US 4,847,783 A · Gas sensing instrument

Abstract

A gas sensing instrument provides programmable control of the operating temperatures of an array of gas sensors for the detection of target gases in air. The control facilitates precise temperature setpoint resolution. The gas sensors in the array have an improved construction density with reduction in size and an extended operating life provided by reduced power consumption. A programmable circuit functions as a programmable-resistor temperature controller in a Wheatstone bridge configuration. A multiplying digital to analog converter circuit controls the ratio of voltage to current that functions as a resistance equivalent. The programmable circuit is interfaced with a computer to provide selectable temperature control for at least 256 setpoints.

Claims20

Dependent claims

An instrument for simultaneously quantifying the concentrations of a number of gases present in an oxygen containing atmosphere comprising,

a computer for providing a quantitative presentation of the gas concentrations,
a number of semiconductor gas sensing elements at least equal in number to the number of gases to be detected,
said gas sensing elements each having a predetermined quantifiable response characteristic differing from the response characteristic of the other of said gas sensing elements in response to at least one of the gases to be detected,
temperature control means for maintaining the temperature of each gas sensing element at a selected value by compensating for thermal variations in the surrounding environment,
said temperature control means coupled to and responsive to said computer to maintain each of said gas sensing elements at a selected one of a number of operating temperatures,
measurement means connected to each of said gas sensing elements for generating an electrical signal representing the response of each of said respective gas sensing elements to each of the gases to be detected,
said measurement means electrically connected to said computer, and
said computer including means for converting said electrical signals from said measurement means to a digital representation,

5 more elements

A system for simultaneous detection of the quantifiable concentration of a number of target gases in an oxygen containing atmosphere comprising,

a number of gas sensors at least equal in number to the number of gases to be detected, each of said gas sensors including a layer of gas sensing material,
means for supporting each layer of gas sensing material,
a pair of metallic electrodes in contact with each layer of gas sensing material,
means for supplying a voltage to said electrodes to apply a voltage to said gas sensing material,
a resistance measuring device connected to said electrodes,
said resistance measuring device converting the values of the electrical resistances of said electrodes to a plurality of digital output signals,
signal processing means for receiving said digital output signals from said resistance measuring device,
means for transmitting the value of said electrical resistances in the form of said digital output signals to said signal processing means, and
said signal processing means converting said digital output signals to a quantifiable value of the concentrations of the target gases detected.

6 more elements

A gas detecting instrument comprising,

a number of electrically insulating substrates,
at least a single pair of electrodes positioned on each of said substrates,
a layer of gas sensing material in contact with said electrodes on each of said substrates,
a voltage source connected to said electrodes,
means for controlling the temperature of each of said gas sensing materials at preselected values,
means for measuring the electrical resistance of said gas sensing material in response to a number of gases to be detected in air at least equal in number to the number of said single pair of electrodes,
an analog to digital converter connected to said means for measuring the electrical resistance for converting the value of the measured electrical resistance to a digital representation, and
a signal processor connected to said analog to digital converter for receiving the measurement of the electrical resistance in said digital representations and computing a quantifiable value of the gas concentrations detected from the electrical resistance measurements.

5 more elements

Dependencies are inferred from the claim text.

Gas sensing instrument

Life of this patent

Gas sensing instrument

Life of this patent

Abstract

Claims20