ATS610 Ver la hoja de datos (PDF) - Allegro MicroSystems
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ATS610 Datasheet PDF : 16 Pages
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ATS610LSA AND ATS611LSB
DYNAMIC, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT
GEAR-TOOTH SENSORS
DEVICE DESCRIPTION — Continued
Differential vs. Single-Element Sensing. The differen-
tial Hall-element configuration is superior in most applica-
tions to the classical single-element gear-tooth sensor.
The single-element configuration commonly used
(Hall-effect sensor mounted on the face of a simple
permanent magnet) requires the detection of a small
signal (often <100 G) that is superimposed on a large
back-biased field, often 1500 G to 3500 G. For most
gear/target configurations, the back-biased field values
change due to concentration effects, resulting in a varying
baseline with air gap, with valley widths, with eccentrici-
ties, and with vibration. The differential configuration
cancels the effects of the back-biased field and avoids
many of the issues presented by the single Hall element.
NOTE — 10 G = 1 mT, exactly.
Peak-Detecting vs. AC-Coupled Filters. High-pass
filtering (normal ac coupling) is a commonly used tech-
nique for eliminating circuit offsets. AC coupling has
errors at power up because the filter circuit needs to hold
the circuit zero value even though the circuit may power
up over a large signal. Such filter techniques can only
perform properly after the filter has been allowed to settle,
which is typically greater than one second. Also, high-
pass filter solutions cannot easily track rapidly changing
baselines such as those caused by eccentricities. Peak
detection switches on the change in slope of the signal
and is baseline independent at power up and during
running.
Track-and-Hold Peak Detecting vs. Zero-Crossing
Reference. The usual differential zero-crossing sensors
are susceptible to false switching due to off-center and
tilted installations, which result in a shift in baseline that
changes with air gap. The track-and-hold peak-detection
technique ignores baseline shifts versus air gaps and
provides increased immunity to false switching. In addi-
tion, using track-and-hold peak-detecting techniques,
increased air gap capabilities can be expected because a
peak detector utilizes the entire peak-to-peak signal range
as compared to zero-crossing detectors that switch on
fixed thresholds.
NOTE — “Baseline” refers to the zero-gauss differen-
tial where each Hall-effect element is subject to the
same magnetic field strength.
TARGET
T A = 25°C
-2000
-2500
-3000
-3500
-4000
AIR GAP = 2.5 mm
AIR GAP = 2.0 mm
AIR GAP = 1.5 mm
AIR GAP = 1.0 mm
AIR GAP = 0.5 mm
-4500
-5000
0
10
20
30
40
50
60
ANGLE OF TARGET ROTATION IN DEGREES
Dwg. GH-061-1
Single-element flux maps
showing the impact of varying valley widths
TARGET
T A = 25°C
1500
1000
500
AIR GAP = 0.5 mm
AIR GAP = 1.0 mm
0
-500
-1000
AIR GAP = 2.5 mm
AIR GAP = 2.0 mm
AIR GAP = 1.5 mm
-1500
0
10
20
30
40
50
ANGLE OF TARGET ROTATION IN DEGREES
Differential flux maps vs. air gaps
60
Dwg. GH-061
115 Northeast Cutoff, Box 15036
10
Worcester, Massachusetts 01615-0036 (508) 853-5000
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