TMR Angle Sensor Guide

The TMR sensors of TDK are a new type of magnetic sensors utilizing a TMR element, which is a highly-sensitive reproducing element of an HDD head. The reading elements of HDD heads are based on the magnetoresistance effect, which refers to a change in resistance induced by the application of an external magnetic field. Since the 1980's, they have promoted significant improvement of the recording density of HDDs, while evolving into AMR (anisotropic magnetoresistance effect) elements, GMR (giant magnetoresistance effect)

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There are two main methods of arranging magnets and TMR angle sensors: On-axis (axial-end and shaft-end) and off-axis (extra-axial detection and outer ring detection), and good angular accuracy can be achieved with both arrangements.

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The output delay time of the sensor must be considered when detecting angles during rotary motion, such as in motor position control.

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No matter which sensor is used, compensation work for deterioration of angle accuracy due to assembly errors required engineers to make great efforts. An automatic compensation function was incorporated into the TAD2141 as a means of significantly reducing the effort required.

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Degradation of accuracy due to stray-field noise is a common problem for magnetic field sensors. Securing a distance between the source of stray field and the sensor, or placing a magnetic shield, are major restrictions on design and lead to higher system costs. In addition, it was difficult to select an appropriate design while adjusting the balance between compensation effectiveness and cost. As a solution, TDK proposes a method of suppressing magnetic stray-fields using multiple sensors. In the "summary of compensation measures" below, the effect of stray field is compensated by using the output difference of two sensors that output opposite phases to the magnetic field signal. By selecting the number of sensors to be used, rational countermeasures can be selected while considering the expected stray field and allowable angular error.

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TDK was the first in the world to commercialize automotive TMR sensors and began shipments in 2014.
TDK’s TMR sensors are used in a wide range of applications including automobiles, which are becoming increasingly automated and electrified, industrial equipment, which is often used in environments prone to dust and contamination, and consumer products, which need to be compact and have low power consumption.
TDK is able to meet high-precision sensing needs around the world with TMR sensors that have unparalleled high angle precision.

TDK’s TMR sensors are used in a wide range of applications including automobiles, which are becoming increasingly automated and electrified, industrial equipment, which is often used in environments prone to dust and contamination, and consumer products, which need to be compact and have low power consumption.

TDK is able to meet high-precision sensing needs around the world with TMR sensors that have unparalleled high angle precision.

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Today, robots are appearing everywhere in our daily lives and society. New types of robots are emerging one after another, such as service robots that provide customer service, security and cleaning in place of humans, and “companion” robots that behave like family members or pets. The natural, smooth movements seen in the latest robots are made possible by a combination of motors and sensors. In this article, we will take a closer look at the secrets of high-precision TMR sensors that are enabling the advancement of robots.

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