Gas analyzer and method of calibrating said gas analyzer

• US 5,780,710 A
• Filed: 05/27/1997
• Issued: 07/14/1998
• Est. Priority Date: 05/30/1996
• Status: Expired due to Term

• Current Assignee: NGK Insulators Limited
• Original Assignee: NGK Insulators Limited
• Inventors: Usami, Jun, Murase, Takao, Kon, Masao
• Primary Examiner(s): RAEVIS, ROBERT R
• Application Number:
  US08/863,617
• Time in Patent Office: 413 Days
• Field of Search: 73/1.06, 73/1.07, 73/23.31, 204/426, 204/427, 205/781, 205/784, 422/94, 422/98
• US Class Current: 73/1.06
• CPC Class Codes: G01N 27/4175 Calibrating or checking the analyser
• CPC Class Codes: G01N 27/419 Measuring voltages or currents with a combination of oxygen pumping cells and oxygen concentration cells

Abstract

A gas analyzer includes a gas sensor, a drive section that pumps oxygen in first to third processing zones of the gas sensor, an operating section that operates a pumping current flowing in a third electro-chemical pump cell into a gas value to be measured, a display output section that displays a value operated by the operating section, or outputs the value as an electrical output to the external, and a heater drive section that heats the gas sensor to a predetermined temperature.

Claims

1. A gas analyzer comprising:

a gas sensor in which after a gas to be measured containing a gas component to be measured having bound oxygen to be measured is introduced into a first processing zone under a predetermined diffusion resistance, and an oxygen partial pressure in the atmosphere within said first processing zone is controlled to a predetermined oxygen partial pressure due to the pumping action of oxygen by the first electro-chemical pump cell in said first processing zone, the gas to be measured is introduced into a second processing zone under a predetermined diffusion resistance, and oxygen is pumped out by the second electro-chemical pump cell in the second processing zone, so that the oxygen partial pressure in said atmosphere is controlled to a low oxygen partial pressure value that does not substantially influence the measurement of the amount of the gas component to be measured, and thereafter the gas to be measured is introduced into a third processing zone, and said gas component to be measured in the atmosphere introduced from said second processing zone is reduced or decomposed in said third processing zone, and oxygen generated at that time is pumped out by a third electro-chemical pump cell to detect a pumping current flowing in said third electro-chemical pump cell;

a drive section for pumping oxygen from said first to third processing zones in said gas sensor;

an operating section for operating the pumping current flowing in said third electro-chemical pump cell into a value of the gas to be measured;

a display output section for displaying the value operated by said operating section, or outputting the value to an external as an electric output; and

a heater drive section for heating said gas sensor to a predetermined temperature.

2. A gas analyzer as claimed in claim 1, wherein the gas component to be measured is NO_x.

3. A gas analyzer as claimed in claim 2, wherein the pumping current in the first processing zone and the pumping current in the second processing zone are introduced into said operating section, and said operating section operates the pumping currents in the first and second processing zones to output the amount of oxygen, the amount of insufficient oxygen or its equivalent in the atmosphere to be measured.

4. A gas analyzer as claimed in claim 3, wherein the measured NO_x is corrected according to the amount value of oxygen, the amount value of insufficient oxygen or an equivalent value of oxygen in the atmosphere to be measured.

5. A gas analyzer as claimed in claim 1, wherein the pumping current in the first processing zone and the pumping current in the second processing zone are introduced into said operating section, and said operating section operates the pumping currents in the first and second processing zones to output the amount of oxygen, the amount of insufficient oxygen or its equivalent in the atmosphere to be measured.

6. A gas analyzer as claimed in claim 1, wherein at least said drive section is integrated with said gas sensor.

7. A method of calibrating a gas analyzer which includes a gas sensor in which after a gas to be measured containing a gas component to be measured having bound oxygen to be measured is introduced into a first processing zone under a predetermined diffusion resistance, and an oxygen partial pressure in the atmosphere within said first processing zone is controlled to a predetermined oxygen partial pressure due to the pumping action of oxygen by the first electro-chemical pump cell in said first processing zone, the gas to be measured is introduced into a second processing zone under a predetermined diffusion resistance, and oxygen is pumped out by the second electro-chemical pump cell in the second processing zone, so that the oxygen partial pressure in said atmosphere is controlled to a low oxygen partial pressure value that does not substantially influence the measurement of the amount of the gas component to be measured, and thereafter the gas to be measured is introduced into a third processing zone, and said gas component to be measured in the atmosphere introduced from said second processing zone is reduced or decomposed in said third processing zone, and oxygen generated at that time is pumped out by a third electro-chemical pump cell to detect a pumping current flowing in said third electro-chemical pump cell;

said method comprising the step of;

calibrating said gas analyzer with a plurality of known gas component to be measured as a standard gas and a pumping current corresponding to the standard gas as a calibration curve.

8. A method of calibrating a gas analyzer as claimed in claim 7, wherein a standard gas containing at least H₂ O and CO₂ is used as the known gas component to be measured other than the gas component to be measured.

9. A method of calibrating a gas analyzer as claimed in claim 8, wherein a temperature of said gas sensor is increased 50°

C. higher than a working temperature for a predetermined time before measuring the calibration curve, and the temperature of said gas sensor is returned to the working temperature to prepare the calibration curve of the standard gas.

10. A method of calibrating a gas analyzer as claimed in claim 7, wherein a temperature of said gas sensor is increased 50°

C. higher than a working temperature for a predetermined time before measuring the calibration curve, and the temperature of said gas sensor is returned to the working temperature to prepare the calibration curve of the standard gas.

11. A method of calibrating a gas analyzer as claimed in claim 7, wherein, before measuring the calibration curve, said gas sensor is separated from said drive section, and an alternating current power supply is connected between respective electrode pairs of said first to third processing zones, and after an alternating current of 1 Hz or higher is supplied for a predetermined time, said gas sensor is returned to a drive state to prepare the calibration curve of the standard gas.