Speed sensors insensitive to EMI
6 February 2008
Analogue, Mixed Signal, LSI
New speed sensor technology for industrial electric vehicles has been developed by SKF to cope with the harsh environmental demands created by the switch to more powerful, compact AC motor designs.
The growing trend towards replacing DC motors with AC designs is resulting in new challenges for designers of mechatronics solutions in control and sensing applications.
While there are space-savings and material cost reductions in adopting more compact and powerful AC drive motors, the greater compactness of motor design means that all the related components such as the electronics, bearings etc, are closer together and have to exist and perform in an even more demanding environment. For certain components such as the sensor electronics, the increasingly harsh electromagnetic and physical environments can be a real issue.
The main issue is that the existing sensor bearing technology employing Hall Effect devices, used mainly to detect the speed, direction and position of the drive shaft, cannot operate optimally or as expected because of interference by the strong magnetic fields generated by the higher motor currents (between 600 and 800 A) of these AC motors.
SKF has developed a new generation of speed sensors for electric AC motors that are said to be insensitive to the effects of strong magnetic environments. As importantly, the sensor can be integrated into the bearing design, continuing the general trend towards increased component integration and 'plug-and-play' solutions for electric vehicle systems.
The new motor encoder unit, designated the BMH series, uses an inductive microcoil technology, where two arrays incorporating inductive microcoils sense electromagnetic (EM) pulses that are bounced off a moving metallic target wheel that rotates with the bearing inner ring. The microcoils transform the EM signal into current, which is then converted into a voltage by a Schmitt Trigger that produces the pulses which are directly related to the speed of rotation. The signal created is clearly detectable and separable from any background noise and provides a versatile signal output.
One of the attributes of this sensing system is that it is valid for extremely low speeds and can provide accurate measurements over the range from zero up to about 20 000 rpm. Many other speed-sensing techniques have difficulty in accurate measurements at very low speeds. Another feature of this high performance motor encoder unit is its ability to work at ambient temperatures up to 150°C.
For more information visit www.skf.com
Further reading:
High-speed PIN diode
Altron Arrow
Analogue, Mixed Signal, LSI
Vishay’s new high-speed Silicon PIN diode is able to detect both visible and near infra-red radiation over a wide spectrum range from 350 to 1100 nm.
Read more...
Analogue front end for sensor measurements
Electrocomp
Analogue, Mixed Signal, LSI
The NJU9103 AFE from Nisshinbo is a tiny analogue front end, with a 16-bit resolution ADC and up to 512 x signal amplification from the programmable gain amplifier.
Read more...
Single-channel software configurable I/O
Altron Arrow
Analogue, Mixed Signal, LSI
These use cases of the AD74115H include analogue output and input, digital output and input, resistance temperature detector (RTD), and thermocouple measurement capability.
Read more...
Current-sense amplifier with PWM rejection
Altron Arrow
Analogue, Mixed Signal, LSI
Analog Devices’ AD8410A is a high voltage, high bandwidth current-sense amplifier that features an initial gain of 20 V/V and a 2,2 MHz bandwidth.
Read more...
Combining a LPF and ADC driver for a 20 Vp-p signal
Altron Arrow
Analogue, Mixed Signal, LSI
A mixed-signal ADC driver circuit’s optimum performance depends on multiple variables: the driver’s settling time, the RC filter’s time constant, driving impedance, and the ADC sampling capacitor’s kickback current, all interact during acquisition time and contribute towards sampling errors.
Read more...
Pressure sensor with NextNav certification
EBV Electrolink
Analogue, Mixed Signal, LSI
STMicroelectronics’ LPS22DF pressure sensor has received a NextNav certification, which guarantees performance and reliability for geolocation and other types of applications.
Read more...
Reference design for Raspberry Pi analogue I/O
Analogue, Mixed Signal, LSI
Analogue Devices has published a reference design for ±10 V analogue input and ±15 V analogue output for Raspberry Pi platforms.
Read more...
Multi-zone distance sensor with 90° field of view
Avnet Silica
Analogue, Mixed Signal, LSI
STMicroelectronics has revealed a new FlightSense multi-zone distance sensor, with 90° field of view, to bring lifelike situational awareness to applications like home automation, computers, robots, and smart equipment.
Read more...
Six-axis IMU with Qvar sensing channel
Altron Arrow
Analogue, Mixed Signal, LSI
The LSM6DSV16X from STMicroelectronics is a high-performance, low-power six-axis IMU, featuring a three-axis digital accelerometer and a three-axis digital gyroscope.
Read more...
Bidirectional current-sense amplifier with PWM
RS South Africa
Analogue, Mixed Signal, LSI
The MAX49925 from Analogue Devices is a bidirectional current-sense amplifier (CSA) with an input common-mode range that extends from -40 to 76 V, making it suitable for 48 V HEV applications where there are large automotive transients.
Read more...
printer friendly version