Object position/presence sensor and method for detecting object position or presence

An image forming device, comprising:

• an image forming engine;
• a recording medium transport system that supplies a recording medium to and removes the recording medium from the image forming engine;
• and
• at least one object sensor that detects at least one of the position, a presence or an absence of the recording medium in the paper transport system, the object sensor including:
• a housing defining an object passage through which the recording medium is movable;
• a fluid source that provides a fluid flow across the object passage;
• a sensor device that generates a first signal indicative of an amount of a property at a first time, the property being dependent on an amount of the fluid flow the first signal indicative of a first amount of the fluid flow;
• a sensor device that generates a second signal indicative of an amount of a property at a second time, the property being dependent on an amount of the fluid flow, the second signal indicative of a second amount of the fluid flow;
• and
• a comparator that compares the first signal and the second signal to determine at least one of the position, the presence or the absence of the recording medium in the paper transport system,
• wherein, when the recording medium is in an obstructing position relative to the fluid source and the sensor device, the sensed fluid flow decreases.

A method of sensing at least one of a position, a presence, or an absence of a moving object in an object passage, the method comprising:

• generating a flow of fluid across the object passage;
• sensing a first value of a property at a first time, the property dependent on an amount of fluid flow, the first value indicative of a first amount of the fluid flow;
• sensing a second value of the property at a second time, the second value indicative of a second amount of the fluid flow;
• and
• comparing the first value and the second value to determine at least one of the position, the presence or the absence of the object relative to the object passage.