The OHB900 consists of a Hall-effect sensor similar to the OH180U and a rare earth magnet mounted in a low-cost plastic housing. The magnet produces optimum magnetic flux at the Hall-effect sensor location. The sensor has an open collector transistor output, which is activated when the slot is open. When the slot is blocked by a ferrous material that reduces the magnetic flux density at the Hall-effect sensor location, the open collector output transistor switches off. The device provides up to 25 mA of sink current. Output characteristics are constant at switching frequencies from DC to over 200 kHz.
The Uni-Polar turns on with a (logic level “0”) after a sufficient magnetic field from the south pole of a magnet approaches the symbolized face of the device (Operating Point) and turns off (logic level “1”) after the magnetic field reached a minimum value. This feature makes these sensors ideal for applications in non-contact switching operations.