Piezoelectric sensor Q-loss compensation
US4788466A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 9, 1987 |
| Grant date | Nov 29, 1988 |
| Priority date | — |
| Expiry date | Nov 9, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2291/0256
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
There is disclosed Q-loss compensation apparatus for a piezoelectric sensor such as a quartz crystal microbalance or other resonant vibratory device wherein the vibration amplitude of the device is controlled by negative feedback in a manner to obviate the effect of energy loss associated with viscous damping of a large liquid drop on the quartz crystal face serving as an environment for an experiment to measure mass deposited on the crystal face. The specific apparatus includes an oscillator circuit for the vibratory device in which two generally similar variable gain amplifiers provide the regenerative feedback for maintaining oscillation. The negative feedback amplitude control circuit serves to maintain constant the output from the variable gain amplifier following the quartz crystal in the oscillator loop, and it thus maintains at a near constant value the product of the crystal vibration amplitude and the square root of the total gain in the oscillator loop. This results in stable oscillation of the quartz crystal with little influence from changing conditions such as temperature, viscosity of the fluid, evaporation of the fluid, etc., at the same time producing a linear freq…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.