JPH01222769A - Calibration of gas sensor in incubator - Google Patents

Abstract

PURPOSE:To facilitate the calibration of a gas sensor, by feeding a prescribed amount of gas into the vessel, calculating the standard value in the vessel on the basis of the gas feed and the capacity of the vessel, and calibrating the measuring value of the sensor on the basis of the standard value. CONSTITUTION:The volume of the gas such as carbon dioxide gas to be fed into the vessel 2 is adjusted on the basis of the value detected by the gas sensor 16 in the vessel 2. At this time, a prescribed amount of the gas is fed into the vessel and the standard value is calculated from the gas feed and the capacity of the vessel and the measured value of the gas sensor is calibrated on the basis of the standard value. Resultingly, the calibration of the sensor can be done without another device for measuring the concentration.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for calibrating a gas sensor in an incubator used for tissue/cell culture, etc.

(Conventional technology and its problems) A conventional incubator has a gas sensor for measuring concentration installed inside the storage chamber, a solenoid valve that adjusts the supply of gas into the storage chamber, and a measured concentration value detected by the gas sensor. and a control unit that controls the opening and closing of the electromagnetic valve so that the gas concentration in the storage reaches a predetermined concentration value based on the following.

Generally, in such incubators, the output voltage level of the gas sensor changes under the same environmental conditions due to aging of the gas sensor, and the measured concentration value detected by the gas sensor differs from the actual gas concentration value inside the chamber. becomes. For this reason, it is necessary to calibrate the gas sensor about once every six months.

Gas sensors in conventional incubators are calibrated by comparing the output characteristics of the gas sensor installed in the incubator with the output characteristics of a separately prepared accurate concentration measuring device (gas sensor). however,
Such a calibration method has a problem in that the calibration work is complicated, such as preparing a separate concentration measuring device.

(Objective of the Invention) An object of the present invention is to provide a method for calibrating a gas sensor in an incubator, which solves the problems of the above-mentioned prior art and allows the calibration of a gas sensor to be easily performed without separately preparing a concentration measuring device. .

(Means for Achieving the Object) The present invention provides a method for calibrating a gas sensor in an incubator, which adjusts the amount of gas supplied into the storage chamber based on a measured concentration value detected by a gas sensor inside the storage chamber. In order to achieve the above object, a predetermined amount of gas is supplied into the storage chamber, and a reference concentration value inside the storage chamber is calculated based on the supply amount of the gas and the volume inside the storage chamber,
The concentration value measured by the gas sensor is corrected based on the reference concentration value.

(Example) FIG. 1 is a cross-sectional view showing an incubator used to carry out a gas sensor calibration method according to an example of the present invention. As shown in the figure, a housing 2 is formed in a substantially box-shaped main body 1, and within the housing 2, a plurality of shelves 3 are arranged horizontally at equal intervals in the vertical direction. will be established. Further, an opening 4 is formed on the front side of the main body 1, and an inner door 5 and an outer door 6 are respectively attached so as to be openable and closable so as to close the opening 4. A door heater 7 is attached to the inner surface of the outer door 6, and is configured so that when the temperature of the inner W15 decreases due to opening/closing operations of the doors 5, 6, etc., the door heater 7 generates heat to prevent the temperature inside the refrigerator from decreasing. There is. In addition, a water jacket 8 is provided in the main body 1 so as to wrap around the housing 2 while avoiding the area of the opening 4, and a heater 9 is attached to the lower end of the water jacket 8, so that the heater 9 generates heat. , the water in the water jacket 9 is heated to raise the temperature inside the refrigerator.

In addition, a gas pipe 10 is disposed through the back plate of the main body 1 and the water jacket 8 so that one end faces into the storage compartment 2.
The main body 1 is connected to a gas cylinder such as a CO2 gas cylinder (not shown) via a solenoid valve 11 and a pressure regulator 12 for adjusting gas pressure on the outside of the main body 1. By opening and closing the solenoid valve 11, gas is supplied to the storage chamber 2. It is configured to be supplied and stopped.

Further, an R temperature sensor 13 is attached to the inner surface of the outer R6, and the rR temperature sensor 13 and the door heater 7 are connected to the control section 14. Based on the output signal from the temperature sensor 51, the control section 14 The door heater 7 is made to generate heat in a timely manner by lj! It is configured so that the temperature around 5.6 is maintained at a predetermined value. Furthermore, water jacket 8
A temperature sensor 15 is installed inside the temperature sensor 15.
and the heater 9 are also connected to the control unit 14, and the control unit 14 causes the heater 9 to generate heat in a timely manner based on the output signal from the temperature sensor 15 to adjust the water temperature in the water jacket 7, thereby controlling the temperature inside the refrigerator. It is configured to be controlled to a predetermined value. Furthermore, a gas sensor 1 is installed inside the storage 2.
6 is installed, and its gas sensor 16 and solenoid valve 11 are also connected to the control unit 14, and the control unit 14 determines the measured gas concentration value (hereinafter referred to as (details will be described later), and controls the opening and closing of the solenoid valve 11 so that the measured concentration value becomes equal to the gas concentration value set by the operator (hereinafter referred to as the set concentration value). It is composed of

FIG. 2 is a graph showing an example of the relationship between the concentration and output voltage at each internal temperature of the gas sensor 16. As is clear from this graph, when the output voltage (mV) of the gas sensor 16 and the temperature inside the refrigerator ('C) are known, the CO2 gas concentration (V) inside the refrigerator can be determined.

1%). In this incubator, focusing on the above point, data that corresponds the internal temperature measured by the temperature sensor 15, the output voltage of the gas sensor 16, and the measured concentration value is stored in advance in the memory of the control unit 14 as a table. There is.

When the incubator is operating, the gas sensor 16
The measured concentration value is obtained from time to time using the above table based on the output voltage from the refrigerator and the temperature inside the refrigerator measured by the temperature sensor 15, and the solenoid valve 11 is opened and closed so that the gas concentration inside the refrigerator reaches the set concentration value. Control.

In such an incubator, if the output voltage level of the gas sensor 16 changes due to aging, the measured concentration value read from the table will also differ from the actual concentration value in the chamber, reducing control accuracy. Therefore, it is necessary to calibrate the gas sensor 16, and in this embodiment, the calibration is performed as follows. However, prior to the actual calibration work, the gas sensor 16
Considering that the output voltage level changes due to aging and deterioration of the gas sensor, a table showing the relationship between the internal temperature, the output voltage of the gas sensor 16, and the measured concentration value is created based on the voltage level of the gas sensor 16. A plurality of them are created corresponding to the change stage and stored in the memory of the control unit 14 in advance.

In the calibration work, first, the reference concentration value in the accommodation Ji[2 is determined as follows. That is, the inner door 5 and the outer door 17i!
6 is opened to bring the inside of the housing J*2 into an atmospheric condition, and then the inner door 5 and the outer door 1ti6 are closed. Next, the solenoid valve 11 is opened to supply gas into the refrigerator, and at a predetermined time 2t (M) has elapsed, the solenoid valve 11 is opened to stop the gas supply. Now, when the gas flow rate set by the pressure regulator during gas supply is Ql/M), the gas supply amount is V(), and the volume V in the accommodation j12 is (1), the gas supply time t (M) and the gas Ideally, a proportional relationship as shown by the broken line in FIG. 3 is established.

Under this condition, the gas supply to the chamber is jlv (1)
is expressed as V=Q-t (1), therefore, the reference concentration value c(
vat%) is c - (v/V) X 100
It can be calculated by =-(2). However, in reality, the proportional relationship shown by the broken line in Figure 3 does not hold.
For example, a nonlinear relationship as shown by the solid line in FIG. 3 is established. However, in FIG. 3, the volume V of accommodation jI2 is 1
60 (1) and the case where the gas flow ff1Q is 1 (I/M) (7) is shown. Even considering that there is a gas leak from 111111 of inner Wi5 and main body 1, gas supply 1v (1)
In other words, as the gas supply time t(M) increases, the internal pressure of the storage chamber j[2 increases.However, since the supplied gas is set at a constant pressure, the internal pressure of the storage chamber 2 and the pressure of the supplied gas The gas flow ff1Q(j!/
This is because M) decreases. Therefore, for example, the gas supply MV (j and gas supply time t) as shown by the solid line in FIG.
(M) is experimentally determined in advance, and based on this experimental result, the gas supply amount Vl) is determined from the gas supply time t (M), and this is substituted into the above equation (2) to determine the reference value. Calculate the concentration value C.

While calculating the reference concentration value C as described above, 1, the output voltage level of the gas sensor 16 at that time and the temperature inside the refrigerator are measured by the temperature sensor 15.

Assuming that the output voltage level of the gas sensor 16 is changing due to aging, the measured concentration value specified by the table based on the output voltage level and the temperature inside the refrigerator is different from the reference concentration C. It becomes. Therefore, a table is created in which a measured concentration value equal to the reference concentration value C is specified based on the output voltage level of the gas sensor 16 and the temperature inside the refrigerator. A program stored in the memory of the control unit 14 is rewritten so that the table is selected from among the tables and the table is selected during normal operation of the incubator.

As described above, according to the gas sensor calibration method in this incubator, the reference concentration value C is calculated based on the gas supply interval and the volume of the storage chamber 2, and the measured concentration value of the gas sensor 16 is corrected based on the reference concentration value C. Therefore, there is no need to prepare a separate concentration measuring device, and calibration work can be easily performed.

In the above embodiment, a case was explained in which the correction is made by changing the program of the control unit 14, but the output voltage of the gas sensor 16 may be changed and adjusted using a variable resistor or the like without changing the program to calibrate the gas sensor. You may also do so.

(Effects of the Invention) As described above, according to the method for calibrating a gas sensor in an incubator of the present invention, a reference concentration value is calculated from the gas supply amount and the volume of the storage chamber, and the measured concentration of the gas sensor is calculated based on the reference concentration value. Since the gas sensor is calibrated by correcting the value, there is no need to prepare a separate concentration measuring device (the calibration work can be easily performed).

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an incubator to which an embodiment of the present invention is applied, FIG. 2 is a graph showing the relationship between gas concentration and output voltage at each internal temperature of the gas sensor, and FIG. 3 is a graph showing the relationship between the gas supply amount and the gas supply time within the range.

Claims (1)

[Claims] (1) In an incubator that adjusts the amount of gas supplied into the storage chamber based on a measured concentration value detected by a gas sensor in the storage chamber, supplying a predetermined amount of gas into the storage chamber; A method for calibrating a gas sensor in an incubator, comprising: calculating a reference concentration value in the storage chamber based on the gas supply amount and the volume inside the storage storage, and correcting the concentration value measured by the gas sensor based on the reference concentration value. .