What Is A Sensor and What Does it Do? (2024)

Sensors, also known as transducers, are one of the fundamental building blocks of moderndata acquisition systems(aka DAQ or DAS systems). These systems are comprised of the following basic components:

• Sensors

• Signal Conditioning

• Analog-to-Digital Converter (ADC)

• And some sort of computer with DAQ software for signal logging and analysis.

What do the sensors do?

A sensor is a device that detects the change in the environment and responds to some output on the other system. A sensorconverts a physical phenomenon into a measurable analog voltage (or sometimes a digital signal) converted into a human-readable displayor transmittedfor reading or further processing.

One of the best-known sensors is the microphone, which converts sound energy to an electrical signal that can be amplified, transmitted, recorded, and reproduced.

Sensors are used in our everyday lives. For example, the common mercury thermometer is a very old type of sensor used for measuring temperature. Using coloured mercury in a closed tube, it relies on the fact that this chemical has a consistent and linear reaction to changes in temperature.

By marking the tube with temperature values, we can look at the thermometer and see what the temperature is. The precision is somewhat limited due to the visual size of the scale markings, but it is sufficient for its intended purpose.

Of course, there is no output (other than the visual one). This kind of thermometer, while useful in the oven, or outside the kitchen window, is not particularly useful for data acquisition applications because, in order to record the values from it, we must have an output that can be digitized. So, temperature sensors have been invented to measure temperature and other physical phenomena and to provide an output that we can display, store, and analyze.

Let’s learn more about the most common and popular sensors in use today.

Types of sensors

There are many types of sensors that have been invented to measure physical phenomenon:

• Thermocouples, RTDs and Thermistors: for measuring temperature

• Strain gages: to measure strain on an object, e.g. pressure, tension, weight, etc.,

• Load cells: for measuring weight and load

• LVDT sensors: LVDTs are used to measure displacement in distance

• Accelerometers: measuring vibration and shock

• Microphones: for capturing sound waves

• Current transducers: for measuring AC or DC current

• Voltage transformers: for measuring high voltage potentials

• Optical sensors: used to detect light, transmit data, and replace conventional sensors

• Camera sensors: used to capture single and continuous 2D images

• Digital sensors: used for discrete on/off counting, linear and rotary encoding, position measurements, etc.

• Positioning sensors (GPS): used to capture the longitudinal, latitudinal position based on GPS, GLONASS, and other satellite positioning systems. Different GPS sensors with different accuracy are available.

• and countless more.

Depending on the type of sensor, its electrical output can be a voltage, current, resistance, or another electrical attribute that varies over time. Some sensors are available with digital outputs, whereby they output a series of bytes of scaled or unscaled data. The output of these analog sensors is typically connected to the input of a signal conditioner, which we will discuss in the next section.

Next, we will take a brief look at each of the major sensor types in use today.

Temperature sensors

The most common and popular sensors for temperature measurement include:

• Thermocouples

• Thermistors

• RTDs (PTx)

• Infra-red temperature detectors

Millions of these sensors are at work every day in all manner of applications, from the engine temperature shown on our automobile dashboard, to the temperatures measured in pharmaceutical manufacturing. Virtually every industry utilizes temperature measurement in some way.

Main characteristics of different temperature sensors

Thermocouples

Thethermocoupleis the most popular temperature sensor overall due to its relatively low cost and reliability. Thermocouples are based on the Seebeck effect, which demonstrates that when a pair of dissimilar metals in contact with each other at each end are subjected to changes in temperature, they create a small voltage potential.

Pairing different kinds of metals giveus a variety of measuring ranges. These are called “types.” A very popular one is Type K, which pairs chromel and alumel, resulting in a wide measuring range of −200 °C to +1350 °C (−330 °F to +2460 °F). Other popular types are J, T, E, R, S, B, N, and C.

Thermocouple types J, K, T, and E are also known asBase Metal Thermocouples. Types R, S, and B thermocouples are known asNoble Metal Thermocouples, which are used in high-temperature applications

The output from a thermocouple must be linearized by the measuring system.

It must also be referenced using theCold Junction Compensation (CJC). The “hot junction” is the measuring end of the thermocouple assembly, and the other end is the cold junction, where the reference is typically located.Cold Junction Compensationremoves the effect of the voltages generated by these cold junctions for more accurate temperature measurement.

Thermocouple challenges

Due to the very small microvolt and millivolt output of these sensors, electrical noise and interference can occur when the measuring system is not isolated. Dewesoft modules tackle this head-on with powerful isolation. There is no better way to reject common-mode voltages that get into the signal chain.

Another way to reduce noise is to place the measuring system as close to the sensor as possible. Avoiding long signal lines is a proven strategy for maximizing signal fidelity and reducing costs. Look at ourKRYPTONand IOLITE instruments for best-in-breed solutions here.

An inadequate CJC results in wrong readings. This assembly needs to be protected from ambient temperature changes to provide a solid reference. We use a separate CJC chip for each channel in our CJCs, which are milled from a solid block of aluminum, and precisely assembled to achieve the best possible reference.

Learn more about Dewesoft and thermocouple temperature measurement:

What Is a Thermocouple Sensor and How Does It Work?In this article, you will learn what is a thermocouple, which are the basic types available, and how the temperature is measured with these sensors today.

RTD sensors

Compared to the thermocouple,the RTD (Resistance Temperature Detector)is generally more linear and drift-free within its measuring range. However, due to their platinum content and more complex construction, they are more expensive than thermocouples.

You will typically find RTDs used in applications such as pharmaceuticals, where precise temperature measurements must be made over a long time. They don’t range much above 600° C, however, so thermocouples are a better choice for high-temperature “contact” applications.

Unlike the thermocouple which is self-powered, the RTD must be powered by the measuring system.

The RTD measures temperature via electrical resistance which changes in a highly linear fashion with respect to temperature. Although at its core an RTD is a 2-wire sensor, the addition of one or even two more wires (3 and 4-wire hookup) provides better compensation against self-heating and lead wire resistance and is recommended. Dewesoft signal conditioners provide 2, 3, and 4 wire hook-up possibilities.

Types of RTD sensors

Pt100(“PT” = platinum and “100” = 100Ω at 0°C) andPt1000are the most popular variants of the RTD sensors. There are, however, also other types such asPt200, Pt500,and Pt2000sensors. Dewesoft data acquisition systemssupport the connection and measurement of all types of RTD sensors.

As mentioned, RTD hook-up is more complex than a thermocouple, however, DewesoftDSI-RTD adaptersmake it easy and convenient to connect your sensors to our measuring systems. Noise is always a consideration for any sensor with small output, but our high isolation inputs are the best prevention imaginable.

Another way to reduce noise is to place the measuring system as close to the sensor as possible. Avoiding long signal lines is a proven strategy for maximizing signal fidelity and reducing costs. Look at ourSIRIUSandKRYPTONmodular DAQ systems for best-in-breed solutions here.

Thermistors

Athermistoris a piece of semiconductor made of metal oxides that are pressed into a small bead, disk, wafer, or other shape and sintered at high temperatures. Lastly, they are coated with epoxy or glass.

When a current is passed through a thermistor, you can then read the voltage across the thermistor and determine its temperature. A typical thermistor has a resistance of 2000 Ω at 25ºC. 3.9 percent temperature coefficient.

Thermistors are inexpensive and have a fast response, but they are not linear, have a limited range, are relatively fragile unless mounted inside a probe for protection.

Pros and cons of different temperature sensors

Strain gage sensors

When astrain gage(aka “strain gauge”) sensor is properly aligned and glued onto an object under test, and we apply stress to the object by bending or twisting it, the resistance of the strain gauge will change linearly, and we can then measure it. We can also apply mathematics to calculate strain and other forces.

Strain gage applications

• Strain and stress measurements

• Weight and load measurements

• Force measurement

• Shock and vibration measurements

• Road load data acquisition

Strain gauge sensors pros and cons

Learn more about the strain gages and strain measurement:

What Is a Strain Gauge Sensor and How Does It Work?Strain and pressure sensors are widely used in many static and dynamic measurements. Learn the best practices and theory behind strain gauge measurement.How to Measure Weight With Load Cell SensorsSee how load cell sensors work. Learn how weight measurements are made in science and industry. Understand how you can incorporate them into your testing.

Load cell sensors

If we take another step and permanently affix four strain gauge sensors to a body of a given shape, we create a different sensor called a Load Cell. This is essentially a force or pressure sensor.

The most well-known load cells are the ones installed at the bottom of your digital bathroom scale. When you step onto the scale and compress the load cells, they output a change in resistance, which a microcontroller measures and converts into a value in kg (lbs).

A “bar” or “bending beam” (aka “binocular beam”) load cell is commonly used for industrial weighing applications. One end of the bar is fixed to a structure, while a force is applied to the free end of the sensor (see F in the graphic below).

This force causes the four strain gauges that are built into the top and bottom and each end of the load cell to elongate or compress depending on how much application or removal of the force stresses the load cell structure. These tiny changes in potential from the strain gages are easily converted to weight within ourDAQ system.

Load cells are available in many shapes and sizes: some for very tiny spaces and small loads, and others for huge loads of hundreds of thousands of tons, etc.

Load cell applications

• Materials testing- weighing parts as they are manufactured for consistency

• Aerospace- jet engine thrust, load on wheels and undercarriages

• Marine- mooring line tensions

• Transportation- torque measurements on engines, highway truck weigh stations

• Industrial- tension and force measurements in paper and metals mills

• Medical / Healthcare- Infant incubator scales, physical therapy equipment.

• Construction- Cable forces in elevators, forces on scaffolding

• Entertainment- cable tension tests on cables used to hoist acrobats

• Petrochemical- measuring the forces on oil and gas drilling tools

• Farming and Ranching- weighing livestock, hopper, tankard and silo weighing

• Household / Consumer- digital bathroom scales, kitchen food scales

Load cell sensors pros and cons

Learn more about load cellsand weight measurement:

How to Measure Weight With Load Cell SensorsSee how load cell sensors work. Learn how weight measurements are made in science and industry. Understand how you can incorporate them into your testing.

LVDT sensors

LVDT (linear variable differential transformer)transducers are used to measure linear displacement/position over relatively short distances. They consist of a tube that contains a rod. The base of the tube is mounted to a fixed position, and the end of the rod is affixed to something that moves.

As the rod is pulled out from the tube or slides back in, the sensor outputs a signal that represents the position of the rod from its starting point to its maximum deflection. The rod does not touch the inside of the tube, making it virtually frictionless, and the LVDT itself contains no electronics, making it popular in harsh environments.

LVDT applications

• Thousands of Industrial, factory, and process measurement applications

• Aerospace- actuator and control surface test

• Transportation- monitoring ride height between truck and train body

• Petrochemical- positioning of drilling tools

LVDT sensors pros and cons

Vibration sensors - accelerometers

Accelerometers are used for measuring vibration and shock on machines and basically anything that moves. Their outputs can also be integrated and double-integrated to calculate displacement and velocity.

Accelerometers for making dynamic measurements are normally based on the piezoelectric principle: when a quartz crystal is put under stress it releases a stream of charged ions proportional to the stress. These charge sensors are connected to a charge-type signal conditioner. An even more popular type is IEPE (aka ICP®) sensors, which have an integrated preamplifier, and which require a less expensive signal conditioner.

There are also capacitive-type accelerometers that are based on a different principle and are popular in less demanding industrial applications.

Additionally, there are MEMS-based accelerometers that are heavily used in navigation applications, tablet, and phone orientation, automotive testing, and motion capture.

Accelerometer applications

• Shock and vibrationtests of all kinds, across all industries

• Human body vibrationtests

• Torsional and rotational vibrationtests

• Order tracking analysis

• Preventive maintenance of machinery

• Aerospace- fuselage strain and stress tests, jet and rocket engine vibration test

• Transportation- Recording shock and vibration during transporting fragile items

• Automotive- body panel shock and vibration, passenger comfort tests, engine vibration

• Civil engineering - structural health monitoring

Accelerometer sensors pros and cons

Learn more about the vibration measurement:

Measuring Shock and Vibration with Accelerometer SensorsThe ultimate guide to shock and vibration measurement. Learn what is an accelerometer and what is the difference between various vibration sensors types.

Sound sensors - microphones

In addition to being used in the entertainment industry, microphones are also manufactured to be used in data acquisition applications for analyzing and measuring sound and noise.

Microphones are used in noise and vibration studies, human hearing studies, automotive pass-by noise applications, and thousands more.

Microphone applications

• Noise and vibrationtests of all kinds, across all industries

• Aerospace- Jet engine noise testing

• Transportation- Recording shock and vibration during transporting fragile items

• Automotive- engine noise, pass-by noise test, brake noise tests

• Medical- ambient noise impact studies, hearing testing

Microphone sensors pros and cons

Current transducers

Along with voltage, a current is one of the most fundamental forms of energy that we measure for monitoring and analytical purposes. Whether it’s testing the quality of the energy of the power grid, the energy consumption of a hybrid electric automobile, or a machine, power is critically important.

For small to medium levels of current, we can usecurrent shuntsto convert current to voltage. A shunt is basically a resistor that is installed directly into the circuit where we want to measure the current.

Most of the other kinds of current sensors and transducers on the market operate via induction or a related method whereby they are NOT part of the circuit. This allows much higher currents to be measured. Shown below, is a typical current clamp - a device that detects the electromagnetic field created by a current and measures it. The sensor output is a proportional voltage that ourDAQ systemcan display, store, and later analyze.

There are flexibleRogowsky coilsthat are easy to install even in places where it is difficult to reach, or when disconnecting the circuit is undesirable. There are also zero flux and fluxgate current sensors for high-accuracy applications, especially those in power quality and related fields. There is a broad range of current sensors and transducers, specifically engineered for all kinds of applications.

Current transducer applications

• Energy Production and Distributiontests of all kinds, power quality tests, fossil fuel, and nuclear power plant monitoring

• Aerospace- engine and power system testing

• Automotive- electrical system test, hybrid, and electric motor tests

• Transportation- electric subway cars, third rail and pantograph tests, electrical energy distribution centers

Current transducers pros and cons

Learn more about current measurement and analysis:

How To Measure Current Using Current TransducerWhat is electrical current and how is it measured? Find out in the article and learn the basics of exact current measurements and applications via sensors.

Voltage transformers - potential transformers

Along with current, voltage is one of the most fundamental forms of energy that we measure for monitoring and analytical purposes. Whether it’s testing the quality of the energy of the power grid, or the energy consumption of a hybrid electric automobile, or a machine, power is critically important.

Nearly every DAQ system and data logger in the world can directly accept low and medium voltages in the ranges of 0-10V or 0-50V, so we do not need any transducer to reduce this voltage. From 50V to approximately 1000V there are signal conditioners available for DAQ systems such as theSIRIUS-HVmodule, which can directly and safely accept these voltages and internally step them down so that they can be digitized, displayed and stored.

But at higher voltages, or in any case, when life-threatening currents and voltages are present, it is essential to use a high voltage transformer to step down the high voltage and isolate the human test operator from dangerous voltage and current. Such a device is called either a Voltage Transformer (VT) or a Potential Transformer (PT).

The typical PT uses a transformer to step down a very high potential - even higher than 10kV - down to a safe level. It can be placed in series with or across the circuit being monitored. The transformer’s primary winding has a large number of turns compared to the secondary.

Because the DAQ system connected typically has a very high impedance, very little current will flow, therefore the PT’s secondary winding experiences almost no load at all. Most PTs output between 50 and 200V, which nearly every DAQ system can accept.

PTs are available for outdoor usage and those designed for indoor usage. There are also those designed for electrical metering applications. There is also an alternative to the pure transformer type which uses a bank of capacitors after an intermediate transformer to further step down the voltage. These can be less costly because the relatively low step-down ratio intermediate transformer is less expensive than the conventional wound transformer with a high step-down ratio.

A third variant is the optical VT. Optical VTs are usually found in power substations, and not often in DAQ applications. Since they operate on the principle of the Faraday effect, whereby the polarization of light is affected directly by a magnetic field, they are inherently isolated. They are also extremely accurate.

Voltage transformers applications

• Energy Production and Distributionhigh voltage power line testing, synchronizing generators with the main power grid,

• Aerospace- engine and power system testing

• Automotive- electrical system test, hybrid, and electric motor tests

• Transportation- electric subway cars, third rail and pantograph tests, electrical energy distribution centres

Voltage transformers pros and cons

Learn more about voltage measurement and analysis:

Voltage Measurement in Data Acquisition ApplicationsIn this article, you'll learn what voltage measurement is, which voltage sensors and transducers are available today, and the basics of voltage measurement.

Optical sensors

There are several applications for optics within the sensor market today:

• Sensing light, IR and UV

• Detecting Object Distance, Absence/Presence

• Replacement of Conventional Sensors

Sensing light, IR, and UV

There are countless applications for detecting or measuring how much ambient light is around the sensor. The most obvious examples include automatic switches for turning off or on lights: this requires a photodetector.

Even our mobile phones have a light sensor so that they can automatically adjust screen brightness. Most cars today turn on their headlamps automatically when daylight ends, and even turn on/off high-beams at night when an approaching vehicle is detected. Automatic cameras measure the ambient light in order to set the exposure correctly.

The main technologies used for the applications listed above (and more) include photovoltaics, photocells aka photoresistors. They are designed to detect and measure light.

And although most of these sensors are designed for the human visible spectrum, some are designed to work within the infrared (IR) spectrum and even the ultraviolet (UV) spectrum. The IR spectrum is what many robotic systems use, as well as our television remote controls at home. IR radiation cannot be seen by the human eye, but it can be damaging to our eyes in high doses, so detecting it is important for safety purposes among many other applications.

Aphotocell, also called a photoresistor or LDR (light dependent resistor) can detect the presence and amount of light because of its output changes in proportion with how much light falls on the cell, which has a pattern on it usually made from cadmium sulfide. When no light shines on the cell, its resistance is extremely high. But when light hits the cell its resistance drops in proportion with the amount of light.

Paired with the appropriate signal conditioning, it can be used as an on/off sensor, or to measure the intensity of light. Based on the chemistry of the cell, these small and inexpensive cells can detect all the way into the infrared spectrum.

Detecting object distance, absence/presence

Photodetectorsaka proximity sensors, as well as their semiconductor-based cousin, the photodiode, are used to measure the distance to or between objects, and also to sense either the presence or absence of an object.

These are used in a wide variety of industrial applications, including factory process lines, making sure that objects are spaced properly on a belt, or detecting when a new object is in position on an assembly belt. They are also used in automotive applications, detecting the presence of another car or object, as well as alarm systems, and CD and DVD drives.

Replacement of conventional sensors

The next level is to use optics to do the sensing itself, both augmenting and replacing conventional technology sensors like strain gauges, accelerometers, temperature sensors, and more. More about this new trend will be added to this article in the near future, so please check back.

fiber optic transmission

In addition to sensor performance, another advantage is the fiber optic transmission of the sensor data itself compared to using copper cables.

Today, fiber optics are being used instead of electrical transmission to send signals from one point to another. We see this even in our own homes, where fiber is used to bring television and the internet to our homes at transmission speeds that are higher than conventional cable. Fiber optical transmission also provides several distinct advantages over electrical transmission, including:

• Immune to magnetic interference

• Immune to resistance and heating

• Very long signal transmission path without signal loss

• Multiple signal wires can be reduced to a single thin cable

• Very high bandwidth

Optical sensors applications

• Turning on/off lights automatically, alarm systems

• Factory process applications, assembly lines, conveyor systems

• Robotics, movement direction, and detection

• Smoke detectors

• Medical sample analysis

• Laser range finders, night vision goggles

• Automatic door openers

Optical sensors pros and cons

Camera sensors

We think of cameras as something only used to take pictures or movies, but they are heavily used in all kinds of industrial and scientific applications as well. Factories use single and continuous image sensor cameras (aka video cameras) to monitor and control a wide variety of fabrication and assembly line processes.

Cameras are also an important part of DAQ system measurement applications. In fact, all of theDAQ systemsmade by Dewesoft can utilize one or more video cameras and record video in sync with the analog and digital data that they’re recording.

Professional vs. consumer cameras

On one end of the capabilities spectrum, it is possible to use a very inexpensive web camera to add a video to your recordings in some data acquisition (DAQ) systems. But on the other end are industrial-grade cameras with better lenses and the ability to synchronize the framerate of the camera to the process being recorded and/or with the data acquisition sample rate.

For example, theDS-CAM-600shown here can output up to 336 frames per second at full HD resolution, and up to 600 frames per second if the size of the image is reduced. The camera is also sealed toIP 67so that it can be used in wet, dusty, and harsh environments. Within DewesoftDAQ systems, multiple cameras can be used at the same time, providing different viewing angles of the object(s) under test.

When Dewesoft added the common webcam to its DAQ systems in the early 2000s, it completely revolutionized the DAQ market. The next logical step was using industrial cameras whose frame rates could be precisely controlled, and which offered better resolution and speed.

Mechanical mounting and rugged construction are also critical with any sensor, and this has been designed into today’s best industrial machine vision cameras.

Infrared or thermal cameras

Infrared cameras are also sometimes used in scientific and industrial applications and are another important sensor for DAQ applications. Infrared cameras can “see” the temperatures within its field of view, so it’s the perfect way to measure temperature without making any contact.

Infrared is extremely useful in troubleshooting in power plants because power supplies and generators that are hotter than normal indicate a problem. With one look using an IR camera is it easy to see trouble spots.

The same is true with automotive brake testing, where IR cameras make it possible to measure the precise temperature of the brakes in operation and measure accurately how fast they heat up and cool down under a variety of conditions. They are being used more and more in ADAS (advanced driver assistance systems), as they allow the car to detect people and other sources of thermal energy before they come into view, especially at night.

Being able to “see” in a completely different spectrum opens up many possibilities in virtually every test and measurement application today. The best-known maker of IR cameras isFLIR, and Dewesoft has integrated many of their cameras seamlessly into theirDAQ systemsso that continuous thermographic data can be acquired in sync with the analog and digital sensor data, as shown in the example above.

High-speed cameras

High-speed cameras are useful for capturing extremely fast-changing events. You’ve probably seen slow-motion replays of a balloon popping, or a bullet impacting glass of water - those videos were captured with high-speed video cameras.

High-speed cameras from Photron capture up to 500,000 pictures per second. This data is captured to RAM and then is immediately available for replay. It is possible to synchronize DewesoftDAQ systemswith Photron cameras so that they are both triggered at the same time, and when the test is over, the high-speed video is immediately transferred to the Dewesoft DAQ system and automatically synchronized with the other data. You can replay it in perfect sync with all the data from other sensors.

Summary

Cameras provide a unique context to the data that engineers record, adding a vital layer of information and understanding to countless research and testing applications.

Camera sensor applications

• Industrial cameras: Factory automation and process control;automotivepass-by noise tests, wind tunnel tests, brake tests;aerospacecontrol surface tests, escape slide tests, engine tests

• InfraRed cameras: energy and powertests, automotive ADAS (advanced driver assistance systems)

• High-speed cameras: Ballistics testing; fluid dynamics research; materials testing; automotive crash testing; aerospace wind tunnel testing

Camera sensors pros and cons

Digital sensors

When we talk about digital sensors, we refer to those sensors that output discrete values, usually related to the linear or angular position, as well as those sensors that are used to detect when an object is nearby. Let’s take a look at the most commonly used digital sensors.

Proximity sensors

Aproximity sensoris able to detect a nearby object without making contact with it, and then output a pulse or voltage signal. There are several types of proximity sensors, which are chosen based on the composition of the object(s) that should be detected.

Rotary encoders

Arotary encodertypically provides excellent angle resolution, as they are available with up to thousands of steps per 360° revolution, which allows for steps far smaller than 1°. Many encoders can also detect the direction of rotation, which is essential in some applications.

Incremental encoders

Incremental encoders reportrelative changesin position and direction - they do not track absolute position (angle).

Incremental encoders output A and B signals, which indicate changes in movement and direction. Some of them are capable of being “homed” or referenced to a particular position. When this position is reached an additional Z output signal is generated. Incremental encoders are the most common and popular types of encoders.

Linear encoders

Alinear encodermeasures position along a linear path. Unlike a rotary encoder which has a circular plate inside that allows it to measure shaft position, most linear encoders move along an external scale and determine their position from markings on the scale.

A perfect example is an inkjet printer, which uses a linear encoder to precisely move the printhead back and forth along a scale during printing. High resolution and accuracy are obviously required in this and countless other applications.

The most prevalent sensing technology used with linear encoders is optical, however, there are encoders that also employ magnetic, capacitive and inductive technology. Optical encoders provide the most accuracy and the highest possible resolution, however, care must be taken to prevent contaminants from interfering with their operation.

There are both analog and digital output linear encoders. Dewesoft systems are better suited to digital outputs since they provide A and B outputs very similar to incremental rotary encoders as described in the previous section.

Gear tooth sensors

This angle-based sensor consists of gear with teeth around its circumference plus a proximity sensor of some kind positioned so that when the teeth pass by, they will be detected. This proximity sensor is typically a Hall Effect type, but others are possible. The gear needs to be mounted onto the rotating shaft that we want to monitor.

The Hall effect proximity sensor detects the variation in flux found in the air gap between a magnet and passing ferrous gear teeth. In modern systems, the signal is converted into a binary square wave that is immune to orientation requirements and can follow the gear speed down to a full stop … and detect the first gear tooth that passes immediately upon power on.

Most Hall Effect sensors can detect not only gear teeth passing by, but can also be used to detect holes in disks and plates, ferrous features (e.g., bolts) added to a wide variety of disks and plates, and notches in drive shafts and camshafts.

Digital sensor applications

• Proximity sensors: Counting RPM of rotating shaft (tachometer applications); Counting parts passing through production line; Intersection vehicle detection (buried in the road)

• Rotary encoders: Speed measurement of motors, conveyors, filling systems, pick and place systems; machine speed, position and distance measurements (textiles, pulp & paper, metals manufacturing)

• Linear encoders: CNC machines; Inkjet printers; laser scanners; pick-and-place manufacturing systems; robotics

• Gear Tooth Sensors: Measuring RPM of rotating shafts; engine combustion analysis; torsional and rotational vibration studies

Digital sensor pros and cons

Summary

We hope that you gained a better understanding of what sensors are, how they work, and how they can be applied across a truly mind-boggling range of monitoring and testing applications. Sensor technology is always moving forward, making these sensors better and better, and finding even more efficient ways of making accurate and repeatable measurements. Sensor-based technology itself is constantly evolving.

Admittedly this article has only scratched the surface. There are many more sensors available today, including ultrasonic sensors that use reflected ultrasonic waves to measure distance, chemical sensors for detecting gases and vapors, and so many more.

Detailed information about various sensors

What Is a Strain Gauge Sensor and How Does It Work?Strain and pressure sensors are widely used in many static and dynamic measurements. Learn the best practices and theory behind strain gauge measurement.How to Measure Weight With Load Cell SensorsSee how load cell sensors work. Learn how weight measurements are made in science and industry. Understand how you can incorporate them into your testing.Measuring Shock and Vibration with Accelerometer SensorsThe ultimate guide to shock and vibration measurement. Learn what is an accelerometer and what is the difference between various vibration sensors types.What Is a Thermocouple Sensor and How Does It Work?In this article, you will learn what is a thermocouple, which are the basic types available, and how the temperature is measured with these sensors today.Voltage Measurement in Data Acquisition ApplicationsIn this article, you'll learn what voltage measurement is, which voltage sensors and transducers are available today, and the basics of voltage measurement.How To Measure Current Using Current TransducerWhat is electrical current and how is it measured? Find out in the article and learn the basics of exact current measurements and applications via sensors.Measuring Position and Displacement With LVDT SensorsIn this article, you will learn how to measure position and displacement with LVDT sensors, how they work, and how you can use them in your testing.Measuring RPM, Angle, and Speed Using Digital, Encoder and Counter SensorsIn this article, we will discuss how you can measure digital signals, digital encoders, tachometers and RPM sensors with Data Acquisition (DAQ) systems.