Tag Archives: sensors

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.

Sensor Nodes Based on the Raspberry Pi

Building sensor networks is economical if a microcontroller hosts the sensors. However, sometimes the computational power a microcontroller offers is not adequate. For instance, it may be necessary to convert the data to a different format, print a hard copy of the sensor data, or incorporate the data within an application. What you need is a computer that not only has more processing power, but also allows the use of common applications, affords access to peripherals, and permits the use of scripting languages.

Although the use of an inexpensive personal computer would be of great advantage here, using them as sensor nodes in the networks has its own disadvantages. The primary hurdle is most personal computers are built for use as servers or desktop computers, and almost no general-purpose input/output ports are available. Of course, a data collection card added to the personal computer will serve the purpose, but the cost of the computer added to that of the data-collection card makes the cost of the sensor node uneconomical.

Fortunately, single board computers such as the Raspberry Pi (RBPi) provide an easy solution to the above problem. With sufficient processing power and memory, use of standard peripherals, supported programmable I/O ports, and a small form factor, the RBPi is the most suited for building sensor networks economically.

Essentially, the RBPi is a single board computer that runs Linux as its operating system. To get started with the RBPi, you need a few additional things, such as a USB power supply rated at 2 A with a male micro-USB connector, an HDMI monitor, a keyboard, an optional mouse, and most importantly, an SD card to hold the OS.

The most commonly used operating system for the RBPi is the Raspbian image provided by the Raspberry Pi Foundation on their download page. Once you have downloaded the image, you will have to unzip it and write it into an SD card. The easiest way to do this with a Windows PC is to use the Win32 Disk Imager software. Those on the Mac OS X or the Linux PC may use the dd command.

Now it is time to boot up your RBPi board. Plug in the SD card holding the new image, plug in the keyboard, mouse, and the monitor. Once all the peripherals are in place, plug in the USB power and turn on the power. When prompted to enter a username and password, use Pi and raspberry respectively, and configure the system to your requirement.

For connecting and experimenting with sensors, you may use expansion boards, but using a simple prototyping board instead is more flexible. Using a Pi Cobble Breakout board or similar allows a simple ribbon cable from the GPIO connector on the RBPi to the prototyping board, with the pins arranged in the same order as those on the RBPi are.

Be careful to make or change connections with the RBPi powered off. Also double-check all connections are rightly connected. The GPIO on the RBPi is not protected against short circuits and high voltages, and is easily damaged.

Measuring Air Quality with IoT Sensor

Bosch Sensortec is making an IoT environmental sensor for measuring air quality. The BME680 can measure the indoor air quality, relative humidity, barometric pressure, and ambient air temperature. It has four sensors housed within a single LGA package measuring 3x3x0.95 mm, and both mobile and stationary IoT applications can use the package for use in smart homes, offices, buildings, elder care, sports, and fitness wearables.

The BME680 measures the indoor air quality through its internal gas sensor by detecting a wide variety of gases in the range of parts per billion. The gases it can detect include hydrogen, carbon monoxide, and volatile organic compounds. While measuring altitude and pressure, the BME680 is accurate to within ±1 m and ±12 Pa respectively. Its temperature measurement capability extends from −40°C to +85°C, and it can measure relative humidity from 0% to 100%. In addition, the BME680 can measure an offset temperature coefficient of 1.5 Pa/K.

The BME680 consumes current according to its measuring parameter. While capable of operating from a supply voltage of 1.71 V to 3.6 V, it has a data refresh rate of 1 Hz. When measuring temperature and humidity, the BME680 consumes 2.1 µA, and 3.1 µA when measuring temperature and pressure. The current consumption goes up to 3.7 µA when measuring pressure, temperature, and humidity, while the maximum consumption is between 0.09 and 12 mA when the device is measuring gas, temperature, humidity, and pressure. Therefore, although the current consumption depends on its operating mode, its average current consumption in sleep mode goes down to 0.15 µA.

As an integrated environmental sensor, Bosch Sensortec has developed the BME680 specifically suited for mobile applications and wearables. As for both applications the size and low power consumption are key requirements, Bosch Sensortec has expanded its existing family of environmental sensors by adding the BME680 to its repertoire, while integrating the temperature, humidity, pressure and gas sensors, all of which are highly linear and highly accurate.

The BME680 comes in an 8-pin metal lid LGA package measuring only 3x3x0.95 mm. Bosch Sensortec has designed the sensor for optimized consumption that depends on its specific operating mode, high EMC robustness, and long-term stability. The specialty of the gas sensor within the BME680 is it can detect a wide spectrum of gases for assessing the indoor air quality for individual well-being. For instance, the BME680 can detect VOC or volatile organic compounds from alcohol, adhesives, glues, office equipment, furnishings, cleaning supplies, paint strippers, lacquers, and paints based on formaldehyde.

Applications for the BME680 are numerous. It can be used for altitude tracking as well as calorie expenditure for sports activities. It is sensitive enough for indoor navigation as it can detect change of floors and elevation. As GPS enhancement, it can improve time-to-first-fix, slope detection, and dead reckoning. As home automation control, the user can use the BME680 as an advanced HVAC control. Scientific experiments can use it for measuring volume and airflow, while agriculturists can use it as warning against dryness or high temperature. Sports enthusiasts can use it for monitoring fitness, well-being, detecting skin moisture, change in room, and for context awareness. BME680 is suitable for use as a personalized weather station and for indoor air quality measurement.

Sensing Temperature with NTC Thermistors

Temperature sensors using NTC thermistors are built from sintered semiconducting ceramic material. Such materials contain a mixture comprising several metal oxides. The specialty of these materials is they possess charge particles, which allow current to flow through the thermistor, and display large changes in its resistance value even when the change in temperature is rather small. The manufacturing process allows standard NTC thermistors to operate effectively in the temperature range between 50 and 150°C, with glass-encapsulation type of thermistors going up to 250°C.

Thermistors come in a large variety of sizes and styles. These include glass encapsulated, customizable probe assemblies, surface mount types,, disc types, and chip styles. The large variety is necessary as individual attributes of each style gives them the ability to perform effectively in several different industries, while adapting to various and different application requirements.

For instance, industries using NTC thermistors for measuring temperature include telecommunications, medical, healthcare, military, aerospace, automotive, industrial, HVAC, among many others. On the other hand, applications for NTC thermistors cover time delay, volume control, circuit protection, voltage regulation, temperature control, temperature measurement, temperature compensation, and more.

Now, the availability of precision interchangeable NTC thermistors eliminates the necessity of individual calibration for each thermistor. Capable of accuracies of ±0.05°C, the interchangeable thermistors are now gaining popularity as industry standard. Their standard resistance values usually range from 2.25 kilo-ohm to 100 kilo ohm, with temperature coefficients of -4.4% per °C or -4.7% per °C.

Interchangeable NTC thermistors offer extreme accuracy when sensing temperature. This makes these versatile sensors an excellent choice for use in industries focussing on temperature measurement and control. These industries include, among others, aerospace, HVAC, automotive, industrial, and medical. Applications for interchangeable NTC thermistors include temperature sensing, temperature measurement and control, temperature measurement, and control.

Using interchangeable NTC thermistors in the industry offers several benefits and features. These include beta of 3435 K to 4143 K, RoHS compliance, dissipation constant of 1 mW/°C, fast thermal response times, wide range of ohmic values, a thermal time constant of 7 secs, and fast measurement times. Aging is slow as these NTC thermistors show less than 1% change in resistance even after a span of 10 years. That means, there is no need to recalibrate the system when replacing the thermistor. This certainly reduces operating costs and system downtimes.

Glass encapsulated NTC thermistors are a special breed that are hermetically sealed. This allows the micro-sized sensors to eliminate reading errors from moisture penetration. As they are hermetically sealed, they function effectively in extreme conditions of temperature, pressure, and other severe environmental conditions. The extreme operating conditions allow glass encapsulated NTC thermistors to target markets such as industrial, automotive, medical, and HVAC.

Glass encapsulated NTC thermistors are good for applications involving outdoors such as infrared lighting systems, medical such as those relying on airflow/respirators, industrial such as those including monitoring of terminal temperatures of battery packs while charging, common household appliances such as in coffee makers, ovens, and refrigerators, HVAC such as for temperature measurement and control.

Apart from greater accuracy and faster response times, Glass encapsulated NTC thermistors offer high precision resistance and beta value with a huge operating temperature range.

How to Select Current Sensors?

To select an appropriate AC current sensor for an application, you must know the operational frequency range and the current rating the sensor will encounter. Additional considerations that you will need to decide are the type of the sensor, its mounting (through-hole or surface mount), turns ratio, and the overall dimensions.

Sensor type refers to a sensor only configuration, where a conductor integral to the application forms the primary. Another type could be a complete current transformer where the primary is included as a winding. Engineers typically use current sensors to measure and control the load current in control circuits, safety circuits, and power supplies. Power supplies usually require accurate control of current, and this requires sensing the magnitude of the current accurately.

Irrespective of whether you are using the sensor or transformer, the highest flux density handled is dependent on the worst-case current and frequency faced by the device. However, note that exceeding 2000 Gauss will mean most AC current sensors output will be non-linear. Therefore, the current through the sensor and its output voltage will no longer remain proportional, as the magnetic core of the sensor saturates at very high flux densities. To keep the flux density below the saturation limit, it is necessary to use higher secondary turns.

For instance, in wire-through-the-hole style of current transformers, looping additional primary turns through the hole can dramatically reduce the turns ratio, provided the wire diameter and the hole size permit. Increasing the primary turns allows the use of a higher input current transformer to provide higher output voltage across the terminating resistor on the secondary.

Manufacturers of current transformers offer online tools to help designers select the right current sensor or current transformer for specific application conditions. Initially, the user has to select the type of sensor—a transformer or a sensor only. The next selection is the preferred mounting style—SMT or Through-hole. The online tool also requires other parameters such as the maximum sensed current expected in amperes, the input frequency in kHz, the duty cycle of the primary current waveform as a percentage, and the desired output voltage corresponding to the expected maximum input current.

The tool then calculates the required terminating resistance based on the maximum input current, the number of secondary turns and the output voltage—basing the calculations on a single-turn primary. Next, the tool calculates the maximum flux density of the secondary, making sure it does not exceed 2000 Gauss. It does this by taking into account the output voltage, the duty cycle, secondary turns, and the frequency of operation.

The result lists all part numbers of the manufacturer that meet these input conditions, typically including a graph of the output voltage versus the sensed current for the calculated terminating resistance.

To select an appropriate current sense transformer for your application, you require knowledge of the maximum current, frequency, and duty cycle of the sensed current, including the output voltage you require. Using this information, the online selector tools will provide you with the appropriate terminating resistor value and a list of current sensors that meet the conditions of the application.

Inertial Sensing for Automation

In any type of industry, whether it is automotive, unmanned aerial vehicles, energy, logistics, agriculture, or manufacturing, automation brings increasing promises of great gains in terms of efficient utilization of resources, achieving accuracy, and safety. To achieve these gains it is necessary to identify the appropriate sensing technologies that will enhance the contextual knowledge of the equipment’s condition.

As the location or position of an equipment is a valuable input, precision inertial sensors provide accurate location information and help in maintaining accurate positioning. Where mobility is a factor, it is necessary to couple both the location and the contextual sensor information with the application. Operating in a harsh or complex environment often requires determination of position as a critical value. This is where inertial sensors help to make a difference.

Over the years, machinery has evolved from making simple passive movements, to functioning with embedded controls, and now it is moving towards fully autonomous operations, with sensors playing the enabling role. Earlier, for supporting offline analysis or process control, sensors working in isolation were adequate. However, obtaining real-time benefits requires increasingly sophisticated sensor types, while efficient processing requires important advances in sensor fusion. Therefore, increasingly intelligent sensor systems are coming up catering to complex systems on multiple platforms that require the knowledge of states the system has held in the past.

Inertial sensors used with smart machines serve two special functions, one for equipment stabilization or pointing, and other for equipment navigation or guidance. Most systems consider GPS as the most suitable for navigation. However, potential blockages cause significant concerns for many industrial systems. Some systems transition to inertial sensing when GPS is blocked, but this requires the inertial systems to be of sufficient quality to provide the same precision, as did the GPS.

Inertial sensors provide the feedback mechanism in case of servo loop or stabilization for maintaining a reliable positioning such as the antenna pointing angle, construction blade, crane platform, camera, UAV, or farming implement. For all these, the purpose is not only to provide a useful function, but also to deliver a safety mechanism or critical accuracy, even when the environment is incredibly difficult.

In reality, sensor quality matters when good performance is desired. Engineers use sensor fusion for making some correction, for instance, when correcting the temperature drift of sensors, or compensating an accelerometer when correcting for gravitational effects on a gyroscope. In such cases, this helps only in the calibration of the sensor to the environment, but does not improve the ability of the sensor to maintain performance between the calibration points. With a poor quality sensor, the accuracy falls off quickly, as the performance of the sensor rapidly drifts without expensive or extensive calibration points.

Even when using high quality sensors, some amount of calibration is desirable, especially when the aim is to extract the highest possible performance from the device. However, the most cost-effective method of calibration depends on the intricate details of the sensor, along with a deep knowledge of motion dynamics. This makes the compensation or calibration step an embedded necessity for the manufacturer of the sensor.

Specifying Fiber Optic Sensors

The industry prefers fiber optic sensors as they work well in tight spots and in applications that have a high degree of electrical noise. Fiber optic sensors are useful in machines, fixtures, and conveyors for sensing part presence as an important component of industrial automation. The industry often requires controlling sequence and error-proofing assembly based on the presence or absence of a part. In many cases, it is simply impossible to know whether a part is where it should be or the holder is empty as expected. Therefore, verification is only possible by using a presence sensor.

Sensors come in many varieties, including magnetic, capacitive, inductive, and photoelectric. Depending on the application, each type of sensor has its own merits and demerits. Among all the sensors available in the market, photoelectric sensors offer the broadest types and technologies, and suitable for the widest range of applications.

The family of photoelectric sensors includes a large variety of light-emission types that includes lasers of class 1 and 2, visible, and infrared. They also include different sensing technologies such as through-beam, reflective, suppression, background, and diffuse. Different housing configurations are also available such as fiber optics and photo eye. We will focus on specifying and applying fiber-optic sensors, as these offer the most advanced capabilities with options for configuration, and are most suitable for use in tight spots that the photo-eye sensor finds too small.

Fiber-optic sensors are also known as fiber photoelectric sensors, and comprise of two parts—the amplifier and the fiber cable. The amplifier is the electronic part and is actually a fiber photoelectric amplifier. The fiber-optic cable includes the optic sensor head and the fiber cable to transmit light to and from the amplifier.

All photoelectric sensors work with a simple technique. A light emitter produces the source signal and a receiver detects the signal. A large variety of technologies is available for sensing and measuring the light transmitted to the receiver. For instance, standard photo-eyes look for the presence or absence of light, whereas background suppression sensors sense the angle of the returning beam. Other type of sensors measure the time taken by the light to return, thereby providing a measure of distance it traveled.

Simple photo-eyes such as those used in reflective and diffuse units house the emitter and receiver in the same optical sensor head, while through-beam units house them in two optical sensor heads. On the other hand, fiber-optic sensors have all the electronics in a single housing, with a fiber cable connecting the separate emitter and receiver to the electronic housing. Light from the emitters and that coming to the receivers travels through the fiber cables, similar to high-speed data traveling through fiber-optic networks.

The above segregation means the technician has to mount only the sensor head on the machine, while routing the integrated fiber-optic cable and plugging it into the amplifier placed in a safe place such as a control enclosure to protect it from the harsh manufacturing environment.

A large variety of options is available for both fiber-optic cables and amplifiers. These range from basic to advanced, suitable for meeting the demands of increasing functionality, including advanced logic and communication capabilities.