A measuring device (u) for measuring parameters of a piezoelectric crystal onto which a thin film of material is deposited, comprising: - said piezoelectric crystal with two spaced-apart electrodes (2, 2'), onto which crystal said film of material is deposited, said crystal for instance having a fundamental resonance frequency when no film is deposited thereon in the range from 1 MHz to 100 MHz, more particularly in the range from 2 MHz to 7 MHz, most particularly in the range from 5 MHz to 6 MHz, said crystal in particular being an AT cut quartz crystal; - a frequency generator adapted to generate an oscillator signal at a specified output frequency; - a measuring amplifier adapted to apply said oscillator signal as a drive signal to one of said electrodes (2, 2') of said crystal and to provide a crystal output signal in response to said drive signal; - a quadrature demodulator adapted to down convert said crystal output signal and to provide an in-phase output signal and a quadrature output signal, said in-phase and quadrature output signals in particular being digital signals; - a computation unit adapted to determine one or more parameters of said crystal, in particular when said film of material is deposited on said crystal, based on said in-phase output signal and said quadrature output signal, in particular at a plurality of different frequencies, for instance at a fundamental resonance frequency of said crystal, at one or more harmonic resonance frequencies of said crystal, at one or more anharmonic resonance frequencies of said crystal, or at one more frequencies above or below said fundamental resonance frequency of said crystal, wherein said parameters of said crystal are: - a crystal series resistance (R m); - a crystal series capacitance (C m); - a crystal series inductance (L m); - a parallel admittance (Y 0); - a crystal quality factor, characterised in that the device (u) further comprises: - a compensation unit adapted to numerically compensate said parallel admittance (Y 0). - said piezoelectric crystal with two spaced-apart electrodes (2, 2'), onto which crystal said film of material is deposited, said crystal for instance having a fundamental resonance frequency when no film is deposited thereon in the range from 1 MHz to 100 MHz, more particularly in the range from 2 MHz to 7 MHz, most particularly in the range from 5 MHz to 6 MHz, said crystal in particular being an AT cut quartz crystal; - a frequency generator adapted to generate an oscillator signal at a specified output frequency; - a measuring amplifier adapted to apply said oscillator signal as a drive signal to one of said electrodes (2, 2') of said crystal and to provide a crystal output signal in response to said drive signal; - a quadrature demodulator adapted to down convert said crystal output signal and to provide an in-phase output signal and a quadrature output signal, said in-phase and quadrature output signals in particular being digital signals; - a computation unit adapted to determine one or more parameters of said crystal, in particular when said film of material is deposited on said crystal, based on said in-phase output signal and said quadrature output signal, in particular at a plurality of different frequencies, for instance at a fundamental resonance frequency of said crystal, at one or more harmonic resonance frequencies of said crystal, at one or more anharmonic resonance frequencies of said crystal, or at one more frequencies above or below said fundamental resonance frequency of said crystal, wherein said parameters of said crystal are: - a crystal series resistance (R m); - a crystal series capacitance (C m); - a crystal series inductance (L m); - a parallel admittance (Y 0); - a crystal quality factor, - a crystal series resistance (R m); - a crystal series capacitance (C m); - a crystal series inductance (L m); - a parallel admittance (Y 0); - a crystal quality factor, characterised in that the device (u) further comprises: - a compensation unit adapted to numerically compensate said parallel admittance (Y 0). - a compensation unit adapted to numerically compensate said parallel admittance (Y 0).