Frequency and Phase Shift

In many sensoric applications the value of interest (capacity, resistance, weight, density, pressure ...) is converted to a frequency change or phase shift. Typical examples are capacitive or inductive proximity sensors or piezoelectric weighing cells.

Take as an example the frequency measurement with the help of the TDC-GP1: connect the frequency signal (should be TTL) simultaneously to the start and stop inputs of the GP1 - that's all! You directly measure the period. Depending on the accuracy requested, this can be realized with lowest current consumption - ideal for battery driven equipment. The table shows some typical values for accuracy and current consumption in the two measering ranges.

• Laser distance
• Ultrasonic flowmeter
• Ultrasonic density meter
• Ultrasonic thickness meter
• Magnetostrictive Positioning
• Drift chambers
• Frequency and Phaseshift

		Periods	Frequency	Resolution (1 measurement per second)	current *	Accuracy (Sampling 1000 measurements p.sec. )	current*
mes.range2	min	60ns	16,7MHz	0,5%	400nA	0,015%	550uA
	max	100ms	10Hz	10-7%	5uA
mes.range1	min	3ns	333MHz	4%	400nA	0,11%	550uA
	max	6,7us	150KHz	0,05%	400nA
				1 LSB = 120ps	*calibration clock active only during measurement

In the same way it's possible to measure the jitter of a frequency signal or the phase shift between two signals - with up to 2.5 million measurements per second