发明授权
US6100680A Detecting the passing of magnetic articles using a transducer-signal
detector having a switchable dual-mode threshold
失效
使用具有可切换双模式阈值的换能器信号检测器检测磁性制品的通过
- 专利标题: Detecting the passing of magnetic articles using a transducer-signal detector having a switchable dual-mode threshold
- 专利标题(中): 使用具有可切换双模式阈值的换能器信号检测器检测磁性制品的通过
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申请号: US851402申请日: 1997-05-05
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公开(公告)号: US6100680A公开(公告)日: 2000-08-08
- 发明人: Ravi Vig , Jay M. Towne , P. Karl Scheller
- 申请人: Ravi Vig , Jay M. Towne , P. Karl Scheller
- 申请人地址: MA Worcester
- 专利权人: Allegro Microsystems, Inc.
- 当前专利权人: Allegro Microsystems, Inc.
- 当前专利权人地址: MA Worcester
- 主分类号: G01B7/00
- IPC分类号: G01B7/00 ; G01D3/02 ; G01D5/14 ; G01D5/244 ; G01D5/245 ; G01V3/08 ; H03K17/95 ; H03M1/30 ; G01P3/488 ; G01P3/489 ; H03K5/08 ; H03K5/153
摘要:
A magnetic-field-to-voltage transducer includes a Hall element and a digitally gain-controlled Hall-voltage amplifier that produces an analog signal voltage Vsig having excursions of one polarity corresponding to the passing of magnetic articles. The gain of an AGC Vsig amplifier is only decreased in small sequential gain increments during an initial interval defined as that in which two excursions in Vsig have occurred, and the gain remains unchanged thereafter. Vsig is applied to the input of a peak-referenced-threshold signal detector that generates a binary output voltage, Vout, having transitions of one direction and the other direction corresponding respectively to the approach and retreat of the passing articles. The peak-referenced-threshold signal detector includes a dual-threshold-voltage comparator which is set to a large threshold at start-up. When just after start-up an excursion in the signal Vsig at the output of the amplifier exceeds a predetermined reference voltage, a small threshold obtains. Such an automatic threshold adjustment is made only in a brief initial period following start-up and not again until the proximity detector has been powered down and then started up again. This automatic dual-mode threshold feature prevents false detection due to "overshoots" that may be present in the transducer signal when the air gap is small, and leads to accurate detection over a wide range of air gaps between the transducer and the passing magnetic articles.
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