Magnetoresistive sensors aim at industrial and white goods

Honeywell has added to its line of magnetoresistive sensors.

Magnetoresistive sensors aim at industrial and white goods

Cryptically called the Standard Power Series, there are four devices in all, aimed at industrial, medical and white goods applications. The firm is thinking: flow sensing in air conditioning, anti-tamper detection in utility meters, RPM sensing in exercise equipment and door position detection, to name but a few.

The most sensitive operate at 11 Gauss max, “making the sensors among the most highly sensitive in their class for standard power applications,” said the Honeywell. “This creates larger air gaps between the sensor IC and the magnet and allows engineers to decrease the total cost of their designs by using smaller, less expensive magnets.”

Operation is omni-polar and over 3 to 24V and -40 to 85°C.

The operation threshold drifts little over the temperature range, and the open-collector output can pull 20mA down to 0.5V.

Take a look at the magnetoresistive sensor data sheet for the various operation orientations.

“The new Standard Power Series Sensor ICs provide alternatives to Hall-effect ICs at a time when rare earth magnet prices are high. They also are alternatives to reed switches when high reliability and durability are major considerations,” said Joshua Edberg, director of packaged sensors at Honeywell.

There are two sensitivities and two packages covered by four part numbers

  • Typically operate at 7G (11G max): SM351RT  (SOT-23) and SM451R (flat TO-92)
  • Typically operate at 14G (20G max): SM353RT  (SOT-23) and SM453R (flat TO-92)

Comments

2 comments

  1. Hi Steve
    I hadn’t spotted that folk were moving away from rare earth magnets, so thanks for the information.
    As I remember from the lectures of Professor Eric Laithwaite, switched reluctance motors are always heavier than permanent magnet motors (for a given power and speed rating) because the rotors can only be pulled and not pushed by the stator. That said, Dyson did a really neat high-speed SR motor for vacuum cleaners that ran at 100,000 rpm – a heck of a speed for a consumer item!!
    Any idea why MR is more sensitive than Hall?

  2. Interesting! MR technology never really seemed to take off, especially compared with some of the hall based sensors that are available.

    I have seen a Honeywell sensor that used MR in a two-part rotary sensor. As this article suggests, it seemed to use an array of MR sensors, where the MR sensor could also have been a hall cell.

    The desire to avoid rare earth magnets is becoming more common. I’ve seen electric motor designs change from permanent magnet rotors to a switched reluctance design in order to save on the relatively pricey rare earth magnets. Interesting to see it also drive a switch to MR instead of hall effect.

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