| 摘要 |
A sensing apparatus includes a pulse recirculating circuit operatively connected to at least one ultrasonic delay sensor or other device for recirculating pulses therethrough, and a measurement difference output circuit for generating an output signal based upon a difference between first and second measurements of the at least one ultrasonic delay sensor. The pulse recirculating circuit preferably comprises a pulse generator for generating a series of input pulses to the ultrasonic delay sensor, and a pulse detector for detecting a series of output pulses after propagation through the ultrasonic delay sensor. Moreover, the measurement difference output circuit preferably includes an up-down counter for counting pulses during the first measurement in one direction and for counting pulses during the second measurement in an opposite direction. Accordingly, the remaining counter contents represent a difference in delay between the first and second measurements. Method aspects of the invention are also disclosed.
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