High sensitivity real-time NVR monitor

• US 5,661,226 A
• Filed: 11/09/1995
• Issued: 08/26/1997
• Est. Priority Date: 07/22/1993
• Status: Expired due to Fees

• Current Assignee: Femtometrics, Inc. (BAE Systems Plc)
• Original Assignee: Femtometrics, Inc. (BAE Systems Plc)
• Inventors: Chuan, Raymond L., Bowers, William D.
• Primary Examiner(s): BROCK, MICHAEL J
• Application Number:
  US08/554,893
• Time in Patent Office: 656 Days
• Field of Search: 73/24.01, 73/24.05, 73/24.06, 73/31.05, 73/31.06, 310/313 R, 310/313 B, 310/313 D
• US Class Current: 73/24.01
• CPC Class Codes: G01N 2291/014 Resonance or resonant frequency
• CPC Class Codes: G01N 2291/0212 Binary gases
• CPC Class Codes: G01N 2291/0256 Adsorption, desorption, surface mass change, e.g. on biosensors
• CPC Class Codes: G01N 2291/0422 Shear waves, transverse waves, horizontally polarised waves
• CPC Class Codes: G01N 2291/0423 Surface waves, e.g. Rayleigh waves, Love waves
• CPC Class Codes: G01N 2291/0426 Bulk waves, e.g. quartz crystal microbalance, torsional waves
• CPC Class Codes: G01N 29/022 Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices microdevices per se B81B
• CPC Class Codes: G01N 29/22 Details , e.g. general constructional or apparatus details
• CPC Class Codes: G01N 29/326 compensating for temperature variations
• CPC Class Codes: H03H 9/25 Constructional features of resonators using surface acoustic waves devices for manipulating acoustic surface waves in general G10K11/36

Abstract

A real time non-volatile residue (NVR) monitor, which utilizes surface acoustic wave (SAW) resonators to detect molecular contamination in a given environment. The SAW resonators operate at a resonant frequency of approximately 200 MHz-2,000 MHz which enables the NVR monitor to detect molecular contamination on the order of 10^-11 g-cm^-2 to 10^-13 g-cm². The NVR monitor utilizes active temperature control of (SAW) resonators to achieve a stable resonant frequency. The temperature control system of the NVR monitor is able to directly heat and cool the SAW resonators utilizing a thermoelectric element to maintain the resonators at a present temperature independent of the environmental conditions. In order to enable the direct heating and cooling of the SAW resonators, the SAW resonators are operatively mounted to a heat sink. In one embodiment, the heat sink is located in between the SAW resonators and an electronic circuit board which contains at least a portion of the SAW control electronics. The electrical leads of the SAW resonators are connected through the heat sink to the circuit board via an electronic path which prevents inaccurate frequency measurement.

Claims

1. An apparatus for detecting contamination, comprising:

a heat sink having opposing sides;

a detection SAW resonator in thermal contact with one side of said heat sink;

SAW control electronics, at least a portion of said SAW control electronics being in proximity to the other side of said heat sink, said portion of said electronics being electrically connected to said SAW resonator along an electrical path through said heat sink; and

wherein there is no thermoelectric element in direct physical contact with said SAW resonator.

2. The apparatus of claim 1, wherein said electrical path is no more than 0.25 inches in length.

3. The apparatus of claim 1, wherein said electrical path is between approximately 0.1 inches and approximately 0.2 inches in length.

4. The apparatus of claim 1, wherein said SAW resonator resonates at a frequency of approximately 200 MHz-2,000 MHz.

5. The apparatus of claim 1, wherein said heat sink is L-shaped.

6. The apparatus of claim 5, additionally comprising a thermoelectric element in thermal contact with said heat sink, and a radiator in thermal contact with said thermoelectric element.

7. The apparatus of claim 5, additionally comprising a radiator and a thermoelectric element which heats and cools said heat sink, said radiator in thermal contact with said thermoelectric element, wherein said thermoelectric element and said radiator are mounted on one leg of said L-shaped heat sink, said SAW resonator is mounted to another leg of said L-shaped heat sink and said SAW control electronics are mounted proximal to said another leg of said L-shaped heat sink.

8. The apparatus of claim 1, additionally comprising first and second enclosures, said enclosures being separate from each other and being operatively connected to each other to transfer signals therebetween, one of said enclosures comprising a monitor enclosure which houses said SAW resonator, the other of said enclosures comprising a support enclosure which houses support devices, one of said support devices comprising a power supply.

9. The apparatus of claim 8, additionally comprising a duct between said first and second enclosures for drawing fluid from said monitor enclosure to said support enclosure.

10. The apparatus of claim 1, wherein said portion of said SAW control electronics in proximity to the other side of said heat sink comprises oscillator electronics.

11. The apparatus of claim 1, wherein another portion of said SAW control electronics is located remotely from said SAW resonator.

12. The apparatus of claim 11, wherein said another portion of said SAW control electronics comprises signal processing electronics.

13. The apparatus of claim 11, wherein said another portion of said SAW electronics is connected to said portion of said SAW control electronics in proximity to the other side of said heat sink by an electrical conductor.

14. The apparatus of claim 11, wherein said another portion of said SAW electronics is connected to said portion of said SAW control electronics in proximity to the other side of said heat sink by fiber optics.