7 hot, new industrial sensors

DN Staff

March 20, 2000

17 Min Read
7 hot, new industrial sensors

Laser gauging sensor and controller in one package

Using laser gauging sensors conjures up images in some minds of bulky equipment and wiring. Banner Engineering Corp. says its new L-Gage(TM) laser gauging sensors change the image by incorporating the laser and the controller into one package. Among the results, says the company: the first less-than-$1,000 sensor in the category. The list price for the L-Gage sensors is $895. With a maximum resolution of 10 microns, applications include calibrating robot arms, wafer profiling, measuring diameter or thickness, and assembly-dimension inspection.

Beyond cutting the cost by packaging the controller with the laser, the company says, it has taken the flexibility in sensing-window sizing associated with its ultrasonic infrared sensors and applied it to laser gauging sensors. TEACH mode programming incorporated with the product enables users to customize their own sensing windows, from 45 to 60 mm or 75 to 125 mm, depending on the specific sensor. Engineers can do the custom window sizing from a remote location. Traditionally, says Banner, sensors come with specific ranges and users have to position them appropriately, without the opportunity to change the position.

The L-Gage sensors are both analog and discrete at the same time. Generally, says Banner, engineers have to choose one or the other. Users can also program the analog signal for three different response speeds: 1, 10, and 100 milliseconds. Discrete speeds are 2, 10, and 100.

The sensors are non-contacting so they can be used with moving processes, including hot and sticky parts. The non-contacting design means they won't wear out, Banner says.

Users can check operating status of the sensors by watching a series of Light-emitting-diode (LED) lights. Green LED indicates power on, output overloaded, and disabled laser. Yellow shows that the discrete load output is conducting. Red means that the target is in the sensing window, and indicates the condition of the received light signal. The tri-color LED shows sensor readiness for programming analog, discrete, or simutaneous analog and discrete. Yellow refers to response time.

The sensors have a die-cast zinc alloy housing, with an aluminum front cover and an acrylic lens cover. Built-in circuits protect the sensors from reverse polarity, over voltage, and transient voltage, Banner says.

The L-Gage sensors have an operating temperature range of -10C to +50C (+14F to +122F), and are available with a 2m (6.5 ft) or 9m (30 ft), seven-conductor shielded, PVC-jacketed attached cable.

Banner Engineering Corp.

Sensor based on CCD laser triangulation

CCDs (charge coupled devices) are the semiconductor photoelectric detectors found in video and digital cameras. They combine high sensitivity and good dynamic response-features that, when combined with an economic price, make them attractive for use in industrial sensors.

One such sensor range, the optoNCDT 1800 from Micro-Epsilon, measures distances and positions based on the principle of optical triangulation. A visible low-energy laser beam using a Class 2 laser with an energy of less than 1 mW is directed onto the surface of the target object. The receiver optical system images the reflected light onto a highly sensitive CCD array which supplies signals proportional to the distance. A high-speed signal processor reads out this information, which is processed in several stages to form an output signal appropriate to the application.

Although conventional triangulation methods produce good accuracy and reliability on target surfaces with diffuse reflection properties, they perform less satisfactorily on surfaces with differing color, roughness, and reflection properties under varying ambient light conditions. The optoNCDT 1800 compensates for these effects with a sophisticated automatic high-speed intensity control of the laser coupled with the high dynamic response of the CCD array.

Johann Salzberger, Micro-Epsilon's marketing manager, says of the new sensor, "The system is very versatile. It easily copes with difficult surfaces ranging from black tire rubber through to freshly machined reflecting metal." For example, says Salzberger, it's no problem measuring highly reflective gear-tooth flanks with this system.

The sensors have a specified measuring rate of 5 kHz, which Micro-Epsilon regards as a high rate for CCD laser triangulation. The system has a range from 2 to 100 mm and can resolve measurement changes down to 0.2 microns. An analog voltage output is provided as standard along with an optional RS232 or RS485 serial digital interface.

Micro-Epsilon Messtechnik

Magnetic induction positioning sensor

Existing position sensor technology is being challenged today by a new engineering approach that is based on the principles of magnetic induction. The detecting element in the new Inductcoder is a combination of magnetic coil and ferromagnetic material. This makes it very resistant to vibration, shock, oil, dust, and extremes of temperature.

To understand this new technology fully, think of the device as having an electrical side (the detector) and an electronic module (the converter).

The detector is very much like a resolver with a ferromagnetic core that is activated by an ac signal. As movement in the equipment shifts the coil through the electrical field of the core, back electromotive force (EMF) is generated in the coil. The electrical signal is changed and this phase difference between the two parts is proportional to the physical displacement between them.

The electronics in the converter generate an internal clock at 10 kHz. It measures the phase-shift deviations from the input and output signals which translate to position.

Users can enhance performance by taking advantage of interpolation software to yield a high-resolution output of 128,000 readings a second-digital output which is effectively analog. Output can be read on conventional meters or output to RS232C, RS422, or CAN-Bus interfaces.

With a phase-difference detection system, the relationship between cable length and amplitude can be ignored. Therefore, the Inductcoder has very high repeatability. Temperature drift is automatically compensated.

The standard configurations of the Inductcoder include rotary, linear, wire, stroke detection, linear gauge, and strain gauge versions. Regarding performance, an absolute resolution of 1020 can be achieved from an Inductcoder only 10 mm in diameter.

The Inductcoder has been specified for many applications including hydraulic systems, pneumatic systems, and automated semiconductor assembly.

Encoder Technology

Angular sensor with integral motor controller

In production it is essential to minimize machine downtime when changing tools and settings for producing a different product on the same machine. In the packaging and printing industries, for example, these setting tasks are now being increasingly automated and handled by actuators. Conventional actuators consist of a motor, gearbox, and an angle-sensing encoder controlled by a programmable logic controller (PLC) operating with a motor drive circuit and counter. The counter converts the incremental signals from the encoder into position values. Even a simple position control needs this relatively complicated configuration.

As a step towards simplifying this application, Baumer Electric has included the drive electronics and counter with the encoder. The result is the MDB sensor, an angular sensor/actuator that can be directly linked to a PLC. The MDB sensor attaches to the motor in place of the usual encoder. The sensor circuit converts the encoder signals to a form for direct counting by the digital inputs on the PLC. The method uses short-circuit-proof 24V signals arranged such that at a speed of 2,300 rpm the PLC counting routine only needs to interrogate the MDB sensor every 5 milliseconds in order to be sure of not missing a measurement step. This, in turn, minimizes the load on the PLC.

Erich Russ, Marketing Manager at Baumer Electric, points out, "Using the new sensor in the simplified drive design, the separate drive circuit, counter, and wiring are all replaced by the MDB sensor." He estimates that this saves about 40% of the total costs of the actuator system.

Baumer Electric AG

Magnetostrictive sensors for active car suspension

Sensors working on the Temposonics magnetostrictive principle were invented about 30 years ago by MTS Systems Corp. and are now widely used in many different fields. The manufacture of these magnetostrictive linear-position sensors involves a degree of manual assembly, making them too expensive for mass-produced applications. So they are mainly used as industrial sensors, which are typically built to order for a particular application.

Now MTS has developed an automated manufacturing process for its Auto-SE range of Temposonics magnetostrictive sensors. Automation has reduced the cost of this range to a level compatible with the demands of high-volume products. This means that magnetostrictive technology with its inherent high reliability and performance is now very attractive in many high-volume applications. As Jesse Russell, MTS new market development manager, puts it:

"Auto builders can now benefit from this technology and incorporate the Auto-SE to sense shock absorber movement in active suspension systems and many other automotive and non-automotive applications. Here, component reliability and ruggedness is essential to provide the 'fit & forget' performance needed for car manufacture." He adds that the main feature of the development was to produce sensors with many of the critical characteristics of the industrial sensors, but in shorter, fixed lengths and at much lower cost.

The Temposonic magnetostrictive principle involves pulsing current through a wire waveguide. The magnetic field produced by the current interacts with the magnetic field of a permanent magnet attached to the moving part to be measured. This interaction produces a strain pulse in the wire, traveling at the speed of sound in the waveguide alloy. The strain pulse is sensed at the end of the wire. The time between the current pulse and reception of the strain pulse is a measure of the distance to the position magnet on the moving part.

The method is non-contact so there is practically no wear and the strain produced is at a low level that does not fatigue the wire. A number of output formats are available to suit the application. These include a voltage output that varies linearly with length and a pulse-width modulated output.

MTS Systems Corp.

Absolute linear measurement sensor

Glass scales for use in linear measurement are fairly common, but they usually don't offer an absolute measurement. These incremental systems require a reference pass before being put into operation. Now TR-Electronic has developed a glass scale with a chromium structure encoded for absolute measurement lengths up to three meters.

The LT product range operates on the photoelectric principle. A light-emitting diode, acting as the light source, projects light onto the glass scale via a deflection mirror. A row of photoelectric sensors on the other side of the glass scale detects the light pattern produced by the encoding on the scale. For OEM machine integration, an aluminum housing accommodates the glass scale, which is stationary. A slider containing the light source, mirror, and photoelectric detecting array moves along the scale.

Apart from the linear movement in the measurement direction, the combination of track encoding and light projection enables high-resolution information to be extracted about the 3D coordinates as well as angular position of the measurement scale with respect to the detector array. With this additional information, the evaluation system corrects guidance and adjustment errors to produce a specified measurement uncertainty of 0.1 microns. Also, redundant structure information increases immunity from interference.

Uwe Kipping, product manager for LT sensors at TR-Electronic, highlights the advantages of this measurement system: "Using this signaling technique the maximum speed of travel for the LT sensor is about 20 meters per second. With the incremental type of sensors, the evaluation electronics limit the speed due to the requirement of keeping in synchronization. In contrast with this absolute system of encoding, the speed is only limited by the mechanical components."

The LT system uses the Serial Synchronous Protocol as standard, but this can be converted to bus interfaces such as CAN-bus or Profibus. An RS485 serial interface is provided to program the unit and for obtaining special information on system disturbances and the degree of contamination on the glass scale.

TR Electronic GmbH

Miniature interferometer for micro-machining

When ultra-precision is needed in machining at sub-micron levels, complex interferometers are used, incurring high costs per axis and taking up large volumes when integrated on a machine. Although laser-diode interferometers are available which also take advantage of the high resolution, dynamics, and linearity, costs are still significantly high.

IntOp, with their marketing partners Polytec, have now gone one stage further with their miniaturized semiconductor laser interferometer based on a modular design. The measurement system consists of the sensor, driver electronics, PC counter card, and power supply. For low-cost OEM applications, a minimum configuration is available with just the sensor and driver electronics.

The interferometric principle is based on the superimposition of the beam reflected from the measurement object with a reference beam. The resulting interference fringes change with the distance traveled to the object and can be counted. A 2-mm diameter spherical mirror reflects the beam, rendering the instrument insensitive to tilting. The laser beam, which has an effective measurement diameter of only 0.5 mm, is modulated at a frequency of 500 kHz. This means that changes, such as beam intensity, do not affect the 10 nanometer resolution.

A sub-micron grinding spindle is one application for the miniaturized interferometer. The beam passes through a hole in the high-speed spindle leading to the grinding tool. The interferometer controls the position of the tool to which a mirror is attached, reflecting the laser beam back to the instrument. The interferometer control also measures vibrations and axial loads on the spindle, changing the rotational speed or feed rate appropriately. Other applications include wafer and mask alignment, and micro-lithography.

Polytec GmbH

Additional products, capabilities

Intelligent capacitive level monitor

The type KNQ intelligent capacitive level monitor from ifm electronic is used for sensing the levels of liquids and bulk materials. The flat, 10-mm-high design can be simply attached to the sides of pipes or containers. When an inductive button is activated, the integral microcontroller adjusts to the medium and the suppression of the container wall. The inductive button system replaces conventional potentiometers, giving better sealing and improved accessibility where mounting space is restricted. Remote calibration and signaling can also be carried out by a wired connection.

ifm electronic gmbh, +49-201-2422-0.

Pixel-counting sensor

Camera-based sensors can be expensive and difficult to program. Not so with PresencePLUS(TM), a low-cost pixel-counting system. To work, the new sensor captures a 256-level grayscale image of a specified area, converts the image to black and white pixels, counts the pixels, and compares the count to user-programmed threshold values to render a pass/fail judgment. Users program and monitor the PresencePLUS via a handheld, microprocessor-based controller. Programming designates which pixel color to count, White or Black; the auto-exposure time, Indexed or Motion; and the light source behavior, Off or Strobed. Depending on application requirements, PresencePLUS programming is accomplished in one to three steps.

Banner Engineering Corp., +1 612 544 3164.

Compact proximity sensor

Measuring only 10.2 mm high x 16 mm wide x 28 mm deep, the Q10S proximity sensor fits confined areas where standard sensors will not. Despite its small size, the Q10S achieves a 2-mm sensing range with a repeatability of equal to or less than 2% rated operating distance-even when fully embedded in steel. An overmolded, waterproof housing and potted-in 2m pvc-jacketed cable ensures the sensor withstands washdown and harsh environments. Available in three-wire, 10 to 30V dc; two-wire, 20 to 250V ac; and two-wire 5 to 30V dc NAMUR, the Q10S meets DIN 19234 requirements. All versions feature integral circuitry to protect against short-circuit, overload, wire-break, and reverse polarity.

Turck Inc., +1 612 553 7300.

One Touch(TM) Photoelectric family

More than 2 million gates on one 3 x 4 mm chip make the OESII ASIC feature-rich. Incorporated into the W.1000 photoelectric sensor family, the custom ASIC allows:

  • Teach-in ability. One press of the Teach-in button and the sensor automatically sets itself up for the application.

  • Background suppression. The sensor "sees" dark-colored objects directly in front of light-colored objects directly in front of light-colored backgrounds without false readings or adjustment.

  • Stress-free molded lens. Normally, polarizing filters must be placed in front of molded lenses to prevent light distortion. With stress-free molding, the lens goes in front to reduce parts and cost.

For durability, the W.1000 nose is molded as part of the body. ABS plastic and ultrasonic welding result in a one-piece, watertight design. The W.1000 comes in the following ranges: 50-mm background suppression proximity; 100-mm background suppression proximity; 500-mm energetic proximity; 4.2m polarized reflex; 1m fiber optic with through beam fibers; 150-mm fiber optic with proximity fibers; and 10.5m through beam.

Sick, +1 612 941 6780.

GMR test kit

Giant magnetoresistive (GMR) sensors are said to outperform other sensing technologies such as Hall Effect and anisotropic magnetoresistive (AMR). Availability of a specially packaged evaluation kit enables engineers to see for themselves. The kit contains the components necessary to demonstrate the sensor's functions, including four PCBs, two ceramic disc magnets, and two sintered AlNiCo magnets. During operation, the giant magnetoresistive effect changes the electrical resistance when stacked layers of ferromagnetic and non-magnetic materials are exposed to a magnetic field. Applications? Linear or rotary speed detection, linear or rotary position sensing, current sensing, and magnetic field sensing.

Rhopoint Components Ltd., +44 1883 717988.

High-performance accelerometer

For engineers needing to instrument "hot" locations in extremely tight spaces, Model 2248/2248M1 is ideally suited to very high temperature (480C) applications where limited space has eliminated the use of other accelerometers. Of the two versions, Model 2248 incorporates a flange mount with two 4-40 screws; Model 2248M1 includes an integral 10-32 stud mount. A 3m, high-temperature hardline cable assembly is supplied with both models as a standard accessory. The 2248/2248M1 features a charge sensitivity of 3 pC/g with a frequency response from 1 Hz to 8 kHz. This extended frequency response enables the user to perform vibration and shock measurements over a wide bandwidth on structures and components in extremely hot situations. Applications include gas turbine engine casings, high-temperature combustors, diesel exhaust testing, and rocket motor thrusters.

Endevco Corp., +1 949 493 8181.

Level measurement with sonar

The Sonar-BERO sensor from Siemens uses a non-contact ultrasonic beam to detect the level of liquids and granular or powder solids. The measurement is accurate to within 1 mm over a range from 6 cm to 10m. Switching distance can be programmed using the SONPROG software and a switching or analog output can be provided. The sensor can be operated with background suppression where the object to be detected reflects the beam, or in the "window" mode where a passing object interrupts the beam which is preset to a defined background.

Siemens, +49 9131 7 25292.

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