| 摘要 |
The transducer includes a base plate (8) and a ring (12) carrying crystals with a curved surface. The curved surface is covered by an elastomer film (13) which ensures mechanical stability and covers the gap (14) between the ring and base plate. The bottom side of the transducer (1) is applied to the pregnant woman's abdomen in a position between the optimum positions for fetal heart rate and toco. The curved surface guarantees a good contact to the skin. The plate senses mechanical motion of the abdomen and transmits it to a resistive wire strain component (5) via the guide plate to give an indication of uterus activity. Piezoelectric crystals (10a to 10c and 11a,11b) set up a wide-beam ultrasonic field, and the reflected ultrasonic waves are used to determine the fetal heart rate using an autocorrelation filter. The ultrasonic field generated by the piezo-electric crystals is homogenous even if the base plate is moving.
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