Patent ID: 7187282

Claim:
An apparatus for sensing an object, the apparatus comprising: a field generating circuit, providing a sensing field signal having a sensing field frequency; an antenna, in electrical communication with the field generating circuit, the sensing field frequency being modified by a capacitive coupling between the antenna and the object when the object is proximate to the antenna; a frequency comparison circuit, providing a frequency comparison of the sensing field frequency with a reference value to determine if the sensing field frequency is greater or less than the reference value, and further operable to provide a difference value that corresponds to a difference between the sensing field frequency and the reference value a reference value circuit, providing the reference value to the frequency comparison circuit for the frequency comparison, and operational to increment the reference value if the sensing field frequency is greater than the reference value, and to decrement the reference value if the sensing field frequency is less than the reference value; a threshold compare circuit, receiving the difference value and comparing the difference value with a threshold value, the threshold compare circuit providing a detect signal if the difference value is greater than the threshold value; and a condition sensor providing a condition signal, the threshold value being adjustable according to the condition signal.