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.
| 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 |
| max | 100ms | 10Hz | 10-7% | 5uA | |||
| mes. range1 | min | 3ns | 333MHz | 4% | 400nA | 0.11% | |
| 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