Patent ID: 9500726
Filing Date: 2016-11-22
CPC Classification: G01R

Claim Text:
1. An NMR probe head having an RF resonant circuit, the probe head comprising: at least one capacitor that is part of the RF resonant circuit, said capacitor having a dielectric, which at least partially surrounds a cavity, said dielectric being connected to at least one electrode at which an electrical potential of said capacitor can be picked off, wherein a capacitor piston with an electrically conductive surface is disposed in said cavity within said dielectric; a piezo-electric actuator disposed outside said cavity as an extension of an axis of said capacitor piston; a piston operating rod mechanically connected to said piezo-electric actuator and cooperating with said capacitor piston to move said capacitor piston in said cavity; and a sliding bush mechanically connected to said dielectric, said sliding bush having a through-hole through which said piston operating rod extends, wherein said piston operating rod moves said capacitor piston linearly in response to application of a sawtooth-waveform electric voltage to said piezo-electric actuator to tune said capacitor, said sliding bush thereby applying braking friction to said piston operating rod during linear displacement of said capacitor piston in such a fashion that said piston operating rod only slides through said through-hole during steep edges of said applied sawtooth voltage.