Field Adjustable Length Magnetic Sash Position Sensor

circuit board

This product is a low cost field trimmable hall effect sensor strip for the application of measuring door sash position in fume hoods. A voltage output is available that is proportional to the percent opening of a door. The sensor strip is paired with an opposing magnetic strip. The magnets are slid over the sensor board strip which changes the magnetic field coverage. The range of the output voltage is self calibrating from zero to full scale no matter what size the measurement strip is trimmed to. Trimming to fixed lengths is accomplished using an ordinary scissors.

With this sensor the surface area opened to the outside of the fume hood can calculated by an attached controller. The controller uses this information, and measured airflows to controls airflow to automatically maintain fixed pressure differences no matter the door position.

Functional electronics for all the facets of this system have been developed. That is circuit design, and board layout. It can operate over a range of input voltages.