JP3175290B2 - Oxygen concentration detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen concentration detecting apparatus using a galvanic cell type oxygen sensor or the like whose sensor output decreases due to aging.

[0002]

2. Description of the Related Art In an oxygen concentration detecting device provided with a galvanic cell type oxygen sensor, there is a problem that the output of the galvanic cell type oxygen sensor is reduced by aging. Accordingly, the applicant of the present application has taken measures to reduce the sensor output,
The sensor output measured at predetermined intervals is set as a reference output corresponding to the standard oxygen concentration in the atmosphere (20.6%). In the subsequent measurement, the measured output is compared with the reference output to determine the oxygen concentration. Was previously proposed (Japanese Patent Application No. 3-202887).

[0003]

However, setting the above-mentioned predetermined fixed period, that is, the reference output update period to be constant, is that the rate of aging of the galvanic cell type oxygen sensor immediately after the start of use is short. It is not rational to pay attention to the fact that it is low and becomes high as the service life approaches. That is, immediately after the start of use, unnecessary renewal is frequently performed, and when the life is approaching, renewal is not performed sufficiently, and the measured oxygen concentration becomes lower than the actual one. The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an oxygen concentration detection device in which the reference output of the oxygen sensor corresponding to the standard oxygen concentration is updated at an appropriate time.

[0004]

According to the present invention, in order to achieve the above object, an update interval for updating the reference output of the oxygen sensor with respect to the standard oxygen concentration is changed according to the measured oxygen concentration.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. FIG. 1 is a diagram illustrating a circuit configuration of the oxygen concentration detection device according to the present embodiment. In the figure, a reference clock signal generated by an oscillation circuit 1 is divided by a frequency dividing circuit 2 to a predetermined frequency and output to a time counting circuit 3. The time counting circuit 3 counts the time signal from the frequency dividing circuit 2 and obtains time data.
Output to PU5. The date counting circuit 4 includes the time counting circuit 3
The day carry signal is counted to obtain date data, and the date data is output to the CPU 5 together with the week carry signal and the month carry signal.

The oxygen sensor 6 is composed of, for example, a galvanic cell type oxygen sensor and outputs a voltage proportional to the oxygen concentration in the air. After the output voltage of the oxygen sensor 6 is amplified by the amplifier circuit 7, the output voltage is converted into an 8-bit digital value of 0 to 255 by the A / D converter circuit 8 and output to the CPU 5. The amplification circuit 7 and the A / D conversion circuit 8 are driven by measurement signals output from the CPU 5 at one-minute intervals.

The CPU 5 is a central processing unit for controlling the entire circuit. The CPU 5 stores the oxygen concentration data and the like detected by the oxygen sensor 6 in the RAM 9 and drives the display drive circuit 10 to display the time and date data. It is displayed on the unit 11.

The display section 11 is composed of a liquid crystal display or the like.
The upper part is provided with ten oxygen concentration indicators 11a to 11j indicating the level relating to the oxygen concentration. These oxygen concentration indicators are placed in an environment of the standard oxygen concentration when the oxygen concentration detecting device is placed in the environment of the standard oxygen concentration. Are turned on when the reference output is the reference output, and as the output of the oxygen sensor 6 decreases, the number of lights decreases according to the degree. A segment display is provided at the center and lower part of the display unit 11 to display the date and time.

The key processing section 12 is composed of a plurality of keys operated at the time of time correction, at the start of measurement of oxygen concentration, and the like, and operation signals of these keys are output to the CPU 5. FIG.
FIG. 4 is a diagram showing a configuration of a register of a RAM 9. The RAM 9 stores a value from an A / D conversion circuit 8 corresponding to an output detected by an oxygen sensor 6, that is, a measured oxygen concentration storage unit X that stores measured oxygen concentration data. At regular intervals (for example, every month or week), an average of the measured oxygen concentration data measured at that time and the reference oxygen concentration data set up to that time is set as new reference oxygen concentration data. An oxygen concentration storage unit Y, a level storage unit Z for storing level data which is a value obtained by subtracting a measured oxygen concentration data value from a reference oxygen concentration data value, and an aging of the oxygen sensor 6 are advanced, and outputs thereof are predetermined. And an aging flag FK that is set to 1 when the value falls below a certain value.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. First, it is determined in step S1 whether minute carry has occurred. If the minute carry has occurred, it is the timing for measuring the oxygen concentration every minute, so in the next step S2, the amplifier circuit 7 and the A / D conversion circuit 8 are driven to measure the oxygen concentration, and the measurement data is measured. It is stored in the oxygen concentration storage unit X. Further, in step S3,
The current measured oxygen concentration data value is subtracted from the reference oxygen concentration data value set in the reference oxygen concentration storage unit Y, and the result, that is, level data is obtained.
Set to.

Next, in step S4, it is determined whether the measured oxygen concentration data value set in the measured oxygen concentration storage unit X is larger than the reference oxygen concentration data value set in the reference oxygen concentration storage unit Y. If it is larger, the current measured oxygen concentration data is set as the reference oxygen concentration data in the reference oxygen concentration storage unit Y in step S5, and then the process proceeds to step S6. If it is determined that it has not become larger, the process proceeds directly to step S6. In step S6, the aging flag of the oxygen sensor 6 is small.
Is determined to be 0, and the aging flag FK
If the value is 0, the process proceeds to step S7, where it is determined whether or not a month carry signal has been sent. If so, the process proceeds to step S9. If it is determined in step S6 that the value of the aging flag FK is 1 instead of 0, the flow advances to step S8 to determine whether a weekly carry signal has been sent. If it has, the flow advances to step S9. move on. In step S9, the measured oxygen concentration data value in the measured oxygen concentration storage unit X and the reference oxygen concentration data value in the reference oxygen concentration storage unit Y are added, and the sum is divided by 2 to obtain an average value of the two. It is set in the reference oxygen concentration storage unit Y as new reference oxygen concentration data. That is, the reference oxygen concentration data in the reference oxygen concentration storage unit Y is updated every month when the oxygen sensor 6 is approaching the end of its life, and every week when the oxygen sensor 6 is approaching its end of its life. Will go on.

After the process of step S9 is completed, the process proceeds to step S10, where it is checked whether the reference oxygen concentration data in the reference oxygen concentration storage unit Y has become less than a predetermined value α, and the value is determined to be less than the value α. If it has decreased to a value lower than the value α, the process proceeds to step S11 to set 1 to the aging flag FK.
From 0, the process proceeds to step S12, and the value of the aging flag FK is set to 0. After finishing the processing in step S11 or S12, or when making a negative determination in step S7 or S8, the process proceeds to step S13, and the display unit 11
Display processing for displaying each data. That is,
First, the level data of the level storage unit Z is displayed by the ten oxygen concentration display units 11a to 11j. In this case, as shown in FIG.
When the level data value of is up to 1, the oxygen concentration indicator 1
All of 1a to 11j are turned on, and thereafter, as the oxygen concentration decreases and the level data value of the level storage unit Z increases, the number of lights to be turned off increases (that is, the number of lights to be turned on decreases). Value is 29 or more and 33
When the level data value reaches 34, all the lights are turned off. When the level data value becomes 34 or more, the oxygen concentration indicator 11a is turned off.
To 11j are blinkingly displayed. After the display of the level data, the date data from the date counting circuit 4 and the current time data from the time counting circuit 3 are displayed on the center and lower segment display bodies of the display unit 11, respectively. For example, when it is currently 8:35:20 on Monday, January 23, and the level data value of the level storage unit Z is a value up to 1, the display unit 1
The display of 1 is as shown in FIG. 5 (a) with all of the oxygen concentration indicators 11a to 11j turned on, and the elapsed time from the above time is 11:40:15. When the level data value is also in the range of 8 to 9, the display on the display unit 11 shows four oxygen concentration indicators 11a.
11d are turned off, and the state becomes as shown in FIG.

After the display processing in step S13 is completed, the process returns to step S1. If it is determined in step S1 that no minute carry has been sent, the flow advances to step S15 to determine whether a key input has been performed. If a key input has been performed, the flow advances to step S15 to execute a key process corresponding to the key input. After the execution, the process proceeds to the display process of step S13, but if there is no key input, the process directly proceeds from step S15 to the display process of step S13.

The present invention is not limited to the above embodiment, but can be variously modified and applied without departing from the present invention. For example, in the present embodiment, the update period of the reference oxygen concentration data is set to 1 based on whether the reference oxygen concentration data in the reference oxygen concentration storage unit Y has become less than a predetermined value α.
Although the switching is performed from one month to one week, such switching may be performed a plurality of times, and the update period may be further set in accordance with the degree of deterioration of the oxygen sensor 6. Oxygen sensor 6 which is finely performed in stages
It goes without saying that the update period may be changed (shortened) in conjunction with the degree of deterioration.

[0015]

As described in detail above, the present invention relates to an oxygen concentration detecting apparatus which changes an update interval for updating a reference output of an oxygen sensor with respect to a standard oxygen concentration in accordance with measured oxygen concentration data. Therefore, it is possible to provide an oxygen concentration detecting device in which the updating is performed at an appropriate time without any excess or shortage.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of one embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a RAM in FIG. 1;

FIG. 3 is a flowchart showing the operation of the embodiment.

FIG. 4 is a diagram showing a relationship between a lighting mode of an oxygen concentration display of FIG. 1 and level data relating to oxygen concentration.

FIG. 5 is a diagram showing an example of a display mode of a display unit.

[Explanation of symbols]

 3 Time counting circuit 4 Date counting circuit 6 Oxygen sensor 8 A / D conversion circuit 9 RAM 11 Display section 11a to 11j Oxygen concentration display X Measurement oxygen concentration storage section Y Reference oxygen concentration storage section Z Level storage section FK Aging flag

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01N 27/12 G01N 27/26 371 G01N 27/404 G01N 27/00

Claims (1)

(57) [Claims] 1. An oxygen sensor, a measured oxygen concentration data generating means for obtaining measured oxygen concentration data from an output of the oxygen sensor, a reference oxygen concentration data storage means for storing reference oxygen concentration data, and a reference oxygen concentration data storage Means for obtaining an oxygen concentration level from the reference oxygen concentration data of the means and the measured oxygen concentration data; and storing the reference oxygen concentration data based on the measured oxygen concentration data obtained by the measured oxygen concentration data generating means at predetermined intervals. An oxygen concentration detecting device comprising: updating means for updating reference oxygen concentration data of the means; and changing means for changing an update interval of the reference oxygen concentration data in accordance with the measured oxygen concentration data.