How to measure the CHUM ultrasonic frequency

ASTM D6760 standard requires that "The transmitter probe shall generate an ultrasonic pulse with a frequency of 30,000 Hz to 60,000 Hz." The CHUM nominal frequency is around 55KHz, but how can we verify that without expensive lap equipment? The good news is that we already have all the equipment that we need in our hands! The CHUM

Here is how

1. Open any pile and profile

2. Select [FAT]

3. Pick any good, strong pulse

4. Click on two peaks, 10 cycles apart (We use 10 to improve accuracy)

5. Write down the FAT value for each peak

6. Subtract and divide the result by 10 to get a single period duration in uSec.

7. Divide 1e6 by the result you got to get the actual frequency in KHz.

Here is an example