Answer:
Hertz can be measured using a frequency counter, multimeter, or oscilloscope. Some multimeters have basic frequency counters that only work for electrical signals. To measure radio frequency, a proper frequency counter or oscilloscope with RF inputs is required.
Weak radio signals usually need some amplification and filtering to be measured. This requires the signal to be passed through additional devices before reaching the counter. To measure the frequency of mechanical vibrations, a transducer is required to convert them into electrical signals.