Fast, high sensitivity dewpoint hygrometer
US5739416A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 18, 1996 |
| Grant date | Apr 14, 1998 |
| Priority date | — |
| Expiry date | Sep 18, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N25/68
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A dewpoint/frostpoint hygrometer that uses a surface moisture-sensitive sensor as part of an RF oscillator circuit with feedback control of the sensor temperature to maintain equilibrium at the sensor surface between ambient water vapor and condensed water/ice. The invention is preferably implemented using a surface acoustic wave (SAW) device in an RF oscillator circuit configured to generate a condensation-dependent output signal, a temperature sensor to measure the temperature of the SAW device and to distinguish between condensation-dependent and temperature-dependent signals, a temperature regulating device to control the temperature of the SAW device, and a feedback control system configured to keep the condensation-dependent signal nearly constant over time in the presence of time-varying humidity, corrected for temperature. The effect of this response is to heat or cool the surface moisture-sensitive device, which shifts the equilibrium with respect to evaporation and condensation at the surface of the device. The equilibrium temperature under feedback control is a measure of dewpoint or frostpoint.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.