General Rotational speed measurement 1998 File under Discrete Sem
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General Rotational speed measurement
1998 File under Discrete Semiconductors, SC17
Philips Semiconductors
Rotational speed measurement
ROTATIONAL SPEED MEASUREMENT Contents Principles standard set-ups Philips' sensors rotational speed measurement Application information Information advanced users applications Hybrids Frequency doubling Eddy currents Dual sensor set-ups characteristics Sensor properties without signal conditioning electronics. Principles standard set-ups basic properties magnetoresistive technique make highly suitable measuring rotational angular speed object: offers high sensitivity (about times stronger than Hall effect), which allows large gaps (>2.5 used between target sensor, produces strong primary signals, making sensing set-up largely insensitive disturbances.
General
very wide operating frequency range MHz), with sensor still producing signal down allowing very speed applications (e.g. navigation systems). sensors metal-based, they operate making them extremely well suited high temperature situations. These commonly found automotive applications such braking systems under bonnet, near engine (cam crankshaft speed measurement, example). Magnetoresistive sensors highly insensitive mechanical stress comparison Hall effect sensors, relatively small piezoresistive effect permalloy material, they encapsulated simply cost-effectively. Since magnetoresistive effect cannot measure rotational speed directly, practical set-up uses magnetic field applied sensor from permanent magnet. Typically, this `back-biasing' magnet simply glued back sensor, that sensor sees uniform parallel field with component sensitive direction sensor output zero. Then, ferromagnetic target with teeth brought close sensor, field back-biasing magnet affected target influence depends position target front sensor (see Fig.1).
gear handbook, full pagewidth wheel rack magnet magnetic field lines
direction motion
sensor
MBE073
Fig.1 Speed detection using magnetoresistive sensor.
1998
Philips Semiconductors
Rotational speed measurement
`symmetric' position, where tooth valley exactly front sensor, target effect field seen sensor, sensor still gives zero output. `non-symmetric' position, target rotates front target, effect thus amplitude sensor output varies according actual wheel position. peak value output, Vpeak, depends magnetic field strength biasing magnet, distance between sensor target and, obviously, structure target. Large, solid targets will give stronger signals larger distances from sensor than small targets. general, `size' structure this application described relationship between wheel diameter number teeth, described Table
General
handbook, halfpage
mV/div.)
MGG459
Fig.2 Typical oscilloscope trace rotational speed measurement.
Table
Gear wheel dimensions (see Fig.3) SYMBOL DESCRIPTION UNIT
German ASA(1) Note conversion from DIN: 25.4 mm/DP; 25.4 pitch diameter inches) diametric pitch z/PD circular pitch inch inch-1 inch number teeth diameter module pitch
pitch
handbook, halfpage
pitch diameter
MRA964
Fig.3 Gear wheel dimensions.
1998
Philips Semiconductors
Rotational speed measurement
Figure shows typical relationship between primary output signal (i.e. with signal conditioning electronics) KMZ10B sensor (with back biasing magnet) various target structures, with module `m'. This principle so-called `passive' ferrous targets, where target itself magnetized (see Fig.5). sensors naturally bi-stable devices, with stable opposite operating characteristics, they also need external magnetic field stabilization. With suitably magnetized magnet positioned correctly, single magnet perform both stabilization back-biasing. (For more details sensor stabilization, please refer General Introduction this handbook Appendix 'Active' targets also used, where target alternating magnetic poles. this case, target itself provides `working' field, back-biasing magnet required, only stabilization magnet, which smaller than ones used both stabilization back-biasing with passive targets. Also, should noted that active target need have teeth. `active' set-up shown Fig.6.
General
handbook, halfpage (peak)
MGD861
10-1
distance/mm
0.5; 0.75; 1.25; 2.5;
Fig.4
Typical relationship between airgap KMZ10B sensor, with back biasing magnet 4.35 used KMI15/1), target module, `m'.
1998
Philips Semiconductors
Rotational speed measurement
General
handbook, full pagewidth
gear wheel magnet magnetic field lines
current sensor amplifier, comparator
position
MGG460
Fig.5 Simple set-up using passive target.
handbook, full pagewidth
magnetic field lines magnetized target
current sensor amplifier, comparator
position
MGG461
Fig.6 Simple set-up using active target.
1998
Philips Semiconductors
Rotational speed measurement
structure active target expressed similarly that passive targets (Table this case, tooth/valley pair represented North-South magnetic pole pair. Figure shows typical relationship between primary output signal (i.e. with signal conditioning electronics) KM110B/2 sensor various active target structures, with module `m'.
General
Both measurement techniques inherently accurate, frequency output directly proportional rotational speed. Although principle, basic application requiring minimal accuracy, output from sensor used directly, practice signal conditioning circuitry stabilizes output from sensor ensures accurate speed measurement under varying environmental conditions. Typical conditioning includes filtering, amplification, temperature compensation switching hysteresis.
handbook, halfpage output voltage (VPP)
MGD860
airgap (m.m.)
Fig.7
Typical relationship between airgap KM110B/2 sensor active target module, `m'.
1998
Philips Semiconductors
Rotational speed measurement
Philips' sensors rotational speed measurement Practical rotational speed sensors always delivered complete with back biasing magnet, with signal conditioning circuitry contained separate both active passive set-ups. simplify system design, Philips developed series ready sensors, KMI15/X family, which comprises magnetoresistive sensor adapted version KMZ10B), ferrite back-biasing magnet advanced bipolar signal conditioning mounted single lead frame. three sensors family KMI15/1 KMI15/4 passive targets, KMI15/2 active targets. passive set-ups, magnets specially designed apply symmetrical magnetic field plane sensor field relative z-axis plane. symmetrical field plane (Figs provides back-biasing component x-direction sensor plane stabilizes magnetoresistive element, described earlier. active set-ups, KMI15/2 comes with small stabilization magnet (see Fig.11) needs back-biasing (the operational field being supplied target itself). These sensors provide compact design cost-effective customization possibilities and, they simple design-in, time-to-market significantly reduced. addition advantages described earlier, these sensors almost immune vibration effects inherent property magnetoresistive effect), used with large variety gear-tooth structures, resistant offer digital current output signal. two-wire digital current signal advantages considerably reduced wiring connections, which actually more significant cost than that sensor itself. sensor separated physically within encapsulation, optimize KMI15's high temperature performance that sensor then exposed higher temperatures than power dissipation will cause inhomogeneous heating sensor element).
handbook, halfpage
General
signal conditioning circuit, sensor output signal passed through filter, amplified then digitized comparator which built-in switching hysteresis, performed Schmitt trigger (for more details, refer section switching hysteresis). voltage control block provides stabilized power supply sensor, amplifier comparator itself stabilized bandgap reference diode. sensors were developed magnetoresistive devices with current output, which advantage using cost two-wire technology. They current sources, integrated into signal conditioning supplies base current output (partly used supply) second, switchable current source added when triggered amplified digitized sensor output signal. Thus, during operation output current, ICC, switches between (see Fig.8). set-up providing three-wire voltage output described later integrated sensor with three-wire open collector output under development.
MRA960
Fig.8 Current output signal.
1998
Philips Semiconductors
Rotational speed measurement
General
handbook, halfpage
magnet with direction magnetization
sensor
MBH778
Fig.9 Typical outline KMI15/1 rotational sensor module passive targets.
1998
Philips Semiconductors
Rotational speed measurement
General
handbook, halfpage
magnet with direction magnetization
sensor
MBH779
Fig.10 Typical outline KMI15/4 rotational sensor module passive targets.
1998
Philips Semiconductors
Rotational speed measurement
General
handbook, halfpage
magnet with direction magnetization
sensor
MBH777
Fig.11 Typical outline KMI15/2 rotational sensor module active targets.
1998
Philips Semiconductors
Rotational speed measurement
General
handbook, full pagewidth
VOLTAGE CONTROL
CONSTANT CURRENT SOURCE
SENSOR
AMPLIFIER
SCHMITT TRIGGER
SWITCHABLE CURRENT SOURCE
MRA958
Fig.12 Block diagram sensor signal conditioning circuitry.
handbook, full pagewidth
switchable constant current source Iref Iref
constant current source reference voltage
power supply
sensor
FILTER Preamplifier Schmitt trigger voltage stabilizer
Vref
MGG495
Fig.13 Sensor signal conditioning circuit diagram.
1998
Philips Semiconductors
Rotational speed measurement
SENSING DISTANCE MOUNTING Sensing distance defined distance between front sensor tips teeth, measured central axis magnet (see Fig.14). Above certain value `d', ceases vary between becomes constant KMI15 sensors optimized deliver stable digital output signal large range values have large switching hysteresis, avoid unwanted signals arising through vibrations. Variations temperature compensated signal conditioning residual temperature effect shown Fig.15. Movements ferromagnetic target wheel magnetic field sensor system will induce eddy currents wheel, generating offset voltage sensor's output which increases linearly with rotational speed. This reduces maximum sensing distance slightly higher frequencies, since this offset addition static offset, available voltage from switching hysteresis (set reduced, decreasing maximum airgap which sensor operates (switching hysteresis described more detail later this chapter). (Eddy currents also used positive effect some applications: Section "Information advanced users applications" later this chapter.) Finally, structure wheel itself will affect maximum sensing distance, according large well-defined teeth are. Figure shows variation maximum distance with tooth module KMI15/1.
handbook, halfpage
General
MBE074
(mm)
(kHz)
d(T); d(f);
Tamb
Fig.15 Maximum sensing distance KMI15/1 function temperature tooth frequency.
handbook, halfpage
MRA966
handbook, halfpage
sensor
gear wheel
module (mm)
MRA963
Fig.14 Sensor positioning.
Fig.16 Normalized maximum sensing distance function wheel module.
1998
Philips Semiconductors
Rotational speed measurement
When mounting KMI15, there important factors take into consideration: angle between symmetry axes sensor wheel plane) horizontal shift relative optimum sensor position. Both these values should minimized. Recommended tolerances optimal operating conditions Their effect shown Figs shift position x-direction very critical KMI15's performance, magnet's field component x-direction means that x-shift produces non-symmetrical behaviour (see Fig.19). optimum position when should case minimized, especially small values `d'. tilt plane negligible influence optimum sensing distance angles <4°.
handbook, halfpage
General
MRA998
(mm)
(mm)
Fig.17 Influence position tolerance maximum sensing distance KMI15/1.
handbook, halfpage
MRA999
handbook, halfpage
MRA982
(mm)
(mm)
(deg)
(mm)
Fig.18 Influence angular tolerance maximum sensing distance KMI15/1.
Fig.19 Influence position tolerance maximum sensing distance KMI15/1.
1998
Philips Semiconductors
Rotational speed measurement
SWITCHING HYSTERESIS Switching hysteresis included signal conditioning circuitry, prevent unwanted electrical switching KMI15 Mechanical vibration sensor gear wheel Electrical interference (EMC) Circuit oscillation very rotational speeds. Larger hysteresis provides better immunity disturbances also reduces sensing distance `d', compromise required between hysteresis sensing distance. KMI15 sensors have hysteresis maximum attainable distance will achieved with sensor signal level peak-to-peak. Figure shows typical KMZ10B sensor output signal values, with back-biasing magnet), with different target wheel modules shows clearly that hysteresis directly determines usable airgap. KMI15/1, maximum distance always >2.5 typically KMI15/4, maximum distance >2.0 typically mm). hysteresis test set-up shown Fig.20, together with test results function distance. This set-up allows simple testing products there direct correlation between test results obtained equivalent properties most commonly-used gear wheels. case gear wheel with sensor with expressed terms linear movement gear tooth hysteresis corresponds gear wheel diameter this hysteresis equivalent 0.32° rotation. Obviously, these figures will different different gear wheels.
General
MBE075
handbook, halfpage
(mm)
test assembly cc(high) cc(low)
iron
(mm)
Fig.20 Mechanically measured hysteresis KMI15 function sensing distance test assembly shown.
1998
Philips Semiconductors
Rotational speed measurement
CHARACTERISTICS KMI15/X determine sensor characteristics actual application, KMI15/4 used measure rotation toothed wheel 0.8).
General
peak voltage output signal, again with signal conditioning, shown Fig.22.
Sensor output
these measurements, output signal sensor (KMZ10B with back biasing magnet) measured with sensor placed distance from wheel, with signal conditioning. Figure shows oscilloscope trace obtained from full revolution wheel points where signal shows peak correspond missing teeth, effective change wheel module these points. Such well defined trace teeth `holes' demonstrates intrinsic high sensitivity sensor shows that well being able measure speed wheel, also used indicate reference marks such missing teeth (e.g. crankshaft applications) irregular target structures (e.g. camshaft applications).
handbook, halfpage
MGG470
Maximum
able define maximum given sensor, first necessary know behaviour sensor signal changes with measuring distance. Fig.21 Sensor signal over revolution.
handbook, full pagewidth Vpeak (mV)
MGG471
0.25 0.50 0.75 0.90 1.13 1.25 1.50 1.75 distance (mm)
Fig.22 Output signal from KMZ10B sensor with back-biasing magnet versus distance.
1998
Philips Semiconductors
Rotational speed measurement
hysteresis voltage peak-to-peak peak), results show theoretical maximum 1.13 However, this does take into account eddy currents that induced wheel rotates, which produce offset voltage proportional speed (for more details, section eddy currents later this chapter). Taking eddy currents into account, well other factors producing offsets such non-optimal sensor positioning, maximum permissible reduced
General
Eddy currents
influence eddy currents measured increasing wheel rotation speed from through 3000 with sensor placed from wheel. From graph below, maximum additional speed-dependent offset voltage determined approximately ±2.8 with sign determined direction measurement. application requires large gap, special attention should given target material structure reduce unwanted influences from eddy currents.
handbook, full pagewidth
offset voltage (mV)
MGG472
Voff
1000 1500 2000 2500 signal frequency (Hz) 3000
Fig.23 Offset voltage KMI15/4 versus frequency, both directions.
1998
Philips Semiconductors
Rotational speed measurement
Repeatability
this test, speed wheel measured using sensors: KMI15/4 front teeth reference sensor front small reference (rare earth) magnet placed wheel. essential that measurements taken same tooth, this second sensor used trigger counter same moment every revolution. problem measuring repeatability sensor that over length time taken make measurements, actual velocity wheel vary. This basic error within measurement technique, test fact measures relative repeatability achievable with sensor. Test conditions: Target 1000 Sensing distance measurements were taken every seconds; results tabulated below. From this data average calculated. shown table, during measurements motor changed speed approximately 0.35%. result last column gives comparison between KMI15/4 values reference sensor values. maximum difference between sensors only 0.161. This result also shown Fig.25. Table Repeatability results 15/4 MEAS. (µs) 840.7 839.6 842.1 841.4 840.4 836.9 835.9 835.3 836.9 839.0 838.83 REFERENCE SENSOR t/tm +2.349 +0.918 +3.898 +3.064 +1.872 -2.301 -3.493 -4.208 -2.301 +0.203
Vref magnet KM110B/2
General
handbook, halfpage
sensor
magnet
KMI10/4 MOTOR
PM6654 COUNTER gate
MGG473
Fig.24 Repeatability measuring arrangement.
t/tm (KMZ) t/tm (KM) (ms) 60.4563 60.3605 60.4036 60.4931 60.4261 60.1753 60.1042 60.0554 60.1851 60.3283 60.31419
Note: convert tolerance degrees, formula used: 0.01% 83.883 83.883 ns/60.31419 0.0005.
1998
Philips Semiconductors
Rotational speed measurement
General
handbook, full pagewidth
(counter) -0.2 -0.1 t/tmKMZ t/tmKMI
MGG474
Fig.25 Repeatability measurements (X).
shown calculation, tolerance equates 0.005 degrees. maximum tolerance therefore repeatability sensor better than 0.0008 degrees. effect three independent parameters test (two sensors counter), exact repeatability figures single sensor cannot derived, what these results clearly show that repeatability KMI15/4 much better than worst result this particular test. FUNCTIONAL TESTING KMI15/1 ROTATIONAL SPEED
SENSOR
handbook, halfpage
Helmholtz coils sensor
This carried steps, testing switching behaviour sensitivity electromagnetic stimulation device Helmholtz coil. set-up used tests, with direction stimulating field parallel sensitive direction sensor, shown Fig.26.
magnet
magnetic field lines magnet
MGG486
Fig.26 Electromagnetic stimulation KMI15/1 sensor.
1998
Philips Semiconductors
Rotational speed measurement
Control sensitivity
measurement sensitivity (calculating minimum sensing distance) KMI15/1 more complex operation. Based same coil arrangement shown Fig.26, coil sensor linked together part electronic control loop, shown Fig.28. Sensitivity tested measuring minimum magnetic fields both positive negative rotational directions) required switch sensor from current state high back again. This done automatically ramping magnetic field control loop. peak-to-peak difference minimum magnetic field strength (Hmin) generates output voltage when dropped across magnetoresistive element. This voltage corresponds hysteresis voltage Vhyst Schmitt-trigger circuit signal conditioning hysteresis voltage direct indicator sensitivity, this test provides very quick accurate method determining maximum sensing distance (larger distances Hmin, smaller distances Hmin). Using number gear wheels test targets, found with samples tested that maximum sensing distance rotational directions dmax (KMI15/1).
General
With current switching hysteresis final result showed high current levels Ilow ±1.4 Ihigh 14.0 ±2.8 showing that switching behaviour within acceptable parameters most applications.
handbook, halfpage
MGG488
Hmin2
Hmin1
Ihigh
Ilow
Switching behaviour
magnetic field switched between Hlow -0.84 kA/m Hhigh +0.84 kA/m, causing KMI15/1 output status switch high measuring output current, possible check switching behaviour.
Fig.27 Magnetic field current output versus time.
handbook, full pagewidth
SENSOR
COMPARATOR
INTEGRATOR
COIL
MGG487
Fig.28 Simplified control loop sensitivity measurement.
1998
Philips Semiconductors
Rotational speed measurement
Information advanced users applications DIRECTION DETECTION rotational set-ups used measure rotational direction well speed, improve measurement sensitivity set-up, using sensors comparing phase difference (although exact set-up will depend structure target). Three examples described below: Circuit using half-bridges KMZ10B sensor Dual KMI15/1 with toothed wheel Dual KMI15/1 with slotted wheel. "ONE SENSOR SOLUTION" This concept uses magnetoresistive sensor half-bridges single encapsulation. There will very small phase difference between outputs half-bridges when target wheel turns front sensor using separate signal processing each half, possible indicate direction with only sensor. bridge geometry fixed within sensor chip, there optimum wheel module within this constraint, wide range wheel pitches possible. target wheel does have optimum pitch, phase difference maximum sensor electronics will have relatively harder produce clear, well-defined signal. this case, additional filtering required. coupling useful, which means sensor cannot measure down with dual sensor set-ups described below). Without filtering, circuit could indicate zero speed would capable incremental counting, operating range would limited. DUAL KMI15/1 SENSORS WITH TOOTHED WHEEL mentioned, dual sensor set-ups used measure rotational direction well speed. Using KMI15/1 sensors separated least positioned angle (not equal angle between teeth), possible measure rotational speed direction toothed wheel down which cannot achieved using half-bridges. Ideally phase difference between outputs should resulting timing output signals indicates direction. This means that angle between sensors should proportional angle between adjacent teeth according relationship: 1/4).
ICC2
handbook, halfpage
General
distance between sensors less than interaction between magnets will cause offset voltage sensor bridges, which effect reducing maximum tooth-to-sensor measuring distance.
handbook, halfpage
toothed wheel
KMI10/1
1/4)
KMI10/1
MGG462
Fig.29 Measurement with toothed wheel.
ICC1
MGG463
Fig.30 Optimum output signal clockwise rotation.
1998
Philips Semiconductors
Rotational speed measurement
General
DUAL KMI15/1 SENSORS WITH SLOTTED WHEEL Instead toothed wheel, slotted wheel used. this case sensors mounted front wheel radially above surface.
handbook, halfpage
ICC1
MGG464
ICC2
slotted wheel set-up further adapted allow sensor-to-sensor distances less than sensors mounted next each other with opposite orientations, which reduces effect magnetic interaction. With this set-up, tolerances will limit maximum measuring distance, does have advantage that both sensors could housed same encapsulation, with single conditioning electronics direction detection, resulting simple application design.
Fig.31 Optimum output signals anti-clockwise rotation.
handbook, full pagewidth
slotted wheel
KMI15/1
KMI15/1
MGG465
1/4)
Fig.32 Measurement with slotted wheel.
1998
Philips Semiconductors
Rotational speed measurement
General
handbook, halfpage
slotted wheel
handbook, halfpage
position sensor
KMI15/1
KMI15/1
MGG466
magnetic ring
Fig.33 Alternative arrangement with short (<20 sensor-to-sensor distance.
MGG467
FREQUENCY DOUBLING active targets, magnetic sensors normally output electrical signal equivalent magnetic structure multipole rings, with period sensor signal equating single magnetic pole pair Driving KMZ10B without auxiliary magnet with magnetic fields above about kA/m, effectively doubles frequency magnetic pole pairs deliver signals same period. This because outside `symmetrical' position Fig.34), magnetic field sensor plane describes full rotation each pole pair passing front sensor sensor saturated, high magnetic field, basic cos2 relationship holds true between sensor output angle applied field (see Fig.35). more details this, please refer Appendix equations magnetoresistive effect Appendix sensor flipping. This improves resolution measurements resolution fixed, allows magnets with reduced pole numbers.
Fig.34 Frequency doubling arrangement using KMZ10 sensor.
1998
Philips Semiconductors
Rotational speed measurement
General
handbook, full pagewidth
signal
KMZ10
/degrees
weak field
strong field
MBH716
Fig.35 Sensor output with without bias magnet.
EDDY CURRENTS target rotates field magnet, eddy currents induced target, according target material rotational speed. These eddy currents themselves generate magnetic field addition field from magnet, resulting additional offset sensor output. standard applications, there therefore need increased hysteresis signal conditioning electronics (see Section "Switching hysteresis" earlier this chapter). This adverse effect sensor performance terms maximum sensing distance, leading reduced airgap, unless equipped with filter. However, these eddy currents themselves used measure speed metallic, non-ferrous wheel (e.g. copper). sensor measures magnetic field produced eddy currents induced wheel auxiliary magnet increases rotational speed matched increases level eddy currents. This type arrangement suitable permanent mounting simple tachometer.
handbook, halfpage
copper wheel
MGG468
Fig.36 Set-up measurement using eddy currents. 1998
Philips Semiconductors
Rotational speed measurement
General
handbook, full pagewidth
MGG469
(mV)
-3000 -2000
-1000 1000
(m/s)
2000 3000
Fig.37 Sensor output versus RPM.
CHARACTERISTICS sensitive electronic system connected other equipment unshielded cables, more susceptible electromagnetic effects. determine effects rotational sensors system using unshielded wire length, tests were carried out: firstly determine influence field waveguide; secondly, pulse along cable.
following parameters were used this test: Unmodulated frequency range maximum electrical field intensity Emax V/m. Amplitude modulated (AM) percentage modulation modulation frequency frequency range maximum electrical field intensity Emax V/m. set-ups used (see Figs with frequencies over MHz, mismatch could longer considered negligible. Also, reflected waves between waveguide amplifier were measured using disconnected directional coupler were included determination actual field intensity waveguide.
Influence electrical field waveguide
unshielded cable subjected electrical field waveguide (wave resistance sensor (EUT1) located outside waveguide connected cable second electronic device (EUT2) which turn, connected oscilloscope enable functional check sensor. waveguide powered sweep generator connected amplifier this test signal checked monitored waveguide input second oscilloscope. quality signal from first oscilloscope indicates interference from electrical field.
1998
Philips Semiconductors
Rotational speed measurement
General
handbook, full pagewidth
SWEEP GENERATOR
antenna
AMPLIFIER max.
cable
OSCILLOGRAPH VOLTAGE MEASUREMENT
OSCILLOGRAPH FUNCTION CHECK
MGG475
Fig.38 Test set-up with waveguide (antenna) MHz.
handbook, full pagewidth
SPECTRUM ANALYSER WITH LOCKED-IN OSCILLATOR
antenna
AMPLIFIER max.
DIRECTIONAL COUPLER
cable
OSCILLOGRAPH VOLTAGE MEASUREMENT
OSCILLOGRAPH FUNCTION CHECK
MGG476
Fig.39 Test set-up with waveguide (antenna) GHz.
1998
Philips Semiconductors
Rotational speed measurement
undesirable effects were observed sensor signal therefore system required resistance electromagnetic interference. Also, destructive test carried sensor with field intensities Emax throughout frequency range, destructive irreversible changes sensor parameters occurred.
General
currents i3(t) i4(t) clearly show oscillation where following peak values were obtained. i3max i4max basis i4max then voltage (see Fig.41) This voltage input low-pass filter which cut-off frequency kHz. According Fig.40, period away approximately i.e. frequency 62.5 MHz. This means that distance between more than four decades therefore, dB/decade (ideal low-pass), distance approximately between where represents input voltage trigger unit This clearly gives value which well below required limit.
Influence pulse along cable
Using following test circuit sensor, with connection points test pulse current measurement points indicated, currents were measured using passive current sensors storage oscilloscope. Here value i2(t) represents time variation test pulse connection point. response behaviour input test pulse (i2) measured under least favourable conditions with impedance grounding earth connection sensor output, resulting higher values i4max than normally experienced. Figure shows test pulse i2(t) with rise time approximately peak value i2max 4000
handbook, full pagewidth
test pulse SENSOR TRIGGER (±10%)
CONTROLLER
MGG481
Fig.40 Pulse test circuit diagram hybrid sensor.
1998
Philips Semiconductors
Rotational speed measurement
General
MGG482
handbook, halfpage
Test pulse
MGG483
handbook, halfpage
Test pulse
MGG484
handbook, halfpage
Test pulse
Fig.41 Oscilloscope traces showing.
1998
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