those of CCDs. Featuring simpler external circuit design, and simpler operation, CMOS 1421 linear image sensors are suitable for spectroscopy, displacement measurement, barcode scanning, and imaging.

What are 3-D Image Sensors?

3-D image sensors from Infineon are perfect for use in mobile consumer devices. These new REAL3 image sensors measure the time-of-flight of infrared signals, enabling sensing gestures the user makes in front of the screen. Infineon has designed the sensors with a perfect combination of power consumption, performance, functionality, cost, and size. The IRS238xC 3-D image sensors work in any kind of ambient light conditions and this makes them indispensable for reliable use in mobile applications.

The IRS238xC has high-performance pixel arrays that are highly sensitive to infrared light of 850 and 940 nm wavelength. This allows the device to perform unparalleled in any outdoor environment. Combined with this, Infineon has provided its patented SBI or suppression of background illumination circuitry in every pixel. The combination extends the nominal dynamic range of each pixel by nearly 20 times.

As the single-chip design has a high integration level, it allows the user to optimize the bill of material. Apart from this, it also reduces the design complexity and offers a small form factor. There are other advanced features as well, such as integrated high-performance ADCs, illumination control logic, a modulation unit with high flexibility, and circuitry for eye-safety that enables it to work as a laser-class-1 device. Interfacing is through a high-speed CSI-2 data interface.

The IRS238xC operates from an optimized in-built voltage supply unit, and it can self-boot as it has a full SPI master memory interface. Among the new features available on the sensor are, coded modulation and enhanced configuration flexibility. This allows the device to perform flexibly and robustly in multi-camera scenarios and similar use-cases.

The time of flight technology from Infineon works with stability, as high assembly yields prove, and this is a great boon for camera module manufacturers, as the IRS238xC not only simplifies calibration efforts, it also simplifies the camera module design. In short, IRS238xC combines the benefits of reliability, cost, size, functionality, and power consumption, making it indispensable for mobile 3-D sensing applications in all kinds of ambient light conditions.

For instance, the IRS238xC has the smallest module size giving 224 x 172 pixels, each of size 14 µm and with their own individual micro-lens. The suppression of background illumination or SBI provides each pixel with a 20-time gain in dynamic expansion against strong sunlight, but at minimum power consumption. The robust high-volume assembly of the device and its low calibration efforts offer an easy design and low system bill of materials for the designer.

IRS238xC offers time-of-flight technology for directly measuring the amplitude and depth of information in every pixel. It does this using a single modulated infrared light source that the chip emits to the whole scenery. The TOF imager captures the reflected light. The unit measures the phase difference between the emitted and the reflected light along with their amplitude values, thereby calculating the distance information and producing a grayscale picture of the entire scene all in one sweep.

Infineon provides algorithms that feature unique multiple benefits compared to other depth sensing technologies such as stereovision or structured light.

Raspberry Pi and Traffic Lights

Although we come across traffic lights almost every time we step out of our homes, we rarely stop to think about how they work. However, Gunnar Pelpman has done just that, and he has put the hugely popular single board computer, Raspberry Pi to good use. While most of the tutorials introduce turning on and off LEDs, he has prepared a somewhat more complex tutorial, one that teaches how to program traffic lights. Moreover, he has done this with the Raspberry Pi (RBPi) running the Windows 10 IoT Core.

Traffic Lights may look very complicated installations, but they are rather simple in operation. They mostly comprise a controller, the signal head, and the detection mechanism. The controller acts as the brains behind the installation and controls the information required to light up the lights through their various sequences. Depending on location and time of the day, traffic signals run under a variety of modes, of which two are the fixed time mode and the vehicle actuation mode.

Under the fixed time mode, the traffic signal will repeatedly display the three colors in fixed cycles, regardless of the traffic conditions. Although adequate in areas with heavy traffic congestion, this mode is very wasteful for a side road with light traffic—if for some cycles there are no waiting vehicles, the time could be more efficiently allocated to a busier approach.

The second most common mode of operation of the traffic signal is the vehicle actuation. As its name suggests, the traffic signal adjusts the cycle time according to the demands of vehicles on all approaches.

Sensors, installed in the carriageway or above the signal heads, register the demands of the traffic. After processing these demands, the controller allocates the cycle time accordingly. However, the controller has a preset minimum and maximum cycle time, and it cannot violate them.

The hardware for the project could not be simpler. Gunnar has used three LEDs—red, orange, and green—to represent the three in a traffic light. The LEDs have an appropriate resistor in series for current limiting, and three ports of the RBPi drive them on and off. The rest of the project is the software, for which Gunnar uses the UWP application.

According to Gunnar, there are two options for writing UWP applications—the first a blank UWP application and the second a background application for IoT—depending on your requirement. The blank UWP is good for trying things out as a start, as, at a later point of time, you can build a User Interface for your application.

After creating the project with the blank UWP application, Gunnar added a reference to Windows IoT Extensions for the UWP. Next, he opened the file MainPage.xaml and added his own code, which begins with a test for the wiring. He uses the init() function to initialize the GPIO pins and stop() to turn all LEDs off. Then the code turns on all LEDs for 10 seconds to signal everything is working fine.

According to Gunnar, the primitive code mimics the traffic lights. He uses a separate code for the cycling of the traffic lights, and another for blinking them on and off. He uses the play() function for running ten cycles of the traffic light.

Condition Monitoring with MEMS Accelerometers

In the market today, several condition-monitoring products are available as easy to deploy and highly integrated devices. A vast majority of them contain a microelectromechanical system or MEMS accelerometer as their core sensor. Not only are these economical, they also help in reducing the cost of deployment and ownership. In turn, this expands the facilities and the number of equipment benefitting from a condition monitoring program.

Compared to the legacy mechanical sensors, solid state MEMS accelerometers offer several attractive attributes. So far, their low bandwidth had restricted their application for use in condition monitoring. For instance, the noise performance of MEMS accelerometers was found to be not sufficiently low to cater to diagnostic applications requiring low noise levels over bandwidths beyond 10 KHz and over high frequency ranges.

The above situation is changing. Although still restricted of a few KHz of bandwidth, MEMS accelerometers with low noise are now available allowing the designers of condition monitoring products to use them in their new product concepts. This is because the use of MEMS brings several valuable and compelling advantages to the designer.

For instance, the size and weight of the MEMS accelerometers are of the utmost importance to airborne applications in health and usage monitoring systems, especially as they employ multiple sensors on a platform. MEMS devices in surface mount packages in a triaxial formation provide very high performance, while their footprints are only 6 x 6 mm, and weigh less than one gram. This shrinks the final package, while the interface of a typical MEMS device uses a single supply, which makes it easier to use in digital applications by saving on cost and weight of cables.

The triaxial arrangement is simpler with solid-state electronics and the small size of the transducers. They offer a small form factor enabling mounting on a printed circuit board, with the assembly hermetically sealed in housing suitable for fitting on a machine. MEMS devices require very low levels of power from single voltage supply and simple signal conditioning electronics, suitable for battery-powered wireless products.

Designers are able to use MEMS accelerometers in industrial settings for easy transition to digital interfaces now common. This is because the topology of the signal conditioning circuit for MEMS devices is common with both analog and digital output variations, allowing them to adapt the sensors to a wider variety of situations.

For instance, designers can load open protocols such as the Modbus RTU into a micro-controller, while using them with easily available RS-485 transceiver chips. Using surface mount chips, designers can lay out the complete solution for a transmitter with small footprint and fit them within relatively small board areas. They can insert these assemblies into packages, hermetically sealing them for supporting intrinsically safe characteristics or for conforming to environmental robustness certifications.

Although the current generation of MEMS devices can safely withstand 10,000 g of shock according to their specifications, in reality they can tolerate much higher levels without affecting sensitivity specifications. For instance, automatic test equipment can trim the sensitivity of a high-resolution sensor to remain stable over time and temperature to 0.01°C.

What is Raspberry Shake and BOOM?

The Earth below our feet is never still. Although we feel tremors only when they are substantially strong, such as during earthquakes, we can use the highly popular single board computer, the Raspberry Pi or RBPi to monitor what is happening just under us. This tiny seismograph, with an appropriate name of Raspberry Shake, is the smallest one can find.

Although small, Raspberry Shake can record earthquakes of all magnitudes, even those no human senses can detect. It is also capable of recording those huge destructive quakes that occur regularly around the globe. Raspberry Shake has a companion, the Raspberry Boom, and it detects infrasonic sounds given off when the Earth shakes.

During earthquakes, the Earth gives off low frequency sounds that are below the threshold of human hearing, but infrasound travels large distances. Other objects also generate such infrasound, including traffic, trains, airplanes, wind farms, weather systems, meteorites, and many more. The Raspberry Boom is the perfect companion to the Raspberry Shake for detecting and studying infrasound.

You only have to snap the Raspberry Shake and Boom on to an RBPi. The two together form a super capable Earth monitoring network. Plugging their output into a Station View then allows creating a powerful array for monitoring and discovering several fascinating events from around the world in real time.

The Raspberry Shake and Boom combine several technologies. The Raspberry Shake has a powerful processor on its main board, and a digitizer with built-in sensors including a geophone or super-sensitive motion sensor for detecting Earth movements. You can plug this Shake board right into the RBPi board, which will power it. The data from the Shake board uses miniSEED for processing, as this is a standard data format the industry uses. The output is also compatible with jAmaSeis, and that makes it easy to learn, monitor, and analyze.

Other advanced options on the Raspberry Shake allow experienced users to use it by programming their own protocols such as the IFTTT. They can also laser print their own enclosures. Other users, especially novices, can also use the Raspberry Shake easily, as the design of the devices allows them to be plug-n-play. Their design is professional and anyone can use them on home monitors.

Anyone can use the Raspberry Shake range. For instance, Educational facilities, consumer interest groups, professional institutes, makers, RBPi enthusiasts, citizen scientists, hobbyists, and more can simply plug into the network of Raspberry Shakes to start watching the planet vibrate.

It is very easy for any school or university to access data from any Raspberry Shake anywhere in the world, allowing them to monitor seismic activity of any active earthquake area as well as of quiet regions anywhere. They can view any event such as those demonstrated in IRIS Teachable Moments, including micro-tremors or other larger events.

The Raspberry Shakes are compatible with SWARM analytical software and jAmaSeis. This made the Oklahoma Geological Survey acquire 100 units for expanding their network. They rolled these units to schools and educational institutional facilities for raising the awareness and providing valuable educational tools.

What are RTUs – Remote Terminal Units?

Nowadays, small computers make up remote terminal units or RTUs and SCADA units. Users program controller algorithms into these units, allowing them to control sensors and actuators. Likewise, they can program algorithms for logic solvers, power factor calculators, flow totalizers, and many more, according to actual requirements in the field.

Present RTUs are powerful computers able to solve complex algorithms or mathematical formula describing external functions. Sensing devices or sensors gather data from the field, sending the signals back to the RTU. By solving the algorithms in it using the input signals, the RTU then sends out control instructions to valves or other control actuators. As scan periods in RTUs are very small, the entire activity happens very fast, hardly taking a few milliseconds, with the RTU repeating the process.

Regulatory agencies certifying RTUs prefer use of dedicated hardware for solving certain safety related functions such as toxic gas concentration and smoke detection. Therefore, they make sure of the reliability of detection for safety related functions.

The RTU operates in a closed system. Sensors measure the process variables, while actuators adjust the process parameters and controllers solve algorithms for controlling the actuators in response to the measured variables. The entire system works together based on wiring or some form of communication protocol. This way, the RTU enables the field processes near it to operate according to design.

Before the controller in the RTU can solve the algorithm, it has to receive an input from the field sensor. This requires a defined form of communication between the RTU and the various sensors in the field. Likewise, after solving the algorithm, the RTU has to communicate with the different actuators in the field.

In practice, sensors usually feed into a master terminal unit or MTU that conditions their input, changing it to the binary form from the analog form, if necessary. This is because sensors may be analog or digital types. For instance, a switch acting as a sensor can send information about its state using a digital one or +5 V when it is open and a digital zero or 0 V when it is closed. However, a temperature sensor has to send an analog signal or a continuously varying voltage representing the current temperature.

The MTU uses analog to digital converters to convert analog signals from the sensors to a digital form. All communication between the MTU and the RTU is digital in nature, and a clock signal synchronizes the communication.

The industry uses RTUs as multipurpose devices for remote monitoring and control of various devices and systems, mostly for automation. Although industrial RTUs perform similar function as programmable logic circuits or PLCs do, the former operates at a higher level as RTUs are basically self-contained computer units, containing a processor and memory for storage. Therefore, the industry often uses RTUs as intelligent controllers or master controller units for controlling devices that automate a process. This process can be a part of an assembly line.

By monitoring the analog and digital parameters from the field through sensors and connected devices, RTUs can control them and send feedback to the central monitoring station for industries dealing with power, water, oil, and similar distribution.

Do It Yourself Blynk Board

Those who have some experience with Do It Yourself (DIY) electronic projects, and are just starting to test the waters in the Internet of Things (IoT), the Blynk Board from SparkFun is an activity filled challenging exercise. Both experienced users as well as beginners will find this fun to set up and learn—the kit comes with more than ten projects.

Of course, you can make this board work without the IoT Starter Kit from SparkFun, but then you will have to buy the sensors and other components separately to complete the projects. The Blynk Board, based on the ESP8266, runs on a 32-bit L106, a RISC microprocessor core running at a speed of 80 MHz. It has 1 MiB flash built-in, and allows single-chip devices to connect with Wi-Fi, IEEE 802.11 b/g/n. The board has the TR switch integrated, LNA, balun, power amplifier, matching network WPA/WPA2 or WEP authentication, and can connect to open networks. Other features include 16 GPIO pins, I2C, SPI, I2S, UART with dedicated pins, and a UART (transmit-only) capable of being enabled from GPI02. The board also has a 10-bit successive approximation ADC.

Blynk Boards, based on the ESP8266, come preloaded with projects that are ideal for those just beginning on the Internet of Things and concepts of basic electronics. Arduino boards used it originally for implementing Wi-Fi enabled hardware projects; the ESP8266 has built-in Wi-Fi, making it a cheap, Arduino-compatible, and standalone development board. Many other kits use this board in different shapes and sizes, and you will find it in SparkFun ESP8266 Thing, Adafruit HUZZAH, and NodeMcu.

As the ESP8266 is useful as an open source hardware, it is a useful device for starting with the Internet of Things. It makes the Blynk Board an ideal platform for controlling single board computers such as the Raspberry Pi, and Arduino. Basically, the Blynk consists of three components—a Blynk app for smartphones, the Blynk library, and the Blynk server. The library is compatible with a large number of maker hardware.

While the Blynk library and Blynk server are open source, anyone can use the Blynk app on iOS and Android smartphones. With the Blynk app, you can build a graphical interface for any IoT project—simply drag and drop the widgets. Blynk offers several widgets such as LC display, buttons, and joystick, with which you can start hacking and you need only an IoT development board.

After collaborating with SparkFun, Blynk created the ESP8266 based SparkFun Blynk Board. They offer it fully programmed for more than ten Blynk projects. That makes the IoT Starter Kit from SparkFun with the Blynk Board such a fun project, offering a wonderful introduction to the Internet of Things technology and you do not have to learn any difficult programming.

For those who already have other ESP8266 development boards, simply reprogramming them with the firmware will turn them into DIY Blink Boards. With these, you can easily run boot camps or conduct workshops. Just adding the sensors and a few other components will help you complete the built-in projects, and these you can buy from SparkFun.

Low-Side & Hi-Side Current Sensing

Electronic systems tend to manage their power consumption to reduce the production of heat as waste. This calls for optimizing the system efficiency by effectively distributing power. As the voltage applied to the circuit is usually a constant, engineers monitor power consumption by keeping track of the current drawn by the circuit—power being the mathematical product of the current and voltage fed to the circuit. Current sensing has additional advantages, mainly that of maintaining the health of the system, preventing circuit faults from turning disastrous, and preventing batteries from over-discharging.

Engineers use two basic methods to monitor electric current. The first method follows Ampere’s law, and engineers measure the magnetic field surrounding a current-carrying conductor. The second method follows Ohm’s law, and engineers measure the voltage drop across a small resistor inserted in series with the circuit. The first is a non-intrusive method, but useful only for regularly changing currents, such as alternating current. It is also an expensive method, rather prone to temperature coefficient errors and effects of non-linearity. The second method is simpler, but introduces an element of insertion loss.

The semiconductor industry offers resistive-sensing techniques that are cost-effective and accurate, while making measurements suitable for various applications running on direct current. The resistive-sensing technique relies on sensing the current on the low-side or on the high-side of the circuit, the optimal approach depending on the application.

In resistive sensing, engineers insert a low-value resistor in series with the current path. This produces a small voltage drop in proportion to the current the circuit is consuming and which passes through the resistor. An electronic sense amplifies this tiny voltage to make it easier to process further. However, the sense resistor’s placement depends on the environment of the application and this can present some serious challenges for the sense amplifier.

If the position of the sense resistor is between the load and the circuit ground, a single operational amplifier, acting as a sense amplifier, is adequate to amplify the resulting voltage drop. Engineers call this low-side sensing, and is different from high-side sensing, where they place the resistor between the positive lead of the supply and the load.

In both cases, the sense resistor must be of adequately low value to prevent it from dissipating high power, but its value must be high enough for it to generate a detectable voltage for the sense amplifier to multiply it accurately. The sense amplifier multiplies the difference of voltage across the sense resistor, but uses a common-mode voltage for the purpose.

For low-side sensing, the common-mode voltage is close to the ground, and the rest of the circuitry following the sense amplifier may run on low voltage. However, high-side sensing requires the common voltage to be close to the supply voltage, and sometimes this may be high enough to present supply voltage problems for the circuit following the sense amplifier.

Some applications are unable to tolerate the tiny voltage drop introduced by the sense resistor on the low-side. The situation aggravates as the load current increases. For them, engineers have to follow high-side sensing inevitably.

A Smart Development Board for the Raspberry Pi

The Raspberry Pi or RBPi single board computer when fortified with Cloudio makes a personal IoT computer that users can play with or use for prototyping. Cloudio, the add-on board suitable for the RBPi, offers advanced features such as sensor monitoring and displaying on dashboard, providing custom notifications with image and video, unlimited cloud services, one tap upload for multi-boards, voice assistant capabilities, IFTTT integration, drag and drop programming for Android and iOS, and much more.

As a smart development board kit, Cloudio offers drag and drop programming using the included GraspIO Studio app. Users get a block-based approach that is fairly intuitive. For IoT developers, this approach allows them to reach their goals faster, as the simple but powerful mobile IDE simplifies the complexity of software development.

On the hardware side, the Cloudio kit includes an OLED display, a light sensor, temperature sensor, a mini servo port, a tactile switch, three ADC ports to handle external sensors, three ports for digital outputs, an RGB LED, and a buzzer. This provides the user nearly all the tools necessary for an IoT project. On the software side, the kit comes with the GraspIO, which provides unlimited cloud service, allowing the user to program and manage Cloudio from their mobile devices.

GraspIO provides the user with a block-based feature. Users can treat program modules as blocks, dragging and dropping the blocks as necessary to combine them to achieve various functionalities. This feature offers users with an intuitive mobile interface.

Users can monitor the sensors they attach to the RBPi and arrange their response to be studied in a dashboard. They can set up sensor monitoring projects easily and configure the dashboard to exhibit their response in an intelligent and responsive manner. The kit allows plotting the sensor response in real-time graphs on a mobile device, and exporting data for IoT analysis.

Users can manage several Cloudio kits at the same time, as they can connect their mobile devices to the IoT Cloud Service. Therefore, users can connect to, program, control, monitor, and manage several kits with a single smartphone. The IoT Cloud Service comes with a lifetime offering of 100 daily non-cumulative calls, along with a bunch of 50,000 free preloaded calls.

The IoT Cloud Service also helps in voice control and speech recognition. Users can create their own voice assistants, and add custom voice commands including their own wake-word.

For instance, with the Cloudio Smart Development Board hooked up with the RBPi, a user can interface the RBPi and a USB camera, using the in-app camera block to capture images, videos, and even create GIFs or time-lapse videos. The user can add several features to their projects, including custom email, images, and video notifications.

The Cloudio kit enables features such as adding speech outputs to projects. Therefore, users can make their projects respond with voice outputs, using the easy to use in-app speak block that comes along with the kit. Other features the kit offers are creating real-time speech notifications, custom messaging, or playing recorded audio from the board.

Measuring Very High Currents

High currents, such as 500 Amps and above, are common nowadays. Industries regularly use equipment consuming high currents, and vehicle batteries experience very high currents for a short time during starting. With vehicles increasingly trending towards their electric versions, it is becoming necessary to be able to measure high currents with precision. Increasingly, it is increasingly becoming critical to monitor current consumed accurately for ensuring performance and long-term reliability.

Current sensing is necessary for essential operations such as battery monitoring, DC to DC converters, motor control, and so on. Device specification mainly defines the performance of any current sensor solution. This includes the efficiency, precision, linearity, bandwidth, or accuracy. However, for designers designing a system to satisfy all the requirements of the specifications can be a challenging task. One way to do this is to use a precision shunt, a shunt monitor, and a signal conditioner.

The ±500 A precision shunt-based current sensor design from Texas Instruments (TI) has an accuracy of 0.2% of full scale reading (FSR) over a huge temperature range of -40 to +125°C. Several applications such as motors and battery management systems require such precision current sensing. In general, these applications suffer from poor accuracy caused by shunt tolerances, temperature drift, and non-linearity. Shunt monitors such as INA240, and signal conditioners such as PGA400-Q1 from TI help to solve these problems.

The design from TI works on 48 V or 12 V battery management systems and is suitable for measuring ±500 A, with both high- and low-side current sensing. It accurately compensates for temperature and non-linearity to the second order with an algorithm. Furthermore, it offers protection against harness faults such as input/out signal protection, reverse polarity, and overvoltage. TI has protected its design from electromagnetic interference.

Several ways of measuring currents are available, and these include using magnetic saturation, magneto-resistance methods, Lorentz force law, Ohm’s law, Faraday’s induction law, and more. While each technology presents its own advantages and disadvantages, every customer has his or her own preference and place of use for the specific topology they prefer to choose.

The simplest and most common technology makes use of Ohm’s law, which this TI design also uses. When designing the system for measuring currents, essentially the designer must choose where the current is to be measured—high side or low side, the range of measurement, and whether the current is uni-polar or bi-directional. These parameters define the suitable topology and the design the designer must use. Most vehicle systems now prefer to use 48 V and this new trend implies the current sensor will have to measure a large span of range.

The method of measurement follows a simple process. The ±500 A current passes through the shunt whose resistance measure 100 µΩ. This causes a noticeable amount of voltage drop across the shunt. The current sense monitor INA240 measures this small amount of voltage and passes it on to the signal conditioner, PGA400-Q1. The delta-sigma ADC micro-controller inside PGA400-Q1 creates a ratio-metric voltage between 0.5 and 4.5 V using its linearity and compensation algorithms.