Andros Analyzers Incorporated

Andros Anlayzers Incorporated

Raymond E Rogers

Robert E Passaro

Kevin G Williams

George K Parnoff

Craig J Griffith

An arrangement for ensuring the stability of the set point for a gas analyzer is disclosed. The set point control circuit utilizes an amplifier which is alternately switched between a reference voltage and a sensor signal to provide a signal to a processor representing the reference signal and the sensor signal. The processor compares the two signals and adjusts the heater associated with the sensor to provide a stable set point for the gas analyzer. The arrangement eliminates the need for precision resistors within the set point control circuit and therefore significantly reduces the cost of the circuitry.

Set point control circuit for an infrared gas analyzer

A gas analyzer is described comprising a sample cell for containing a gas mixture to be analyzed, a source for producing and directing infrared energy through the sample cell, a rotary filter wheel having at least one filter thereon for passing infrared energy limited to a wavelength band within the characteristic absorption band of a predetermined gas and having a dark level region substantially opaque to infrared energy, a drive for supporting and rotating the filter wheel to successively interpose the filter and the dark level region between the source and the sample cell in the path of the infrared energy directed by the source, a detector for detecting infrared energy passing through the sample cell and producing an electrical signal representative thereof, and a signal processor connected to the detector for producing an output indicating the concentration of the predetermined gas in the sample cell by comparing the electrical signals produced by the detector with the filter positioned in the infrared energy path and with the dark level region positioned in the infrared energy path. The dark level region has a substantially fully reflective surface oriented toward the sample cell when positioned in the infrared energy path whereby infrared energy impinging thereon is reflected.

Digital anesthetic agent analyzer

Automatic zeroing apparatus zeroes an infrared gas analyzer automatically upon the occurrence of preselected conditions to indicate zero in the absence of absorption of infrared radiation by a gas mixture being analyzed. The gas analyzer has a sample cell for containing a gas mixture to be analyzed. Infrared radiation directed through the sample cell is detected at a preselected wavelength to produce a detection signal. A signal processor outputs a signal systematically related to the difference between the detection signal and a reference signal. For zeroing the sample cell is filled with gas substantially nonabsorbent of infrared radiation at the respective characteristic wavelength. A comparator produces an error signal when the output signal differs from zero. A gain control automatically controls the signal level of the detection signal to reduce the output signal substantially to zero with the nonabsorbent gas filling the sample cell. The preselected conditions may include the passage of a predetermined time and a temperature drift beyond a predetermined limit.

Growing community of inventors

Oakland, CA, United States of America

Raymond E Rogers