Estimation of resolution and contact force of a longitudinally vibrating touch probe sensor using lead zirconate titanate (PZT) thin-film vibrator

In this paper, the evaluation of the sensitivity, resolution, and contact force of a touch probe sensor device for higher sensitivity and low contact force is reported. Our goal in designing our touch probe sensor was to realize high-resolution, low-contact-force, wide-scanning-area up to mm scale square, and quick-scanning surface profile measurement. The sensitivity and resolution of our touch probe sensor were 2.0 × 10^-2 mV/nm and 2.4 nm, respectively. Although this resolution depends on the noise level, the noise level of the pre-amplifier circuit was much larger than that of the vibrator. By minimizing the noise of the circuit by using low-noise-type operational amplifiers, higher resolution up to 0.2 nm can be obtained. Although the contact force was estimated to be 25 μN under a 0.3 V_p-p driving voltage, it will be 300 nN when using a low-noise circuit.