Magnetic speed and direction sensor works with bigger gaps

“By monolithically integrating our GMR technology with digital processing we’ve set a new standard for transmission speed sensing,” claimed Allegro business unit director Peter Wells. “ATS19580’s ability to reach formerly unachievable air gaps with the best vibration performance on the market simplifies the customers Speed Sensor integration.”

And what is that gap?

1.5 – 4.5mm is the answer, according to the data sheet – tested at 1000 rpm sensing a 120mm diameter 60 tooth ferromagnetic wheel known as ‘reference target 60-0’.

The device is a two-pin current output sensor operating from 4 to 24V. Through current is somewhere less that 8mA to indicate one logic state and somewhere over 12mA to indicate the other – although they can vary for various reasons, the two currents are always in the ratio 1.9:1. Up to -18V can be tolerated in reverse.

Inside the 2 pin SIP package is the GMR IC, a protection capacitor for EMC robustness and a back-bias magnet. The extra black bit on the leads is a molded lead-stabilising bar for robust shipping and ease of assembly.

Differential sensing is employed to reject interfering common-mode magnetic fields, and the built-in diagnostics detect failures that would impact output accuracy, providing coverage compatible with ASIL B (assessment pending).

Built-in EEPROM scratch memory offers traceability of the device throughout the IC’s product lifecycle.

ASIL reporting can be enabled or disabled as a product offering depending on the applications’ needs.

Direction is sensed by the order in which two internal sensors are triggered, and vibration is detected as multiple changes in target direction – two vibration output protocols are available. Read the data sheet for details.