An embodiment of the invention relates to a sampling circuit comprising at least one clock, a reference trace, a sensor trace adapted to be connected to a sensing element, and a device to measure a length of delay between a reference signal transmission time of a reference signal transmitting through the reference trace and a sensed signal transmission time of a sensed signal transmitting through the sensor trace, wherein the length of delay is determined by counting the number of burst tones occurring during the length of delay.