UZZ9000 APPN, PDF - CIEKAWE, PDF ELEKTRONIKA

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APPLICATION NOTE
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Philips
Semiconductors
Philips
Semiconductors
Contactless Angle Measurement Using
KMZ41 and UZZ9000
Application
Note AN00023
Abstract
Angle measurement is frequently required in both automotive and industrial applications. Contactless methods
have the advantage that they are free of wear. If a magnetic field acts as the transmitter between the physical
value to be measured and the actual sensor, the magnetic system and the signal conditioning electronics can be
encapsulated separately making such systems robust against dirt, dust and liquid as well as mechanical
destruction. Among this class of measurement systems, those using the magnetoresistive effect (MR effect) are
characterised by the additional feature that they evaluate the direction of the magnetic field and not the field
strength. Therefore MR based systems tolerate variations in field strength caused by ageing or temperature-
sensitivity of the magnet as well as mechanical tolerances. This recommends MR based systems for applications
where robust, precise, and also cost-efficient solutions are required.
Philips Semiconductors provides a two-chip solution for an application-specific MR angle measurement system. It
consists of the magnetoresistive sensor KMZ41 and the sensor signal conditioning IC UZZ9000. The UZZ9000
was designed for the usage with the KMZ41 and therefore provides an optimised interface to this sensor. It can
also be used in conjunction with other sensors providing two sinusoidal output signals with a 90°-phase shift.
© Philips Electronics N.V. 2000
All rights are reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copy-
right owner.
The information presented in this document does not form part of any quotation or contract, is believed to be
accurate and reliable and may be changed without notice. No liability will be accepted by the publisher for any
consequence of its use. Publication thereof does not convey nor imply any license under patent- or other industrial
or intellectual property rights.
2
 Philips
Semiconductors
Contactless Angle Measurement Using
KMZ41 and UZZ9000
Application
Note AN00023
APPLICATION NOTE
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Keywords
UZZ9000
KMZ41
Contactless Angle Measurement
Magnetoresistive Sensors
Date: 24 March 2000
3
 Philips
Semiconductors
Contactless Angle Measurement Using
KMZ41 and UZZ9000
Application
Note AN00023
Summary
This report describes how to build a MR based measurement system using the magnetoresistive sensor KMZ41
and the sensor signal conditioning IC UZZ9000 available from Philips Semiconductors.
The first section gives an introduction into MR technology. It is shown that the magnetoresistive effect is naturally
an angular effect recommending its use for angle measurement applications. The next sections describe the
basic function of a system consisting of the sensor KMZ41 and the sensor signal conditioning IC UZZ9000. The
KMZ41 sensor comprises two Wheatstone bridges on one substrate. This gives a very good matching of
mechanical and electrical properties. The signal conditioning IC UZZ9000 is optimised for the usage with the
KMZ41 but can also be used in conjunction with any other sensor providing two sinusoidal signals with 90°-
phase shift, such as resolver applications, Hall sensors and GMR sensor. This mixed signal IC provides an
analog, ratiometric output signal that allows a direct replacement of present potentiometer solutions. The input
angular range can be adjusted between 0° to 30° and 0° to 180° in steps of 10°. Also, the zero point of the
mechanical angle is user programmable between +/- 5° in steps of 0.5°. Both KMZ41 and UZZ9000 are
specified between -40°C to +150°C for normal operation.
The last section describes the non-ideal cases and their impact on system accuracy. The error analysis based on
a 3-Sigma confidence interval shows that the absolute accuracy is better than 0.6° in a temperature range from -
40°C to +85°C. This corresponds to an relative error better than 0.4% referred to 180° full scale. At 150°C, the
maximum absolute error is better than 1.2°. The resolution of the measurement system is better than 0.1° at all
temperatures. If a field strength of 100 kA/m (1250 Gauss) is used for the magnetic system, then the hysteresis
lies within the resolution and is therefore not measurable.
4
 Philips
Semiconductors
Contactless Angle Measurement Using
KMZ41 and UZZ9000
Application
Note AN00023
Contents
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4.1
L
AYOUT OF THE
KMZ41 S
ENSOR
................................................................................................................. 14
4.2
I
NPUT AND
O
UTPUT
S
IGNALS
....................................................................................................................... 14
4.3
M
AGNETS AND
M
AGNET
A
RRANGEMENTS
..................................................................................................... 16
4.4
O
THER
M
ECHANICAL
S
ET
-
UPS
..................................................................................................................... 17
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5.1 G
ENERAL
D
ESCRIPTION
............................................................................................................................... 19
5.2 C
HARACTERISTICS OF
I
NPUT AND
O
UTPUT
S
IGNALS
..................................................................................... 22
5.3 A
DJUSTING THE
A
NGULAR
R
ANGE AND THE
Z
ERO
P
OINT
O
FFSET
.................................................................. 24
5.3.1 Changes of the Output Curve Characteristic .................................................................................... 24
5.3.2 How to Set a Certain Angular Range ................................................................................................ 25
5.3.3 How to Set a Zero Point Offset ......................................................................................................... 26
5.4 O
FFSET
T
RIMMING
...................................................................................................................................... 27
5.4.1
Trim Interface .................................................................................................................................... 28
5.4.2
How to Enter the Trim Mode ............................................................................................................. 29
5.4.3
Offset Calibration .............................................................................................................................. 29
5.5
R
ESET
........................................................................................................................................................ 32
5.6
D
IAGNOSTIC
................................................................................................................................................ 33
5.7
M
EASUREMENTS
D
YNAMICS
........................................................................................................................ 33
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6.1
S
INGLE
M
EASUREMENT
S
YSTEM
.................................................................................................................. 35
6.2
F
AULT
T
OLERANT
S
YSTEMS
......................................................................................................................... 36
6.3
T
YPICAL
A
PPLICATION
C
IRCUIT
.................................................................................................................... 38
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7.1 S
ENSOR
KMZ41 ......................................................................................................................................... 39
7.1.1 Less Magnetic Field Strength............................................................................................................ 39
7.1.2 Effects of Inhomogeneous Magnetic Fields ...................................................................................... 42
7.1.3 Non-Ideal Properties of the Components.......................................................................................... 43
Offset and Offset Drift ................................................................................................................................................43
Different Signal Amplitudes........................................................................................................................................45
Phase Difference between Channels.........................................................................................................................46
7.1.4 D
ISCUSSION OF
D
IFFERENT
E
FFECTS
....................................................................................................... 47
7.2 S
IGNAL
C
ONDITIONING
IC UZZ9000 ............................................................................................................ 47
Example: ....................................................................................................................................................................48
7.3 A
PPLICATION
E
XAMPLE FOR
E
RROR
C
ALCULATION
....................................................................................... 48
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5
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