That's what Positek Ltd. has done with its series of long- and
short-stroke linear induction position sensors (LIPS). Mounted in the sensor
itself, the electronic interface allows oscillation frequencies of up to 2 Mhz.
Traditionally, high-performance inductive position sensors call for coils with many turns of fine copper wire, leading to relatively bulky designs. Such low-frequency designs also require highly-permeable, high-cost target materials, such as nickel- and silicon-iron. Conversely, less bulky coils with lower turn count resonate at high frequency and can use thicker wire. The reduced time period between oscillations, however, makes synchronous demodulation difficult to achieve.
LIPS locks synchronous demodulation to the signal via custom IC, eliminating the potential for measurement errors. This, in turn, allows high-frequency oscillation. Benefits not only include smaller coils and printed circuit techniques, but low-cost target materials like aluminum and stainless steel. "Performance is midway between an encoder and a potentiometer," says John Francis, Positek director. "LIPS durability puts it miles ahead of the pot in life cost, despite being a bit more expensive to start with," he adds.
While encoders offer high accuracy, Francis says LIPS has the advantage of being an absolute device: "Unlike an incremental encoder, a reading is available at switch-on with virtually infinite resolution," he says.
The new design also makes the sensor particularly suitable for use in areas with high magnetic fields. Rotary versions have been developed using similar principles.
John Francis, Positek Ltd., Queen St., Chedworth, Gloucester UK, GL54 4AG, Tel/Fax: +44 1285 720489.
Replicate the sense of smell
Unlike light or sound, the sense of smell is a chemical process with no scale against which the intensity of an odor can be measured. Established methods of measuring smell involve human inspectors or gas chromatography/mass spectrometry. The latter is slow and complex-more suited for a laboratory test than production process-while the former is inconsistent.
Now, researchers at the University of Manchester Institute of Science and Technology (UMIST) have identified a number of conducting polymers that can be used as transducers for selected individual or mixed chemicals. This development work has led to a commercial system made by AromaScan.
"When interacting with volatile chemicals at room temperature, polymers require only microwatts of power, and can be correlated to specific compounds," says K.C. Persaud, who heads the development team at UMIST. He describes the new product's operation as follows:
The instrument draws chemical volatiles from a sample over an array of 32 polymer sensors, each synthesized to be specific to particular classes of compounds. In the process of absorbing the volatiles, the surface of the sensor undergoes a change in electrical resistance.
Signals from all the transducers generate instantaneous data sets, visualized as bar charts. Processing through a neural network permits recognizing aroma patterns and labeling them against standard patterns.
Chris Tullett, AromaScan plc, Electra House, Electra Way, Crewe, Staffs, UK, CW1 1WZ, Tel: +44 1270 216444, Fax: +44 1270 216030.
Interconnect smart sensors
Smart sensors send packets of information rather than mere data. A web of smart sensors, connected to a PC or PLC through a single bus line,