[FAQ] Sensors in Cooktops

Good question. Traditionally mechanical dials have been used but appliance manufacturers are now moving to electronic controls because of higher reliability. So, yes, Hall-effect sensors are in use more today and will be used even more in the future. Essentially any piece of electronic equipment that has moving parts has the potential to use a position sensor. Below is a use case where Hall-effect sensors are great for rotary dials or knobs.

Use case: Angle measurement for rotary dial or knob

In the graphic shown below, the Hall-effect sensor is used to detect the angle of the knob/dial by using a dipole magnet embedded within the knob. If using a 3D sensor, not only can the device be able to detect the angle but also the downward push that is very common in many applications.

When calculating the angle measurements of rotating shafts, on-axis measurements (where the sensor is directly beneath or above the rotating magnet) provide the most accurate angle measurements given that equivalent magnitude field vectors are produced. In the case of the control knob shown below, however, an on-axis implementation is not feasible because the shaft is obstructing the placement of the sensor. For this implementation, a Hall-effect sensor with gain correction is needed. If one magnetic field vector is slightly attenuated more than the other simply because of the placement, gain correction allows for the attenuated signal to be made equivalent in magnitude. Consequently, the angle error is greatly reduced.

Recommended Products:

Device	Data Sheet	Description	System-Level Benefits
TMAG5273		Low-power linear 3D Hall-effect sensor with I²C interface	·      Low power on-axis and off-axis angle measurement capability. ·      Temperature compensation for various magnet types enabling higher accuracy. ·      On-board angle calculation engine relieving the MCU from this task.

Tools and Resources:

• Angle detection TIPL video
• Absolute angle measurement for rotational motion app note
• Angle measurement with multi-axis linear Hall-effect sensors app note
• Angle calculation methods
• Achieving highest system angle sensing accuracy