apsonic Handheld ultrasonic Frequency Tester. The Frequency Sniffer works with an integrated non-contact Probe. The Frequency Sniffer is very handy and fits perfectly in the Pocket of your Service People. The Frequency Sniffer can check the Frequency of Converters, Boosters, and Horns when they are activated by an Ultrasonic Generator. The Measuring Distance varies with the Amplitude you apply to the Vibrating System. For a 20.000 kHz, 1000 W, Generator with 1:2 Booster, the minimum Distance is 1000mm (39.37").