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Hall Effect Finds Niche in Current Sensing
Technology saves money, reduces power consumption, eliminates bulk
Charles J. Murray, Senior Technical Editor -- Design News, July 14, 2008
The venerable Hall Effect sensor is gaining popularity these days in electrical current sensing applications, where it is sometimes replacing transformers and shunt resistors. There, it's helping engineers reduce power consumption, save money and eliminate bulk.
It's doing all that because its technology is simple, well-established and inexpensive. The Hall Effect, which refers to the potential difference on opposite sides of an electrical conductor, was discovered in 1879. It has since been used in applications ranging from automotive to industrial control, where it helps sense position, pressure and motion. In those applications, engineers often choose Hall Effect sensor packages because they're virtually immune to dust, dirt and moisture.
In the past few years, however, some vendors have begun to tailor their Hall Effect products for current sensing applications. Those products are finding a niche among engineers who don't want to “roll their own” or customize existing products for those applications.
As a result, suppliers of the current-sensing Hall Effect devices are finding that their products are being snapped up in a new breed of applications.
“We have customers making intelligent power strips who are very excited about ripping out their bulky transformers and replacing them with our current sensors,” says Mike Doogue, director of strategic marketing for Allegro MicroSystems Inc., a maker of sensors and integrated circuits (ICs).
Indeed, Doogue says he's seen Hall Effect sensors replace shunt resistors in a few space-constrained applications and has seen them replace transformers in white goods, industrial motor control and in a variety of automotive applications.
“In many motor control applications, material costs are sending motor prices through the roof,” Doogue says. “If you can make a motor smaller because you eliminate three big current transformers on each phase of the motor, then you can save on material costs.”
Here, we present two Hall Effect products — from Allegro and LEM — that offer solutions to engineers who need current-sensing technology.
“We've put in the extra features for current sensing,” Doogue says, “so the customers don't have to do it themselves.”
LEM's Dual-Range Automotive Sensor
LEM's DHAB dual-range automotive sensor is designed for current sensing in vehicle battery monitoring. Typically fixed to the battery cable of a car, DHAB's two cores allow it to be used for two separate current ranges — one between ±20 and ±80A and another between ±50 and ±600A. LEM says this setup enables full-range current measurements to be made in combination with accurate measurements of lower currents. DHAB's sealed housing also means no potting is required. Panel- and cable-mount versions are available.
Allegro's Automotive Grade Current Sensors
Allegro MicroSystems' ACS714 and ACS715 Hall Effect sensors are engineered for sensing of low ac and dc currents in automotive applications. Designed to operate in a full automotive temperature range (-40 to 150C), the new devices consist of low-offset linear Hall Effect sensor circuits with copper conduction paths located near the surface of the die. They provide low power losses and are contained in small, surface-mount SOIC8 packages. Both are also lead-free, except for RoHS-exempt solder balls.
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