AUTOMATIC CALIBRATION CIRCUIT FOR GAS ANALYZERS

• US 3,812,330 A
• Filed: 08/18/1972
• Issued: 05/21/1974
• Est. Priority Date: 08/18/1972
• Status: Expired due to Term

• Current Assignee: Daniel I. Schneiderman, Lloyd D. Bowman, Manohar G. Karhade
• Original Assignee: Daniel I. Schneiderman, Lloyd D. Bowman, Manohar G. Karhade
• Inventors: Bowman, Lloyd D., Karhade, Manohar G., Schneiderman, Daniel I.
• Primary Examiner(s): Henon, Paul J.
• Assistant Examiner(s): Gnuse, Robert F.
• Application Number:
  US05/281,819
• Time in Patent Office: 641 Days
• Field of Search: 235/92EV,92FQ,92PE,92CC 324/78D,79D
• US Class Current: 377/50
• CPC Class Codes: G06M 3/00 Counters with additional facilities generating electric pulses at random intervals H03K3/84
• CPC Class Codes: G06M 3/02 for performing an operation at a predetermined value of the count, e.g. arresting a machine G06M3/04 takes precedence

Abstract

A circuit for automatically correcting the electronic calibration count in a system for measuring the concentration of a radiation absorbing agent in a gas mixture. The ideal calibration count is a digital number which is proportional to a detector signal determined by the Beer-Lambert Law.

Claims

1. An automatic calibration circuit for apparatus used for measuring the concentration of a radiation absorbing agent in a gas mixture, comprising:

a sample counter capable of counting in forward and reverse directions;

a reference counter capable of counting in forward and reverse directions;

first means for activating said sample counter and said reference counter in the forward direction iN response to a first digital signal representative of the quantity of radiation passed through the gas mixture without the radiation absorbing agent;

means for comparing the count in said sample counter with a preset calibration count;

first means for disabling said reference counter and said sample counter when the count in said sample detector is equal to the preset calibration count;

second means for activating said sample counter and said reference counter in the reverse direction in response to a second digital signal representative of the quantity of radiation passed through the gas mixture with the radiation absorbing agent; and

second means for disabling said reference counter and said sample counter when the count in said reference counter is at a predetermined value.

2. An automatic calibration circuit for apparatus used for measuring the concentration of a radiation absorbing agent in a gas mixture utilizing a first digital signal representative of the quantity of radiation passed through the gas mixture without the radiation absorbing agent and a second digital signal representative of the quantity of radiation passed through the gas mixture with the radiation absorbing agent, the automatic calibration circuit comprising:

a sample counter capable of counting in forward and reverse directions;

a reference counter capable of counting in forward and reverse directions;

first means for activating said sample counter and said reference counter in the forward direction in response to the first digital signal;

means for comparing the count in said sample counter with a preset calibration count;

first means for disabling said reference counter and said sample counter when the count in said sample counter is equal to the preset calibration count;

second means for activating said sample counter and said reference counter in the reverse direction in response to the second digital signal; and

second means for disabling said reference counter and said sample counter when the count in said reference counter is zero.

3. An automatic calibration circuit used for appatatus measuring the concentration of a radiation absorbing agent in a gas mixture including a first digital signal representative of the quantity of radiation passed through the gas mixture without the radiation absorbing agent and a second digital signal representative of the quantity of radiation passed through the gas mixture with the radiation absorbing agent, the calibration circuit comprising:

a sample reversible counter and a reference reversible counter;

first means for activating said sample reversible counter and said reference reversible counter in a first direction in response to the first digital signal;

means for comparing the count in said sample reversible counter with a preset calibration count;

first means for disabling said reference reversible counter and said sample reversible counter when the count in said sample reversible counter is equal to the preset calibration count;

second means for activating said sample reversible counter and said reference reversible counter in a second direction in response to the second digital signal; and

second means for disabling said reference reversible counter and said sample reversible counter when the count in said reference reversible counter is zero.

4. The automatic calibration circuit is in claim 3 wherein the first direction is a forward direction and the second direction is a reverse direction.

5. An automatic calibration circuit used for apparatus measuring the concentration of a radiation absorbing agent in a gas mixture including a reference digital electrometer for producing a first digital signal representative of the quantity of radiation passed through the gas mixture without the radiation absorbing agent and a sample digital electrometer for producing a second digital signal representative of the quantity of radiation passed through thE gas mixture with the radiation absorbing agent, the automatic calibration circuit comprising:

a sample reversible counter capble of counting in forward and reverse directions;

a reference reversible counter capble of counting in forward and reverse directions;

first means for activating said sample reversible counter and said reference reversible counter in the forward direction in response to the first digital signal;

means for comparing the count in said sample reversible counter with a preset calibration count;

first means for disabling said reference reversible counter and said sample reversible counter when the count in said sample reversible counter is equal to the preset calibration count;

second means for activating said sample reversible counter and said reference reversible counter in the reverse direction in response to the second digital signals; and

second means for disabling said reference reversible counter and said sample reversible counter when the count in said reference reversible counter is zero.

6. An automatic calibration circuit used for apparatus measuring the concentration of the radiation absorbing agent in a gas mixture, comprising:

means for producing a first digital signal representative of the quantity of radiation passed through the gas mixture without the radiation absorbing agent;

second means for producing a second digital signal representative of the quantity of radiation passed through the gas mixture with the radiation absorbing agent;

a sample reversible counter capable of counting in forward and reverse directions;

a reference reversible counter capable of counting in forward and reverse directions;

first means for activating said sample reversible counter and said reference reversible counter in the forward direction in response to the first digital signal;

means for comparing the count in said sample reversible counter with a preset calibration count;

first means for disabling said reference reversible counter and said sample reversible counter when the count in said sample reversible counter is equal to the preset calibration count;

second means for activating said sample reversible counter and said reference reversible counter in the reverse direction in response to the second digital signals;

second means for disabling said reference reversible counter and said sample reversible counter when the count in said reference reversible counter is zero; and

means for comparing the count of the sample counter with the increased calibration count.

7. The automatic calibration circuit as in claim 6 wherein the radiation absorbing agent is ozone and including a radiation source emitting light waves in the ultraviolet range.

8. The automatic calibration circuit as in claim 7 wherein said radiation source is a Mercury vapor source.

9. An apparatus used for measuring the concentration of a radiation absorbing agent in a gas mixture, comprising:

a first means for receiving a first gas mixture with the radiation absorbing agent in the gas mixture;

a second means for receiving a second gas mixture without the radiation absorbing agent;

a sample forming an absorption chamber, said sample cell having a radiation entry pathway and a radiation exit pathway;

a valve means having a first and a second position connecting said first means to said sample cell in a first position and connecting said second means to said sample cell in a second position;

a radiation source having a first area, said first area position for directing radiation through said radiation entry pathway of said sample cell thereby passing through said first gas mixture when said valve means is in the first position, and through said second gas mixture when said valve means is in the second position;

a first detector means for receiving radiation from said first area of said radiation source;

a second detector means for receiving rAdiation from said first area of said radiation source after the radiation has passed through the gas mixture of said sample cell at the radiation exit pathway of said sample cell;

a first measuring means for measuring the quantity of radiation received by said first detector means;

a second measuring means for measuring the quantity of radiation received by said second detector means; and

a comparator means coupled with said first and second measuring means for determining the difference in radiation absorption between the first gas mixture and the second gas mixture;

wherein the improvement comprises;

a sample reversible counter capable of counting in forward and reverse directions;

a reference reversible counter capable of counting in forward and reverse directions;

first means for activating said sample reversible counter and said reference reversible counter in the forward direction in response to a first digital signal representative of the quantity of radiation passed through the second gas mixture;

means for comparing the count in said sample reversible counter with a preset calibration count;

first means for disabling said reference reversible counter and said sample reversible counter when the count in said sample reversible counter is equal to the preset calibration count;

second means for activating said sample reversible counter and said reference reversible counter in the reverse direction in response to a second digital signal representative of the quantity of radiation passed through the first gas mixture; and

second means for disabling said reference reversible counter and said sample reversible counter when the count in said reference reversible counter is zero.

10. An automatic calibration circuit used for apparatus measuring the concentration of a radiation absorbing agent in a gas mixture, comprising;

receiving means for receiving a first gas mixture with the radiation absorbing agent;

a sample cell forming an absorption chamber, said sample cell having a radiation entry pathway and a radiation exit pathway;

valve means having a first and a second position connected to said sample cell;

a first passageway from said receiving means to said valve means, said valve being in the first position when passing the first gas mixtures through said first passageway to said first sample cell;

a second passageway, including a filter for removing the radiation absorbing agent from the first gas mixture thereby forming a second gas mixture, from said receiving means to said valve means, said valve means being in the second position when passing the second gas mixture through said second passageway to said sample cell;

a radiation source, having a first area, said first area positioned for directing radiation through said radiation entry pathway of said sample cell and through said radiation exit pathway of said sample cell thereby passing through said first gas mixture when said valve means is in said first position and through said second gas mixture when said valve means is in said second position;

first detector means for receiving radiation from said first area of said radiation source;

second detector means for receiving radiation from said first area of said radiation source after the radiation had passed through the gas mixture into the sample cell at the radiation exit pathway of said sample cell;

first measuring means for measuring a quantity of radiation received by said first detection means;

second measuring means for measuring the quantity of radiation received by said second detector means;

a sample reversible counter connected to said second measuring means;

a reference reversible counter connected to said first measuring means;

first means for activating said sample reversible counter and said reference reversible counter in the forward direction in response to a first digital signal representative of the quantity of radiatioN passed through the gas mixture without the radiation absorbing agent;

means for comparing the count in said sample reversible counter with a preset calibration count;

first means for disabling said reference reversible counter and said sample reversible counter when the count in said sample reversible counter is equal to the preset calibration count;

secon means for activating said sample reversible counter and said reference reversible counter in the reverse direction in response to a second digital signal representative of the quantity of radiation passed through the gas mixture including the radiation absorbing agent;

second means for disabling said reference reversible counter and said sample reversible counter when the count in said reference reversible counter is zero; and

means for displaying a representation of the count remaining in said sample reversible counter after said sample reversible counter has been activated in the forward and reverse direction.