Impedance spectroscopy based systems and methods
One aspect of the invention provides a device that non-invasively determines the concentration of a substance in a target. The device includes a first electrode, a measuring circuit, and a data processor. In one embodiment of the device, the first electrode can be electrically insulated from the target, e.g., a cover layer of insulating material covers the first electrode.
1. A method for managing a process involving a specimen, the method comprising:
arranging a first electrode at the specimen, wherein the first electrode is electrically insulated from the specimen;
receiving a modulated electrical voltage signal at the first electrode to generate a modulated field in the specimen;
measuring at least one parameter depending on a response of the specimen to the field;
determining a concentration of a substance in the specimen based at least in part on the measured parameter; and
controlling an aspect of the process based at least in part on the determined concentration.
2. The method of claim 1 wherein controlling an aspect of the process comprises controlling a valve based at least in part on the determined concentration.
3. The method of claim 1 wherein the method further comprises arranging a second electrode at the specimen and wherein the modulated electrical voltage generates a modulated field between the first and the second electrode.
4. The method of claim 3 wherein the second electrode is in electric contact with the specimen.
5. The method of claim 3 wherein the method further comprises measuring a temperature of the specimen and using the temperature in the determination of the concentration.
6. The method of claim 1 wherein the modulated electrical voltage signal is a sine wave.
7. The method of claim 6 wherein the modulated electrical voltage signal has a frequency between 10 MHz and 2 GHz.
8. The method of claim 1 wherein the method further comprises arranging an antenna electrode at the specimen in proximity to the first electrode and wherein the response of the specimen is measured by measuring a signal transmitted from the first electrode to the antenna electrode.
9. The method of claim 1 wherein the substance is glucose.
10. The method of claim 1 wherein the specimen is a living body.
11. The method of claim 1 wherein the determining the concentration comprises using calibration data to convert the parameter to the concentration.
12. The method of claim 1 wherein the first electrode forms part of a resonant circuit having a resonance frequency and wherein the resonant circuit is operated substantially at the resonance frequency.
13. The method of claim 12 wherein the resonant circuit is at least part of a tank circuit of an active oscillator and wherein the parameter is one of an amplitude and a frequency of a signal generated by the oscillator.
14. The method of claim 1 wherein receiving a modulated voltage comprises receiving a frequency sweeped modulated voltage wherein the frequency is swept from a frequency below the resonance frequency to a frequency above the resonance frequency.
15. The method of claim 1 wherein the substance is an alcohol.
16. The method of claim 1 wherein the specimen is a salt solution.
17. The method of claim 1 wherein the substance is a salt.