Working principle selection

The basic form of motion of an object is translation and rotation. The translation of linear motion can also be turned into a form of rotation through a rack and pinion or a connecting rod. At present, most of the power sources we use are driving methods represented by rotating motors, so (high-precision) angle sensors (or angular displacement sensors) are in a very important basic position in automatic control. If the precise control from the rotation of the motor can be achieved, it will undoubtedly be of great significance to the field of automatic control technology.

Sensors are generally the core and key components of automatic control systems. For scientific research, the highest precision sensors are often selected when funding permits. If it is a product design, the optimal selection is the most optimal type that can not only meet the accuracy requirements of the system measurement but also achieve lower cost accounting. Therefore, the angle sensor selection is a systematic process, and the type selector is required to have a more comprehensive understanding of the problems you need to solve with the angle sensor, and have a preliminary estimated budget for various technical indicators, installation dimensions, and price costs.

How can we do a good job in the selection of angle sensors?

(1) According to the technical requirements of the measurement object, the basic selection is based on the different working principles of the angle sensor:

Classification of angle sensor principle:

1) Conductive film sub-potentiometer type: including carbon film, metal film, and conductive plastic film potentiometer with longer service life.

Features: The sliding contact gives the differential value of the input power voltage with the rotation of the sensor shaft. The conductive plastic has good wear resistance, stable temperature characteristics, and the service life is tender enough to meet the use under general conditions. The market price ranges from hundreds of yuan. low cost. However, the contacts exist, wear exist, and the service life is claimed to be ten million times. In many cases, inaccuracy often occurs in the second half to one year. In addition, the contact exists, the anti-vibration and impact performance is not good, and the applicability to industrial environments such as water and oil gas is poor. It needs to rely on external sealing treatment, which cannot fundamentally solve the problem.

2) Resolver (LVDT type) angle sensor: The resolver angle sensor uses the traditional electromagnetic induction effect to modulate the frequency of the alternating electric field through the differential coil winding and built-in magnetic materials, and then uses the single-chip microcomputer to process the angle measurement. The characteristic is that the original induction signal is the coil winding, the temperature application range is large, and the temperature stability is better; the frequency modulation resolution is higher, and the small angle measurement accuracy can reach the arc second level. The disadvantage is that the volume and weight are large, and it is difficult to achieve large-angle measurement. The sensor needs to be shielded inside, and the price is relatively high. The market price is more than four digits.

3) Optical angle sensor: It is an angle sensor represented by an optical encoder. It uses an optical encoder to detect light and dark stripes to achieve digital output angle detection. In addition, the use of multi-channel digital optical encoders can achieve absolute position and angle measurement. The optical encoder is also a non-contact signal sensing angle sensor, but due to the limitation of the optical path, the harsh working environment such as water, oil, vapor, and dust needs to be sealed to achieve angle detection. Incremental optical encoders cannot achieve absolute position measurement, especially when the power is off, only the starting point can be re-recorded or reset. But the price is moderate, and the domestic batch is a few hundred yuan; the price canon of multi-channel absolute position optical encoder is more than one thousand yuan.

4) Polarized light angle sensor: Using the relative rotation position change of two polarizers, the rotation angle is measured by the transmitted light intensity. This understanding principle can only measure angle changes less than 45 degrees, and is generally used for measurement in optical modulation systems or under special environmental conditions.

5) Traditional Hall device angle sensor: It uses a rotating magnetic field to cause changes in the output voltage signal of the Hall device to measure the rotation angle. The magnetic field rotates 360°, and the Hall device obtains a sinusoidal output signal. Approximately linear measurement can only be achieved in a limited interval. It is characterized by low price and is suitable for occasions where the measurement accuracy is not high, such as the torque control of electric bicycles.

6) Semiconductor magnetoresistive angle sensor: Use the rotating magnetic field to change the partial pressure of the differential semiconductor thin film magnetoresistor to achieve angle measurement. This principle is that the original output signal is known to be the largest, which can reach several volts. However, due to the incompatibility between the manufacturing process and contemporary integrated circuit technology, only the finalized products are used. The Japanese Midori company and individual domestic manufacturers also have corresponding products. The semiconductor substrate has a large temperature coefficient, and the use of temperature compensation in a wide temperature range is the technical crux of this type of angle sensor. Accurate temperature compensation needs to be performed sensor by sensor, resulting in higher costs.

7) The intelligent integrated magnetic-sensitive angle sensor uses MEMS technology to integrate the nano-magnetic cluster film material and the differential array magnetic-sensitive element, and non-contact senses the change of the rotating magnetic field. Magnetic sensitive elements can use array differential Hall devices, spin valve giant magnetoresistance, tunnel junction giant magnetoresistance and other sensitive elements with different physical effects. The system integrates a microprocessor (micro-computer), through software programming DSP processing, to achieve 360 ° Full-scale angle measurement.

Magnetic angle sensor has no contact, long life, high resolution, low temperature drift, excellent linearity, fine reset, high frequency response, multiple protections, anti-interference, vibration resistance and shock resistance, suitable for water, oil, gas, vibration, impact, etc. It is an ideal angle sensor with better cost performance in a harsh industrial environment. It is also the best product for the replacement of contact angle sensors (such as conductive plastic potentiometers).

okplazas.com's series of DWQT magnetic angle sensors, QXJ tilt angle sensors, high-precision digital angle sensors, CB magnetic encoders and other products, comprehensively compare the detection principles of various physical mechanisms, and aim at different applications and market needs , Developed a series of products ranging from low-cost and economical to high-precision and high-resolution angle sensors. Through program DSP processing, realize linearity correction, temperature compensation, standardization of given range output signal, digital filtering, zero setting, multi-stage different slope setting, analog voltage, current transmitter and various protection circuits, fault diagnosis and viewing Intelligent control such as door dog reset. okplazas.com has been committed to the innovation and development of magnetic sensors for 30 years, condensed hundreds of application cases, can provide users with practical angle sensor selection programs, consulting guidance, special product customization, and provide cost-effective, timely delivery, Reliable products, enjoy the support of a complete after-sales service system.

Magnetic angle sensor has no contact, long life, high resolution, low temperature drift, excellent linearity, fine reset, high frequency response, multiple protections, anti-interference, vibration resistance and shock resistance, suitable for water, oil, gas, vibration, impact, etc. In a harsh industrial environment, this feature is far superior to optical angle sensors, and it is also the best product for the replacement of contact-type conductive plastic potentiometers. The intelligent integrated magneto-sensitive angle sensor is the most cost-effective optional angle sensor on the market.