FREQUENCY & PHASESHIFT

In many sensory 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

Periods .       Freq Resolution
(1 measure-ment per second)
current*Accuracy
(sampling1000 measurements per sec)
current*
mes. range2   min  60ns 16.7MHz        0.5%400nA .          0.015%550uA
max100ms  10Hz         10-7%5uA
mes. range1min3ns    333MHz        4%400nA0.11%
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