GB2334636A - Dynamic range control for a threshold detector - Google Patents
Dynamic range control for a threshold detector Download PDFInfo
- Publication number
- GB2334636A GB2334636A GB9803640A GB9803640A GB2334636A GB 2334636 A GB2334636 A GB 2334636A GB 9803640 A GB9803640 A GB 9803640A GB 9803640 A GB9803640 A GB 9803640A GB 2334636 A GB2334636 A GB 2334636A
- Authority
- GB
- United Kingdom
- Prior art keywords
- signal processing
- output
- variable gain
- amplifier
- processing apparatus
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
- G01D5/244—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
- G01D5/24471—Error correction
- G01D5/2448—Correction of gain, threshold, offset or phase control
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
- F02P7/00—Arrangements of distributors, circuit-makers or -breakers, e.g. of distributor and circuit-breaker combinations or pick-up devices
- F02P7/06—Arrangements of distributors, circuit-makers or -breakers, e.g. of distributor and circuit-breaker combinations or pick-up devices of circuit-makers or -breakers, or pick-up devices adapted to sense particular points of the timing cycle
- F02P7/067—Electromagnetic pick-up devices, e.g. providing induced current in a coil
- F02P7/0675—Electromagnetic pick-up devices, e.g. providing induced current in a coil with variable reluctance, e.g. depending on the shape of a tooth
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/30—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring angles or tapers; for testing the alignment of axes
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
- G01P3/42—Devices characterised by the use of electric or magnetic means
- G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
- G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
- G01P3/4802—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage by using electronic circuits in general
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
- G01P3/42—Devices characterised by the use of electric or magnetic means
- G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
- G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
- G01P3/481—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals
- G01P3/488—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals delivered by variable reluctance detectors
Abstract
An arrangement comprises a threshold detector for pulsiform signals preceded by a gain/attenuation control section so that the input to the threshold detector is always within its dynamic range. Use in a variable reluctance sensor for engine speed and crankshaft angle detection is described.
Description
SIGNAL PROCESSING CIRCUIT
The present invention relates to a signal processing circuit, and in particular to a processing circuit suitable for use with variable reluctance sensors.
Variable reluctance sensors are widely used in automotive applications to sense engine speed and crank shaft angle by detecting the passage of teeth or slots on a rotating ferrous wheel.
The variable reluctance sensor responds to changes in magnetic flux and generates an output voltage in response thereto.
The voltage output of the variable reluctance sensor is a function of the following factors:
1. peripheral speed of the ferrous wheel, 2. the size of the air r gap between the sensor and the ferrous wheel, 3. the size and shape of the teeth or slots, and 4. electrical loading.
Furthermore variations can Occur over one revolution if'hn-out" is present and irregularly sized teeth or slots, or missing teeth, are used for positional identification (eg to find TDC of the first cylinder).
These various factors result in the output voltage of the variable reluctance sensor varying between a few hundred millivolts to a few volts at engine cranking speeds, and from tens of volts up to nearly 100 volts at high speed. A suitable signal processing circuit is required to cope with the large dynamic range which is encountered.
According to a first aspect of the present invention, there is provided a signal processing circuit comprising a variable gain blocks means for controlling the variable gain block and a threshold crossing detector.
Preferably the variable gain block is a variable gain amplifier. Advantageously the variable gain amplifier is a transconductance amplifier. A tIansconductance amplifier is, in effect, a two quadrant multiplier in which the voltage difference between the inverting and noninverting inputs of the amplifier is multiplied by a variable as set by the current flow at a control pin.
Preferably the variable gain amplifier is a differential gain amplifier. Advantageously the inverting and non-inverting inputs of the differential amplifier are connected to first and second outputs, respectively, of a transducer, such as a variable reluctance transducer. Such an arrangement provides for common mode rejection of signals appearing simultaneously at both inputs. A potential divider may be provided preceding each input of the variable gain block in order to protect it from higb input voltage, and to match the transducer output amplitude to amplifier input range.
As an alternative, or in addition to use of a variable gain amplifier, the variable gain block may utilise digitally switched resistor strings in attenuators, or as part of amplifier feed back loops, or may utilise field effect transistors to simulate voltage controlled resistors which again may be part of potential dividers or feed back loops. Thus the term variable gain block may encompass a variable attenuator.
Preferably the output of the variable gain block is monitored in order to derive a variable gain control signal. The peak value of the output may be stored in a storage device and used to control the gain of the variable gain block Advantageously, the peak value is allowed to decay with time in order to allow the signal gain of the variable gain block to vary in time in order to cope with changes in the input signal amplitude.
Preferably the output of the variable gain block is provided to a threshold crossing detector.
Advantageously the threshold crossing detector is a zero crossing detector. This allows a digital representation of the analogue input signal to be formed. When the signal processing circuit is used with a toothed or slotted wheel and a variable reluctance transducer, the output of the threshold detector indicates those times at which the tooth or slot, of the wheel is aligned with a pole of the variable reluctance sensor.
Advantageously the output of the threshold detector or the output of the variable gain block, may be capacitively coupled in order to detect the edges of the teeth or slots. The alternating current resulting from use of capacitive coupling may be operated on by a glitch reject element which serves to block unwanted noise pulses which are identified by virtue of the fact that they are narrower than a predetermined minimum width.
It is thus possible to provide a signal processing circuit for use with a variable reluctance transducer.
According to a second aspect of the present invention, there is provided a speed andlor position measurement device, comprising a magnetic element having position markers, a variable reluctance transducer and a signal processing circuit according to the first aspect of the present invention.
The present invention will further be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 schematically illustrates a toothed wheel of the type found in automobiles, and a variable reluctance transducer and associated signal processing circuit;
Figure 2 is a circuit diagram of a signal processing circuit constituting an embodiment of the present invention; and
Figure 3a to 3d shows various waveforms within the signal processing circuit of Figure 2.
As shown in Figure 1, a ferrous wheel 2, which is mounted on an engine crank shaft (not shown) is provided with a plurality of teeth 4. The teeth 4 are, in general equispaced.
However, one or more of the teeth may be made of a different size or may be omitted, in order to provide a position marker. Such a amarker enables an engine management system to identify a predetermined point of rotation of the crank shaft and thereby calculate the crank shaft position subsequent to that point by counting the passage of teeth past a variable reluctance transducer 6.
A variable reluctance transducer typically comprises a coil of wire wound around a magnetic pole piece. The pole piece forms a magnetic circuit with the wheel 2 and the flux flowing through the magnetic circuit varies as a function of the gap between the sensor 6 and the wheel 2, which varies as the teeth pass beneath the sensor. The voltage induced in the coil of the sensor 6 is a function of the rate of change of flux. Thus for an engine which may run as fast as 7000 rpm, and which may experience cranking speeds in the order of 200 rpm, the induced voltage may vary by approximately 35 times in amplitude.
First and second outputs 8 and 10 of the transducer are provided to a signal processing circuit 20. An embodiment of the signal processing circuit 20 is shown in Figure 2. An operational transconductance amplifier 30 has inverting and non-inverting inputs connected to the first and second outputs, respectvely, of the variable reluctance transducer via resistive potential dividers 32 and 34, respectively. An output ofthe transconductance amplifier 30 is connected to a voltage follower 36 and to a first end of resistor 120, a second end of which is connected to ground. An output of the voltage follower 36 is connected to an input of a gain control circuit, generally indicated as 40, and also to a non.inverting input of a zero crossing detector, indicated generally as 42.
The gain control circuit 40 comprises a diode 50 which half-wave rectifies the output of the voltage follower 36 and supplies chase to a storage capacitor 52 via a resistor 54. The capacitor can also discharge to a negative supply potential via resistors 54, 56 and 58 in series. An inverting input of an operational amplifier 60 configured as an integrator is connected to the node formed between resistors 56 and 58. The non-invening inpuT of the operational amplifier 60 is connected to ground. A capacitor 62 is connected between an output of an amplifier 60 and the inverting input thereof. The output of the amplifier 60 is provided via a diode 64 and resistor 66 to a gain control pin of the transconductance amplifier 30. The gain control pin is also connected to the positive supply rail, Vcc, via a resistor 68 which serves to set the minimum gain of the amplifier 30.
The zero crossing detector comprises an comparator 80 whose inverting input is connected to the output of the voltage follower 36. Resistor 100, diode 102 and resistor 104 are connected in series between the positive supply rail, Vcc, and ground. The non-inverting input of the comparator 80 is connected to the node formed between diode 102 and resistor 104 in order to receive an anning threshold therefrom, which marks the voltage at which an output of the comparator 80 switches low. The output of the comparator 80 is connected to the supply rail Vcc via a pull up resistor 106, and also to ground via capacitor 108 and resistor 110 in series. A Schmitt inverter 112 has an input connected to the node formal between capacitor 108 and resistor 110, via resistor 111. An output of the Schmitt inverter 112, fonns the output of the signal prOcessing circuit.
In use, the transconductance amplifier forms an output signal which is dependant on the difference between the voltages at its inverting and non. inverting inputs, multiplied by its transconductance. The transconductance is proportional to the bias cunent flowing into the control pin of the transconductance amplifier. The transconductance amplifier provides an output current which is converted into a voltage by virtue of flowing to ground through the resistor 120. This voltage is buffered by the voltage follower 36. The buffered output voltage is half wave rectified by diode 50 and stored on capacitor 52. The voltage on capacitor 52, as divided by the potential dividers formed by resistors 51, 56 and 58 is supplied to the inverting input of amplifier 60. Amplifier 60 is configured as an integrator and consequently the output voltage thereof will ramp in such a direction until such time as the feedback via capacitor 62 brings the voltage at the inverting and non-inverting inputs thereof into conformity with one another.
When the amplitude of the output of the transconductance amplifier 30 is large, capacitor 52 is charged up, and this eventually causes the voltage at the inverting input of amplifier 60 to exceed the ground potential. The integrator then acts to reduce the output voltage of the amplifier 60 which in turn reduces the amount of current supplied to the transconductance amplifier 30 via diode 64 and resistor 66. Thus the gain of the transconductance amplifier is reduced.
When the output of the transconchrctaace amplifier is relatively small in magnitude, the capacitor 52 is only charged to a small voltage, and consequently the voltage at the inverting input of the amplifier 60 is less than ground This causes the integrator formed around amplifier 60 to ramp upwards thereby causing more current to flow to the transconductance amplifier diode 64 and resistor 66. Thus the gain of the transconductance amplifier is increased.
Thus an automatic gain control is provided which varies the gain of the transconductance amplifier in order to stabilize the amplitude of the signals at the output of the transconductance amplifier.
The output of the voltage follower is compared with the arming threshold at the comparator SO. Once the voltage at the output of the transconductance amplifier (as buffered by the voltage follower) exceeds the arming threshold, the comparator switches low. This causes current from resistor 100 to be diverted via diode 122 to the output of the comparator 80.
Thus the non-invening input of the comparator becomes connected to the ground potential via resistor 104 and consequently now looks for the next zero crossing point, which will be signalled when the output of the comparator switches high.
The comparator output is capacitively couple to the input. of the Schmitt inverter by capacitor 10s. Furthennote, the comparator output must remain low for longer than a time period set by the time constant of capacitor 108 and resistor 110 before the next positive going edge on the comparator output is able to transfer a sufficiently large pulse through the capacitor 108 to the input of the Schurittinvener in order to cause a transition to appear at the output of the inverter 112. Thus glitches are filtered from the system.
Figures 3a to 3d show comparisons of the signals seen at positions A, B and C in the circuit of Figure 2, together with the signal at the output thereof, OXP.
As can be seen, a real signal causes tbe.signal at the input of the schmitt inverter to reach the switching threshold for low to high transitions, Vinhigh, but glitches do not.
It is thus possible to provide a signal processing circuit for use with a variable reluctance transducer which utilises an automatic gain control block in order to stabilise its performance in the presence an input signal having a large dynamic range. The circuit also avoids the necessity to use threshold level compcnsation techniques in order to set the detection threshold in order to determine wben the teeth and variable reluctance sensor are aligned with one another.
Claims (9)
- CLAIMS 1. A signal processing circuit, comprising a variable gain block, means for controlling the variable gain block so as to urge an amplitude of an output signal thereof to fall within a predetermined range, and a threshold crossing detector responsive to the output signal.
- 2. A signal processing circuit as claimed in claim 1, in which the variable gain block is a transconductance amplifier.
- 3. A signal processing circuit as claimed in claim 2, in which the amplifier is a differential amplifier having inverting an non-inverting inputs connected to first and second outputs, respectively, of a transducer so as to provide common mode rejection.
- 4. A signal processing apparatus as claimed in any one of the preceding claims, in which the variable gain block includes a variable attenuator.
- 5. A signal processing apparatus as claimed in any one of the preceding claims, in which the output of the variable gain block is monitored in order to derive a variable gain control signal.
- 6. A signal processing apparatus as claimed in claim 5, in which the peak value of the output is stored in a storage device and used to control the gain of the variable gain block.
- 7. A signal processing apparatus as claimed in claim 6, in which the peak value is allowed to decay with time.
- 8. A signal processing apparatus as claimed in any one of the preceding claims, in which the threshold crossing detector is a zero crossing detector.
- 9. A signal processing apparatus as claimed in any one of the preceding claims, in which a low pass filter is provided such that glitches are filtered out.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9803640A GB2334636A (en) | 1998-02-20 | 1998-02-20 | Dynamic range control for a threshold detector |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9803640A GB2334636A (en) | 1998-02-20 | 1998-02-20 | Dynamic range control for a threshold detector |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9803640D0 GB9803640D0 (en) | 1998-04-15 |
| GB2334636A true GB2334636A (en) | 1999-08-25 |
Family
ID=10827346
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9803640A Withdrawn GB2334636A (en) | 1998-02-20 | 1998-02-20 | Dynamic range control for a threshold detector |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2334636A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011152946A1 (en) * | 2010-06-03 | 2011-12-08 | Allegro Microsystems, Inc. | Motion sensor, method, and computer-readable storage medium providing a motion sensor that can rapidly calibrate gains |
| US8446146B2 (en) | 2010-06-03 | 2013-05-21 | Allegro Microsystems, Inc. | Motion sensor, method, and computer-readable storage medium providing a motion sensor with a validated output signal from the motion sensor |
| US8450996B2 (en) | 2010-06-03 | 2013-05-28 | Allegro Microsystems, Llc | Motion sensor, method, and computer-readable storage medium providing a motion sensor with a magnetic field sensing element for generating a magnetic field signal and a state processor to identify a plurality of states corresponding to ranges of values of the magnetic field signal having a reduced amount of state chatter |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4258324A (en) * | 1977-08-29 | 1981-03-24 | The Bendix Corporation | Signal conditioning circuit for magnetic sensing means |
| DE3115237A1 (en) * | 1981-04-15 | 1982-11-04 | Robert Bosch Gmbh, 7000 Stuttgart | Inductive transmitter arrangement |
| US4363979A (en) * | 1979-11-30 | 1982-12-14 | Robert Bosch Gmbh | Evaluation circuit for electrical signals |
| US4687952A (en) * | 1984-02-06 | 1987-08-18 | United Technologies Corporation | Dynamic angular position sensor for a reference gear tooth |
| EP0875732A2 (en) * | 1997-04-28 | 1998-11-04 | Allegro Microsystems Inc. | Method for centering a signal within the dynamic range of a peak detecting proximity detector |
-
1998
- 1998-02-20 GB GB9803640A patent/GB2334636A/en not_active Withdrawn
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4258324A (en) * | 1977-08-29 | 1981-03-24 | The Bendix Corporation | Signal conditioning circuit for magnetic sensing means |
| US4363979A (en) * | 1979-11-30 | 1982-12-14 | Robert Bosch Gmbh | Evaluation circuit for electrical signals |
| DE3115237A1 (en) * | 1981-04-15 | 1982-11-04 | Robert Bosch Gmbh, 7000 Stuttgart | Inductive transmitter arrangement |
| US4687952A (en) * | 1984-02-06 | 1987-08-18 | United Technologies Corporation | Dynamic angular position sensor for a reference gear tooth |
| EP0875732A2 (en) * | 1997-04-28 | 1998-11-04 | Allegro Microsystems Inc. | Method for centering a signal within the dynamic range of a peak detecting proximity detector |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011152946A1 (en) * | 2010-06-03 | 2011-12-08 | Allegro Microsystems, Inc. | Motion sensor, method, and computer-readable storage medium providing a motion sensor that can rapidly calibrate gains |
| US8446146B2 (en) | 2010-06-03 | 2013-05-21 | Allegro Microsystems, Inc. | Motion sensor, method, and computer-readable storage medium providing a motion sensor with a validated output signal from the motion sensor |
| US8450996B2 (en) | 2010-06-03 | 2013-05-28 | Allegro Microsystems, Llc | Motion sensor, method, and computer-readable storage medium providing a motion sensor with a magnetic field sensing element for generating a magnetic field signal and a state processor to identify a plurality of states corresponding to ranges of values of the magnetic field signal having a reduced amount of state chatter |
| US8680848B2 (en) | 2010-06-03 | 2014-03-25 | Allegro Microsystems, Llc | Motion sensor, method, and computer-readable storage medium providing a motion sensor that adjusts gains of two circuit channels to bring the gains close to each other |
| US8686720B2 (en) | 2010-06-03 | 2014-04-01 | Allegro Microsystems, Llc | Motion sensor, method, and computer-readable storage medium providing a motion sensor with a validated output signal from the motion sensor |
| US9170128B2 (en) | 2010-06-03 | 2015-10-27 | Allegro Microsystems, Llc | Motion sensor, method, and computer-readable storage medium providing a motion sensor with a vibration processor to set a state of a flag in response to selected ones of a plurality of test results being indicative of a passing conditions |
| US9175981B2 (en) | 2010-06-03 | 2015-11-03 | Allegro Microsystems, Llc | Motion sensor, method, and computer-readable storage medium providing a motion sensor generating a signal having signal states with a reduced amount of state chatter |
| KR101831708B1 (en) | 2010-06-03 | 2018-02-23 | 알레그로 마이크로시스템스, 엘엘씨 | Motion sensor, method, and computer-readable storage medium providing a motion sensor that can rapidly calibrate gains |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9803640D0 (en) | 1998-04-15 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US6291989B1 (en) | Differential magnetic position sensor with adaptive matching for detecting angular position of a toothed target wheel | |
| JP2746698B2 (en) | Circuit device for processing signals generated by a variable reluctance electromagnetic rotation sensor | |
| US5442283A (en) | Hall-voltage slope-activated sensor | |
| US4169232A (en) | Signal conditioning circuit for magnetic sensing means | |
| US4764685A (en) | Method and circuit configuration for processing the output signals of a rotational speed sensor | |
| US5736852A (en) | Circuit and method for conditioning a wheel speed sensor signal | |
| JP3336668B2 (en) | Sensor signal processing device | |
| US4258324A (en) | Signal conditioning circuit for magnetic sensing means | |
| JPH02216018A (en) | Method and apparatus for detecting passage of individual rotor wane of rotary machine in front of fixed sensor | |
| US4083423A (en) | Vehicle road speed signal source | |
| US4460867A (en) | Method and circuit for measuring of current | |
| US4609869A (en) | Magnetic sensor and circuit for detecting the edge of a target as it passes the centerline of the sensor | |
| US6636033B2 (en) | Sensor apparatus and method for generating an output signal of a sensor apparatus | |
| EP0046006B1 (en) | Electromagnetic transducer | |
| GB2334636A (en) | Dynamic range control for a threshold detector | |
| US4039931A (en) | System to sense a marker on a rotating body | |
| US6433533B1 (en) | Giant magneto-impedance(GMI) spin rate sensor | |
| EP0516687B1 (en) | Signal conditioning circuit | |
| JPH04272449A (en) | Method and device for evaluating signal | |
| US5606257A (en) | Device for forming a square-wave signal and detecting a reference mark from a sinusoidal signal with a singularity | |
| US6268721B1 (en) | Low cost binary encoded crankshaft position sensor | |
| US4866376A (en) | Cross-oil instrument having testing apparatus for vehicular sensor disconnection indication | |
| EP0166699A1 (en) | Circuit for detecting the passage through zero of the signal generated by an electromagnetic sensor of the phonic wheel type | |
| US5345171A (en) | Apparatus including a selectively connectable isolation transformer for determining the speed and direction of a rotating object | |
| EP0973258A2 (en) | Threshold crossing discrimination for oscillatory signals |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |