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Frequency & Phaseshift

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 measuring ranges.

Accuracy & Current in Two Measurement Ranges

PeriodsFreqResolution (1 measure-ment per second)current*Accuracy (sampling1000 measurements per sec)current*
mes. range2min60ns16.7MHz0.5%400nA0.015%550uA
max100ms10Hz10-7%5uA
mes. range1min3ns333MHz4%400nA0.11%550uA
max6.7us150KHz0.05%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