摘要:
A proximity detector includes an offset circuit for bringing at least one of a magnetic field signal and a tracking signal towards the other one of the magnetic field signal and the tracking signal when the detector output signal changes state. A magnetic field-to-voltage transducer provides the magnetic field signal indicative of an ambient magnetic field and a peak detector responsive to the magnetic field signal provides the tracking signal which substantially follows the magnetic field signal. A comparator generates the detector output signal which changes state when the magnetic field signal varies from the tracking signal by a predetermined amount.
摘要:
A magnetic-field-to-voltage transducer includes a Hall element and a digitally gain-controlled Hall-voltage amplifier that produces an analog voltage Vsig having excursions of one polarity corresponding to the passing of magnetic articles. Vsig is applied to the input of a signal-manipulating circuit that generates a proximity- detector binary output voltage, Vout, having transitions of one direction each time a predetermined point is reached in Vsig. A digitally gain-controlled gain amplifier is connected to the Hall element. A comparator circuit generates a binary signal Vbig (or V.sub.toobig) that changes from one to another binary level each time that Vsig exceeds a DC target voltage, V.sub.TG. The AGC circuit senses and counts gain counter excursions of one polarity in Vsig, and produces a binary count output signal at the input of the gain amplifier at each of the counted excursions in Vsig, incrementally changing the transducer gain in the direction to bring the peaks in Vsig to just below the target value T.sub.TG. This AGC feature prevents saturating the amplifier and quickly renders a Vsig of essentially constant amplitude so that either the peak excursion values or predetermined threshold levels in Vsig, at which transitions in the proximity detector output voltage Vout are caused to occur, provide greater accuracy and stability in the correlation between detection-approach and -withdrawal distances and transitions in Vout.
摘要:
A proximity detector for sensing a magnetic field includes a magnetic-field-to-voltage transducer for generating a signal voltage Vsig that is proportional to the magnetic field, a peak-to-peak percentage threshold detector coupled to the magnetic-field-to-voltage transducer to receive the signal voltage Vsig and for providing an output signal voltage Vout and a forcing circuit coupled to the peak-to-peak percentage threshold detector for forcing and maintaining the value of the output signal voltage Vout at a predetermined value during an initial startup interval of the proximity detector. The proximity detector may further include an automatic gain control circuit coupled to the forcing circuit to provide a proximity detector capable of operating in a peak-to-peak percentage threshold detector mode with automatic gain control.
摘要:
A magnetic-field-to-voltage transducer includes a Hall element and a digitally gain-controlled Hall-voltage amplifier that produces an analog voltage Vsig having excursions of one polarity corresponding to the passing of magnetic articles. Vsig is applied to the input of a peak-referenced-threshold signal detector that generates a binary proximity-detector output voltage, Vout, having transitions of one direction upon approaches of gear teeth down to zero speed. A digitally gain-controlled amplifier is connected to the Hall element. A comparator circuit generates a binary signal Vbig (or Vtoobig) that changes from one to another binary level each time that Vsig exceeds a DC target voltage, VTG. The AGC circuit incrementally changes the transducer gain in the direction to bring the peaks in Vsig to just below the target value TTG. Reference voltages VP2 and VN2 are generated that are equal respectively to the most recent peak positive and negative going excursion in Vsig. DC off-set-limit voltages VA and VB are provided that are respectively above and below the center of the dynamic voltage range of the detector, and the entire signal Vsig at the output of the amplifier is biased in a negative direction when the median value, Vos, of Vsig is greater than VA and moving the entire signal Vsig in a less positive direction when Vos is less than VB to keep Vos within the range from VB to VA.
摘要:
A method for detection of passing magnetic articles which includes an initial step of sensing an ambient magnetic field and generating a voltage, Vsig, proportional to the magnetic field. A threshold voltage is generated as a percentage of the peak-to-peak voltage of Vsig. The method further includes the step of generating a proximity detector output voltage that becomes one binary level when Vsig rises to exceed the threshold voltage and another binary level when Vsig falls to below the threshold voltage. The threshold voltage is periodically updated to remain the percentage, within a predetermined tolerance, of the peak-to-peak voltage of Vsig in response to changes that may occur in the peak voltages of Vsig. In one embodiment, the threshold voltage is at a first level corresponding to a first percentage of the peak-to-peak voltage of Vsig when Vsig exceeds the threshold voltage and is at a second level corresponding to a second percentage of the peak-to-peak voltage of Vsig when Vsig is less than the threshold voltage.
摘要:
A Hall transducer produces a signal Vsig. Threshold voltages V.sub.Pth and V.sub.Nth are generated at the beginning, t.sub.update, of each of a succession of update time intervals, of 64 pulses in Vsig, to be fixed percentages respectively of the peak to peak voltage in Vsig. A proximity-detector binary output voltage is high when Vsig exceeds threshold voltage V.sub.Pth and low when Vsig is below threshold voltage V.sub.Nth. Signals V.sub.Pold and V.sub.Nold, generated by first and second DACs, are equal to the first positive and negative peaks in Vsig after each time t.sub.update initiating the start of a successive interval. Signals V.sub.Pnew and V.sub.Nnew, simultaneously generated by third and fourth DACs, are equal to the greatest positive and negative peak voltages in Vsig during the interval ending at t.sub.update. Counters present their count to the first and second DACs that count pulses from a clock for tracking and holding +/- peaks in Vsig. After each time t.sub.update, a pulse in a signal Vupdt is generated if at time t.sub.update V.sub.Nnew lies outside the range. V.sub.Nold -v to V.sub.Nold +v of if V.sub.Nnew lies outside the range V.sub.Nold -v to V.sub.Nold +v, where v is an incremental DC bias voltage. Vupdt resets the counters so that during the succeeding update time interval the threshold voltages V.sub.Pth and V.sub.Nth have the fixed percentages of the updated threshold voltages V.sub.Pnew -V.sub.Nnew.
摘要翻译:霍尔传感器产生信号Vsig。 阈值电压VPth和VNth在Vsig中的64个脉冲的连续更新时间间隔的每一个的开始时产生,分别为Vsig中峰峰值电压的固定百分比。 当Vsig超过阈值电压VPth时,接近检测器二进制输出电压为高电平,当Vsig低于阈值电压VNth时,接近检测器二进制输出电压为高电平。 由第一和第二DAC产生的信号VPold和VNold等于每次启动连续间隔开始后的Vsig中的第一个正和负峰值。 由第三和第四DAC同时产生的信号VPnew和VNnew等于在tupdate结束的间隔期间的Vsig中最大的正和负峰值电压。 计数器将其计数器显示给第一和第二DAC,它们计数来自时钟的脉冲,用于跟踪Vsig中的+/-峰。 在每次tupdate之后,如果在tupdate VNnew处于该范围之外,则产生信号Vupdt中的脉冲。 如果VNnew位于VNold- + Z v到VNold ++ Z v的范围之外,则VNold- + Z v至VNold ++ Z v,其中+ Z v是增量DC偏置电压。 Vupdt复位计数器,使得在成功更新时间间隔期间,阈值电压VPth和VNth具有更新的阈值电压VPnew-VNnew的固定百分比。
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.
摘要:
Apparatus for detecting a passing magnetic article includes a peak detector providing a detector output signal that changes state when the magnetic field signal differs from a magnetic field tracking signal by more than a threshold offset amount. The threshold offset amount is dynamically variable in response to detection of a speed of rotation of the magnetic article and a peak-to-peak signal level of the magnetic field signal.
摘要:
An apparatus and a method provide an output signal indicative of a speed of rotation and a direction of rotation of a ferromagnetic object capable of rotating. A variety of signal formats of the output signal are described.
摘要:
Apparatus for detecting a passing magnetic article includes a peak detector providing a detector output signal that changes state when the magnetic field signal differs from a magnetic field tracking signal by more than a threshold offset amount. The threshold offset amount is dynamically variable in response to detection of a speed of rotation of the magnetic article and a peak-to-peak signal level of the magnetic field signal.