GAS SENSOR WITH HEATER
A first embodiment of a disclosed breath analyzer detects a particular breath component in a breath sample. The analyzer includes a housing defining an interior cavity and having an inlet aperture for receiving the breath sample and an outlet aperture. A sensor is disposed within the cavity for sensing the component of the breath sample. An anemometer circuit is associated with the sensor and measures a rate of flow of the breath sample within the housing. The analyzer further includes a controller operatively connected to the sensor to receive breath component information sensed by the sensor.
1 . A breath analyzer for detecting a component in a breath sample, the analyzer comprising:
(a) a housing defining an interior cavity, the housing comprising an inlet aperture for receiving the breath sample and an outlet aperture;
(b) a sensor disposed within the cavity for sensing the component of the breath sample;
(c) an anemometer circuit associated with the sensor, the anemometer circuit measuring a rate of flow of the breath sample within the housing; and
(d) a controller operatively connected to the sensor to receive breath component information sensed by the sensor.
2 . The breath analyzer of claim 1 , wherein the anemometer circuit comprises a temperature control system integrally formed with the sensor, the temperature control comprising a resistive temperature device configured to heat the sensor to a predetermined temperature and to sense the temperature of the sensor
3 . The breath analyzer of claim 2 , wherein the sensor comprises a metal oxide deposited on a substrate.
4 . The breath analyzer of claim 3 , wherein the metal oxide comprises tungsten trioxide.
5 . The breath analyzer of claim 3 , wherein the substrate comprises aluminum oxide.
6 . The breath analyzer of claim 3 , wherein the temperature control system comprises a platinum metallization deposited on the substrate.
7 . The breath analyzer of claim 6 , wherein the metal oxide is deposited on a first side of the substrate and the platinum metallization is deposited on a second side of the substrate.
8 . The breath analyzer of claim 2 , wherein the temperature control system comprises a closed-loop control circuit selectively controlling the resistive temperature device.
9 . The breath analyzer of claim 8 , wherein the control circuit comprises a bridge circuit operably connected to an operational amplifier.
10 . The breath analyzer of claim 9 , wherein the bridge circuit comprises four resistors, the resistive temperature device acting as one of the resistors.
11 . The breath analyzer of claim 8 , wherein the control circuit comprises a processor controlling a resistive divider, resistive divider comprising the resistive temperature device connected in series with a shunt resistor.
12 . The breath analyzer of claim 11 , wherein the processor controls the voltage provided to the resistive divider according to a voltage drop across the resistive divider.
13 . A breath analyzer for detecting a component in a breath sample, the analyzer comprising:
(a) a housing defining an interior cavity, the housing comprising an inlet aperture for receiving the breath sample and an outlet aperture;
(b) a metal oxide sensor disposed within the cavity for sensing the component of the breath sample;
(c) a temperature control system integrally formed with the sensor, the temperature control system comprising a metal resistor having a positive temperature coefficient, the metal resistor being configured to heat the sensor to a predetermined temperature and to sense the temperature of the sensor, wherein a closed-loop control circuit selectively controls the metal resistor, the metal resistor being integrally formed with the closed-loop control circuit, the closed-loop control circuit being configured to measure a rate of flow of the breath sample within the housing; and
(d) a controller operatively connected to the sensor to receive breath component information sensed by the sensor.
14 . The breath analyzer of claim 13 , wherein the control circuit comprises a bridge circuit operably connected to an operational amplifier.
15 . The breath analyzer of claim 14 , wherein the bridge circuit comprises four resistors, the metal resistor acting as one of the resistors.
16 . The breath analyzer of claim 13 , wherein the control circuit comprises a processor controlling a resistive divider, resistive divider comprising the metal resistor connected in series with a shunt resistor.
17 . The breath analyzer of claim 16 , wherein the processor controls the voltage provided to the resistive divider according to a voltage drop across the resistive divider.