Scale with weight-to-period transducer
First Claim
1. A scale comprising a frame, load carrying means for carrying an article to be weighed, transducer means, means fixedly supporting the transducer means with respect to the frame, force transmitting means interconnecting the load carrying means and the transducer means, means actuating the transducer means to provide an oscillatory signal, the period of oscillation of which varies as a function of the weight of the load and means receiving the oscillatory signal and generating a period signal indicative of full cycles of oscillation of the oscillatory signal and in response thereto measuring the duration of its period of oscillation to provide an article weight signal.
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Abstract
A postage scale includes a directly loaded weight-to-period transducer which provides an oscillating output, the period of which varies as a function of the weight to be measured. The transducer includes a disc of piezoelectrically active material bonded to an inactive substrate base which dishes at its center in response to the weight to be measured. The transducer frequency output is processed to provide a digital period signal. A reference oscillator having matched temperature characteristics generates a high frequency count calibrated for scaling the transducer period to a weight count. The high frequency signal and the period signal are gated to provide an input to a counter which generates a digital weight information signal. The weight information signal is transmitted to a mailing system processor for use in determining the postage requisite for mailing the article.
18 Citations
9 Claims
- 1. A scale comprising a frame, load carrying means for carrying an article to be weighed, transducer means, means fixedly supporting the transducer means with respect to the frame, force transmitting means interconnecting the load carrying means and the transducer means, means actuating the transducer means to provide an oscillatory signal, the period of oscillation of which varies as a function of the weight of the load and means receiving the oscillatory signal and generating a period signal indicative of full cycles of oscillation of the oscillatory signal and in response thereto measuring the duration of its period of oscillation to provide an article weight signal.
- 8. A postal scale suitable for automated mail processing applications, the scale comprising a pan adapted to carry an article being weighed, a disc shaped piezoelectric transducer, means supporting the transducer adjacent the periphery thereof, means for applying the weight of the article to an unsupported area of the transducer, means electrically driving the transducer, the transducer providing an oscillatory signal in response to the driving means, means receiving the oscillatory signal and providing a square waveform signal in response thereto, means receiving the square waveform signal and in response thereto providing a period signal indicative of the period of oscillation of the oscillatory signal and means receiving the period signal and in response thereto providing an article weight signal.
Specification