Tongue rate monitor
A tongue frequency meter (also resonance frequency meter ) is an electromechanical or mechanical measuring device for determining the frequency of an alternating voltage or a vibrating (rotating) component. It differs from other digital and analog frequency meters in its mode of operation (several flexural transducers , each of which individually resonate ) and in its limited measuring range .
functionality
A tongue frequency meter works according to a deflection measuring method . A sheet iron comb is used for the display, the tines of which are matched to natural frequencies of twice the frequency to be measured due to their different lengths . An electromagnet is attached above this, which is controlled by the alternating voltage to be measured and thereby generates an alternating magnetic field . The periodic magnetic force, which is independent of the polarity of the magnetic field, excites the tongues to oscillate, the deflection being greatest at the prong where resonance occurs. The associated frequency can be read from a scale. If two adjacent prongs are strongly deflected, the correct frequency in between must be estimated.
With purely mechanical tongue frequency meters, the vibration (structure-borne sound) of the object to be measured is displayed through mechanical coupling.
commitment
In the past, reed frequency meters were usually used to determine the tolerance of the mains frequency or other low-frequency voltages, since they can usually only display a small frequency range. Depending on the frequency and possible deviation, their measuring range is , for example, 50 Hz or 60 Hz ± 2 ... 6 Hz for mains frequency . Compared to pointer frequency meters , they usually achieve higher accuracy and resolution and can also be read better in this range.
Tongue frequency meters were manufactured, for example, for center frequencies of 25 (telephone ringing voltage ), 50 or 60 (typical mains frequencies) or 400 Hz (aircraft electrical system ). In practical applications, electromechanical tongue frequency meters have been replaced by electronic frequency counters with digital displays, which can offer not only easier reading but also a higher frequency resolution.
Tongue frequency meters were also used to check mechanical vibrations of a component (for example the speed based on an imbalance). Here the vibration is directly coupled mechanically.
literature
- F. Hillebrand, R. Jäger, M. Schenkel, K. Schmiedel, W. Steinhaus, R. Vieweg: Starkstrommeßtechnik: A manual for laboratory and practice . Verlag von Julius Springer, Berlin 1933, ISBN 978-3-642-99386-2 , chapter frequency meter and frequency measurement, p. 134-138 (reprint 2013).
Individual evidence
- ^ Otto Lueger : Lexicon of the entire technology and its auxiliary sciences . 2nd Edition. Deutsche Verlagsanstalt, Stuttgart and Leipzig 1920 ( zeno.org [accessed on January 21, 2020] encyclopedia entry “measuring instruments, electrotechnical”).