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Electronic Design


Digital Resistors Measure And Compensate For Thermal Variations
The DS1847 and DS1848 dual temperature-controlled NV variable resistors automatically measure and compensate for thermal variations affecting laser behavior in optical transceivers. According to the company, these devices are suited to aid designers achieve precision and safety in laser activity.

Both devices integrate dual, 256-position, linear taper resistors with a digital thermometer and EEPROM. The DS-1848 has an additional 128 bytes of general-purpose EEPROM. These resistors eliminate the need for external temperature checks or manual compensation in high-speed transceivers. Once installed, they automatically adjust current according to temperature changes.

The designer determines design-specific resistance characteristics at temperature intervals of 2°C and stores the data in on-chip EEPROM. In operation, both devices measure temperature and check readings against an EEPROM lookup table, adjusting resistance accordingly. All thermal data and control instructions are communicated over an industry-standard, two-wire interface. Both may operate with 3- or 5-V supplies over a temperature range of −40°C to 95°C.

Both variable resistors are available in 14-pin TSSOP or die-sized, flip-chip packages. In 1000-unit quantities, the DS1847 and DS1848 cost $2.29 and $2.57, respectively.

Dallas Semiconductor, 4401 South Bellwood Pkwy., Dallas, TX 75244-3292; (972) 371-3719;

Sensor Is Fitted For Use In Noncontinuous-Flow Operations
This "line fill" flow sensor suits applications where the absence of tanks or the use of disposable reservoirs precludes the fitting of conventional fluid-level sensors. In medical dosage devices, water pumping systems, garden fountains, and similar liquid dispensing equipment, the sensor may be fitted in the delivery pipe to sense liquid in noncontinuous flow operations.

The sensor indicates when a liquid reservoir needs filling or replacing through connection to an external visual or audible warning device. It fits applications where liquid delivery has pressure pulses or where the delivery line is intermittently fed from a pump source. Features include UL-listed materials, with ABS housing and polypropylene float. The sensor provides maximum switching of 100 V dc at 1 A and 15 W. A maximum operating pressure of 1 bar is also provided.

Connections accommodate a 3-mm diameter push-on hose, and a one-way valve is fitted to prevent "suck back."

For pricing and availability information, contact the company.

Gentech International Ltd., Grangestone Industrial Estate, Girvan, Ayrshire KA26 9PS, U.K.; +44 (0) 1465-713581; Internet:

Capacitive Sensors Can Withstand Temperatures From 200°C To 250°C
Models in a recent line of high-temperature capacitive sensors can withstand temperatures from −200°C to 250°C. Available in 18- and 30-mm diameters, the devices have stainless-steel bodies and an adjustable operating distance of 5 to 15 mm.

Cable lengths of 2 or 5 m are available to connect the amplifier. The amplifier is supplied either through one-sensor connection with the option of delay sensing or two-sensor connection. According to the company, these sensors are suited to control levels of hot materials such as liquids, oils, powder, and plastic granules. They also sense solid metallic and nonmetallic bodies positioned in areas of high temperature.

Available now, pricing for the sensor starts at $200 each. Pricing for the amplifier starts at $250.

Fargo Controls Inc., P.O. Box 539, Eatontown, NJ 07724; (800) 241-3755; fax (732) 542-3553;

Industrial Accelerometer Measures Under One Inch
The 785A low-profile industrial accelerometer measures under one inch. It features a 316L stainless-steel, hermetically sealed case that is corrosion resistant and ground isolated.

This accelerometer has ESD, RFI, and reverse wiring protections. Weighing only 85 g, it offers a temperature range of 50°C to 120°C and a vibration limit of 500 g. Other specifications include a sensitivity of 100 mV/g (±10%), an 80-g peak acceleration range, 1% amplitude nonlinearity, and frequency response of 2.0 to 8000 Hz (±10%) and 1.0 to 12,000 Hz (±3dB). According to the company, the device is suited for use in conveyors, drives, or any industrial situation involving a height constraint and the need for vibration monitoring.

The 785A has a standard 2-pin MIL-C-5105-style output connector. An R6-type mating connector is also available.

Contact the company for pricing and availability information.

Wilcoxon Research, 21 Firstfield Rd., Gaithersburg, MD 20878; (800) WILCOXON; fax (301) 330-8873;

Laser Sensor Line Has Visible Red Source With Class 1 Emission Rating
The 18K series of laser position sensors offers a Class 1 rating per EN 60825-1, ensuring safety in all applications. The 18-mm tubular sensors use a 650-nm red laser and are available in all popular sensing modes, including retroflective and thru-beam.

High-speed applications such as assembly and packaging lines can be accommodated by the lasers' response time of 333 µs and switching frequency of 1.5 kHz. Diffuse versions have a range of 300 mm and resolution up to 0.5 mm for applications requiring high accuracy at short sensing distances. Polarized retroflective versions are available with a range of 12 m and resolution to 1 mm for longer-range applications. Also, thru-beam versions extend the range to 50 m with resolution to 2.5 mm.

These CE-rated lasers operate on 10- to 30-V dc supplies and are protected against short circuits and reverse polarity. Their ABS plastic housings are sealed to IP67 and are available with a four-pole M12 connector. Status LEDs confirm output function and signal stability to speed setup.

For pricing and availability of the 18K line, contact the company.

Baluff Inc., 8125 Holton Dr., Florence, KY 41042; (800) 543-8390;

Linear Image Sensor Is Geared To Large Pixel Applications
The Enhanced Linear Imager Sensor (ELIS) is geared to lower-cost, large pixel applications. The device features low noise, low dark current pixels, dynamic range, and high sensitivity. According to the company, it is suited for applications such as barcode reading, contact scanning, laser triangulation, position displacement, and spectroscopy.

The device uses Active Column Sensor (ACS) technology in which the video signal generated at the pixel site remains intact and at full strength. In this way, fixed pattern noise (FPN) is virtually eliminated. The device features 7.8- by 125-µm pixels and an active area of 7.98 mm by 125 µm. Users can combine two, four, or eight adjacent pixels together to act as a single pixel. Binnable resolutions include 128, 256, 512, and 1024 pixels. The bin skip feature maintains the timing relationship between the video and clock.

Other features include an 80-dB dynamic range and a single 2.8- to 5-V dc power supply. On-chip integration of the necessary timing control is standard. The device requires a single CMOS TTL level clock for minimum operation. A sample and hold circuit accommodates strobed or pulsed applications.

Packaging options include PHOTO-SURF (surface-mount), PHOTO-DIP (through-hole), chip scale, and die form. Available in volume quantities in January, the ELIS costs $5.10 to $12.00 each depending on volume.

Photon Vision Systems LLC, P.O. Box 509, Cortland, NY 13045; (607) 756-5200; fax (607) 756-5319;

Pressure Transducers Offer A 4- To 20-mA Output
The PC-304 high-performance pressure transducers offer an accuracy of ±25% from best-fit straight line, including the effects of nonlinearity, hysteresis, and repeatability. The devices feature VIM-CAR construction for corrosion resistance with less than 3 Ra of surface finish on all wetted surfaces.

The transducers are designed to have a conventional two-wire, 4- to 20-mA output. Pressure ranges include 0 to 6 through 3000 psig and 0 to 15, 25, and 50 psia. The devices are available in a wide range of mounting, fitting, and thread configurations to suit specific applications.

For pricing and availability information, contact the company.

Pureron U.S.A. Inc., 19355 Business Center Dr., Northridge, CA 91324; (818) 775-0381; fax (818) 772-2477;

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