bullet Sensors & Transducers e-Digest (S&TD)

 


 

No. 10, October 2002

 

Bullet

Table of Contents

 

 

PRODUCTS

 

Miniature, High Sensitivity Piezoresistive Pressure Transducer

 

The Model 8507C is designed for installations that do not require threaded mounting, or locations that are difficult to reach. Its small size (0.092-inch cylindrical case) permits flush mounting on curved surfaces. This miniature, high sensitivity piezoresistive pressure transducer is available in ranges from 1 psi to 15 psi, with full scale output up to 300 mV. The Model 8507C provides excellent performance and stability during temperature transients, using self-contained hybrid temperature compensation. It also offers excellent linearity (up to 3X range) and high shock resistance (up to 10,000g's). The Model 8507C's active four-arm strain gage bridge is diffused into a sculptured silicon diaphragm for maximum sensitivity and wideband frequency response. This high sensitivity, combined with small size, makes the transducer ideal for use on small-scale models in wind tunnels.

 

30700 Rancho Viejo Road

San Juan Capistrano

California 92675

tel: (949) 493-8181

fax: (949) 661-7231

http://www.endevco.com

Pressure Transducer 850C

 

 

High Resonance Frequency and Zero Damping Piezoresistive Accelerometer

 

Endevco's Model 7270A is a rugged, un-damped piezoresistive accelerometer designed for shock measurements. Its low mass, extremely small size and unique construction provide multiple benefits, including exceptionally high resonance frequency, low impedance, high overrange, and zero damping for no phase shift. The Model 7270A's high resonance frequency allows it to survive a shock pulse that could shatter the seismic system of accelerometers having lower resonance. With the addition of zero damping, it can respond accurately to shock motion characterized by a fast rise time and short duration. The Model 7270A's frequency response extends down to DC or steady state accelerations, making it ideal for measurement of long duration transients. Full scale range is +2000 to +200,000 g's.

 

The sensing system of the 7270A is micro-machined from a single piece of silicon. This etched silicon chip has the inertial mass and strain gages arranged in an active four-arm Wheatstone bridge circuit, complete with an on-chip zero balance network.

 

Endevco,

30700 Rancho Viejo Road

San Juan Capistrano

California 92675

tel: (949) 493-8181

fax: (949) 661-7231

http://www.endevco.com

Piezoresistive Accelerometer 7270A

 

 

Rack-Mountable Signal Conditioner for Centralized Control of Multiple Units

 

Endevco's new Model 2775B signal conditioner is rack-mountable, fitting from one to six units in a 19-inch enclosure. This product is a significant upgrade for vibration laboratories worldwide, allowing centralized control of up to 20 units per COMM port via a RS-232 computer interface. Additional COMM port expanders can significantly multiply the number of units into the hundreds, all manageable from one computer. Significant features of the Model 2775B include: the widest dynamic range from 0.01 to 100,000 engineering units; front panel manual control or computer control via RS-232 Windows®-based software; broad sensor input sensitivity range (0.0001 to 10,000 mV/EU or pC/EU); a gain from 1 to 10,000; switchable isolation; and a front panel analog meter. In addition, a wide-input universal power source accepts 90 to 240 VAC/50 to 400Hz.

 

This signal conditioner provides three standard outputs: (1) AC output voltage proportional to input, (2) DC output voltage proportional to input, and (3) a servo output (five selectable levels) that provides a constant voltage, typically used in servo or shaker control loops or systems. AC and DC outputs are programmable from 1 to 10 volts. Options that are available to support the Model 2775B include: Model 35771 4-pole Butterworth plug-in filter that is jumper configurable for high-pass, low-pass or band-pass filtering. Model 35818 Filter Integrator Module providing velocity and displacement scaling of the input vibration signal. Model 35933A Application Software that provides an RS-232 computer interface for Windows-based configurations at up to 20 channels per COMM port. Model 4948A six-slot rack. The aluminum-encased 2775B weighs approximately four pounds and measures 5.0 x 2.78 x 13 inches as a standalone configuration.

 

Endevco,

Tel: (949) 493-8181

fax: (949) 661-7231

http://www.endevco.com

2775B Signal Conditioner

 

 

Hopkinson Bar Shock Calibration Services Now Available from Endevco

 

SAN JUAN CAPISTRANO, Calif. - October 1, 2002 - Endevco now offers calibration services based upon the Hopkinson Bar. Endevco's Model 2973A Shock Motion Accelerometer Calibrator (SMAC™) will be used to perform controlled shock excitation for sensitivity calibration of accelerometers from 10,000 g's to +100,000 g's. The Model 2973A provides precise, repeatable control of drive momentum by controlling pressure with a voltage-to-pressure regulator and releasing it with an electrically-operated poppet valve. It also eliminates the need for paper diaphragms and features a simpler, more reliable bar suspension system.

 

Driven with pressurized air, a projectile with a shaped tip impacts a deformable aluminum mitigator on one end of the bar, generating a compression wave in the bar that imparts an acceleration to a test transducer mounted on the opposite end. Strain gages on the bar measure the compression wave. The relation between the strain rate and the acceleration is the basis of the calibration. Depending on the version of the Hopkinson bar ordered, the test accelerometer can be mounted directly to the bar or onto a breakaway fixture which flies free from the bar after the shock pulse. The use of the breakaway eliminates repeated exposures of the test transducer to reflections of the compression wave, and allows zero shift measurements. The system can be used either manually, as a standalone device, or in an automated mode.

 

Endevco,

Tel: (949) 493-8181

fax: (949) 661-7231

http://www.endevco.com

Model 2973A Accelerometer Calibrator

 

 

HMC1055 Chip Set with the Elements to Design a Three-Axis Magnetic Compass

 

Honeywell introduced the HMC1055, the first in a new series of three-axis magnetic sensor products made for the compass designer. The HMC1055 3-Axis Compass Sensor Set includes Honeywell's magnetic sensors, the HMC1051Z, HMC1052, and a dual-axis accelerometer to be used as a tilt sensor. These products make up the five axes of measurement (X, Y, and Z-axis headings; plus pitch and roll) which provides the sensing elements needed to make an electronically gimbaled compass.This chip set allows users to design their own tilt-compensated compass solutions. It ships with a datasheet including application notes for reference compass design, with pinouts and footprints of the sensors for a compass circuit implementation.

 

Honeywell established an alliance with MEMSIC, Inc. N. Andover, MA to supply their two-axis accelerometer, as a cost effective method of sensing tilt. It is supplied in a miniature LCC-8 package (5mm x 5mm x 2mm), and uses a thermal means of sensing pitch and roll accurately up to ± 60° without moving parts. Honeywell's HMC1051Z and HMC1052 are high performance Anisotropic Magneto-Resistive (AMR) sensors designed for small spaces.The HMC1052 offers perfectly orthogonal two-axis sensing, ultra small size and low power capability in a miniature surface mount package. The HMC1051Z uses the same technology as the HMC1052, but is conveniently packaged in a 8-pin SIP format to provide a vertical oriented sensor, thus requiring no extra daughterboard for the Z-Axis sensor orientation.

 

The resulting HMC1055 chip set is an easy to use, cost effective solution for the compass system design engineer who needs three-axis compass sensing for the product application; but wants a "head start" using the reference design and proven sensors. Honeywell's complete family of magnetic sensor-based products offer high sensitivity for accurate compassing, remote vehicle detection monitoring, virtual reality, position sensing, security systems and medical instrumentation.

 

Connie Krauth

Honeywell Defense and Space Systems

Tel: (612) 951-5328

Http://www.magneticsensors.com

 

 

The World’s First Programmable Hall Sensor

 

Micronas, the world’s leading supplier of hall sensors and a leading supplier of IC solutions for multimedia, consumer and automotive electronics today announced the world’s first programmable hall sensor able to linearize magnetic fields measured by the sensor element. With the HAL 855, automotive system manufacturers effectively only have to store the typical output characteristics for each application (e.g. fuel tank gauges) into the on-chip EEPROM (end of line programming). The overall functionality of the HAL 855 allows the customers to replace various conventional potentiometers. It is well positioned for the detection of positions and angles in vehicles and industrial applications.

 

The HAL 855 has an integrated EEPROM with higher memory capacity and additional logic circuitry for the computation of a range of output characteristics,” commented Peter Zimmermann, automotive market manager at Micronas. “Currently, no other hall sensor on the market offers sufficient on-chip memory capacity and digital signal processing power to perform the linearization, and a purely analog approach will not solve the problem”.

 

Since the chip is programmed only at the end of the production line, it is not necessary to support many different types of potentiometers. This makes the inventory handling much easier and reduces inventory and logistic costs dramatically. "I believe that 10 percent of inventory costs can be saved by using the new programmable hall sensors compared to conventional electro-mechanic potentiometers” added Zimmermann.

 

Hall sensors offer one other significant advantage. Potentiometers measure data by making contact with the content surface and are therefore prone to wear and tear and serious corrosion. Hall sensors, however, measure the magnetic field contactless so external influences such as dirt, vibration and abrasion do not distort the measurement results. This allows the delivery of highly accurate and reliable measurement data over the entire product life cycle.

 

On-chip DSP circuitry does all the computing required to digitize the magnetic field and translates it according to the data stored in the EEPROM into the non-linear output data and vice versa.. One example for this kind of applications are low-cost magnetic circuits (e.g. ferrites), which offer only a limited range of linearity. The HAL 855 compensates this non-linear behavior allowing mapping at an angular range of +/- 45°, a significant improvement over +/- 30° when using simple low cost magnetic circuits.

 

Typical application: Fuel indicators.

 

Nearly every type of car has a proprietary tank. To enable the dashboard fuel indicator to show the fuel content, system manufacturers have traditionally deployed potentiometers, which have been tailored to every different tank type. Each potentiometer type is not only expensive to develop but also expensive for inventory handling and logistics.

 

Inaccurate and misleading tank indicators are a source of many car driversґ complaints. Failures may occur for example when potentiometers are mixed up during production: if a potentiometer type is built in which does not fit the specific tank form, it delivers wrong measurement data. An additional source of misleading data is wear: the wiper contacts are unreliable over time and even if the linearizing is done by the dashboard controller the disadvantages of the wiper contacts remain. “With the smart hall sensor we can do all the required measurements and data processing at the very location inside the tank. Since the system manufacturers can program the specific characteristic curves at the end of their production line, they eliminate additional logistic costs and failures due to permutated potentiometers and can achieve a much higher level of accuracy and reliability”, says Peter Zimmermann.

 

The HAL 855 operates at temperatures between -40°C and +150° C (crystal temperature). Samples are available now. In high volumes the HAL 855 sells at a price of $ 1.50.

Micronas

http://www.micronas.com

 

 

 

 

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