JPH0350978B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for automatic zero point adjustment of a thermal conductivity measurement cell in an aerated culture tank.

The aerated culture tank covered by this specification is described, for example, in German Patent No. 2924446 (U.S. Patent No.
4336329). but,
The present invention is not limited to the structure and embodiment of the culture tank described in the specification.

(Prior Art) Conventionally, in measuring devices, in particular measuring devices for the measurement of CO ₂ concentration in the working chamber, it is generally necessary from time to time to adjust the zero point of the device, and in some cases to correct the zero point. It was necessary.

(Problem to be solved by the invention) When measuring gas concentration in an aerated culture tank, it takes several days.
Long measurement cycles lasting weeks and months are used and the atmosphere within the tank must be checked continuously to maintain the desired process conditions. The gas atmosphere inside the tank is controlled by a thermal conductivity measuring cell, but the gas concentration measuring sensor may become contaminated or aged due to long-term use of the cell, and may no longer indicate an accurate value. Therefore, it is necessary to modify the output signal of the cell from time to time so that the cell does not provide an output signal that is incorrectly indicative of the gas concentration within the bath. Since the culture vessel has to be sealed in order to be sterile, direct access to the measurement side is not possible, for example when calibrating the cell. Therefore, cells must be self-modifying or self-adaptive. In the case of long measurement cycles, such as weeks or months, a system and method for testing the measuring cell during such long-term operation, i.e. the output signal of the measuring side and the output of the reference side under the same conditions (atmosphere). Of particular importance is the provision of a means to compare the signals.

The object of the invention is to provide a simple and automatic method for adjusting zero point fluctuations in order to eliminate their possible influence on the measuring system and thus on the CO ₂ concentration. be.

(Means for Solving the Problem) The problem of the present invention is to adjust the zero point of the thermal conductivity measurement cell in an aerated culture tank containing CO ₂ gas in the working chamber atmosphere, which can be adjusted by the thermal conductivity measurement cell. (a) during the calibration step, the reference side of the measuring cell is aerated to the working chamber atmosphere while the working chamber atmosphere is continuously exposed to the measured values of the measuring cell; (b) during said calibration step; (c) measure and store the difference between the output signals of both the verification side and the measurement side as the output signal or deviation correction value obtained during the measurement step; , algebraically added to the output signal obtained from the measurement side of the measurement cell when the reference side of the measurement cell is aerated with reference gas in the next measurement cycle. This is achieved by providing a method.

In addition, in (c) above, "algebraically adding" means adding (plus) when a positive misalignment correction value is obtained, and subtracting (minus) when a negative misalignment correction value is obtained. It means that.

Constituent features of the present invention other than those described above are as described in claims 2 to 4, the description of the embodiments, and the explanation of the drawings. It is obvious that the embodiments of the invention may be modified without departing from the spirit of the invention.

In particular, known features, e.g. German patent no.
All combinations with elements known from document 2924446 are included in the invention.

The method according to the invention is carried out in an embodiment using conventional electronics to initiate the operation. A measurement phase then takes place, starting with a measurement with a thermal conductivity detector and then reading the measurement results.

A calibration step is then performed, and after the calibration step a zero point correction is performed. Finally, these processes are programmed, for example, by a small computer or microprocessor, and the child is asked whether the zero point is OK and the answer is yes or no.
If the answer is yes, repeat the above operation, and if the answer is no, the next step is to measure the error and then send a correction signal. The correction signal is stored and the stored signal is returned after the nearest previous calibration step to perform the zero point correction.

The figure is an explanatory diagram of an embodiment of the present invention.

FIG. 1 is an operational process diagram of the present invention. FIGS. 2A and 2B are schematic explanatory diagrams showing a thermal conductivity measurement cell and lines connected thereto.

The measuring cell has a measuring side 2b and a verification side 2a. In FIGS. 2A and 2B, the direction of gas flow is indicated by arrows. That is, in FIGS. 2A and 2B, the gas flow during the measurement stage is shown by a broken line, and the gas flow during the calibration stage is shown by a solid line.

During the measurement stage, the gas atmosphere is introduced into the measurement cell through the 2m inlet pipe, and the gas atmosphere is introduced into the measurement cell through the 2m inlet pipe,
b is constantly in contact with the gas atmosphere in the working chamber, and the gas concentration is measured. On the other hand, the air pump 2 is on the verification side 2a.
6 directs the air through a sterilization filter 27 and a solenoid valve 29 or Y-shaped element 31.

In the calibration stage, the air pump 26 is stopped and atmospheric gas is introduced into the verification side 2a by the rotating fan 30. In FIG. 2A, a portion of the gas atmosphere flows through the conduit 28 and the open solenoid valve 29 to the reference side 2a of the thermal conductivity detector 2 due to the actuation of the rotating fan 30. In FIG. 2B, a portion of the gas atmosphere is sucked through the reference side 2a of the thermal conductivity detector 2, the Y-shaped member 31 and the throttle valve capillary 32 by means of the rotating fan 30.

The difference between the output signal obtained from the verification side 2a and the output signal from the measurement side 2b by introducing the gas atmosphere is measured and stored. If the difference between the output signals at the terminal 2s is not zero, for example, a positive or negative deviation correction value (i.e., the difference between both output signals) for the verification side is obtained, and this deviation value is then used for measurement cycles. Due to deviations on either the measurement side or the reference side, a zero point correction signal is obtained and is used for the next measurement before entering a new calibration phase.

Thus, during the measurement phase the gas atmosphere is applied to the measurement side and the reference gas is applied to the reference side, and during the calibration phase the gas atmosphere is applied continuously to the measurement side of the measurement cell while Since the reference side of the sensor is exposed to a gas atmosphere and the output signal is measured and stored, there is no need to interrupt operation during measurement.

FIG. 3 shows a culture tank known per se from German Patent Publication No. 2924446, with a thermal conductivity detector 2 in the bypass 1. The method of the invention can be applied to the zero point adjustment of the measuring cell in this culture tank.

As shown in FIG. 3, the aerated culture tank includes an electronically controlled biocompatible atmosphere in the working chamber 10, which approximates in vivo conditions. In this case, the composition of the atmosphere, especially with regard to the components and component proportions of the gas mixture of the atmosphere, can vary considerably, especially when the gas mixture further contains oxygen (or air) and water vapor besides _CO2 . The relative humidity, temperature and content of these gases can be varied in a controlled range, thereby also making it possible to adjust the PH value, for example by adjusting _CO2 , according to the Henderson-Hatsselbach equation. Yes, and advantageous.

CO ₂ in the bypass 1 thermally connected to the working chamber 10
Measuring elements such as a gas concentration measuring probe (thermal conductivity detector 2), a circulating flow temperature measuring probe 3, a humidity measuring probe 4, and, if necessary, an oxygen gas detection electrode and a pH value detection electrode are arranged. . In particular, the electrodes for detecting oxygen gas and the electrodes for detecting the pH value may be arranged elsewhere, preferably in the liquid medium in the working chamber 10.

The working room may be, for example, as described in detail below.
CO ₂ is selectively vented in a controlled manner from a source of air or oxygen or nitrogen via a pressure reducing valve;
These gases can be passed individually or together to conduit 8.
The water vapor from the conduit 7 in the bypass 1 was superheated and sterilized in the evaporator 20 outside the culture tank. It was then cooled down.

The culture tank 10 and the double casing 11 are surrounded by a heat insulating layer 11a, and are further shielded from the outside with a moisture-proof coating, such as aluminum foil, to prevent the permeation of external air and the cold and warm zone from getting wet. protected. Circulation of the air in the intermediate chamber in the double casing 11 is preferably effected by an air flow 12 extending over the entire cross-section of the double casing 11. On the inner wall of the double casing 11, and thus on the wall attached to the working chamber 10, heating elements 13, in particular electric heating elements and cooling pipes 14 are preferably arranged in a symmetrical arrangement, ie uniformly distributed over the entire periphery of the casing. There is. The double casing 11 thus ensures that the working chamber 10 has a very uniform temperature, so that despite the high temperature inside the working chamber the dew point is not reached.

Humidity regulation uses a suitable standard circuit regulated by a psychrometer, which is coupled via a control conduit to a pump 15 which introduces, for example, deionized water from a reservoir 19 into an evaporator 20; The water is evaporated in this evaporator 20 and sterilized by heating to a temperature of 100° C. to about 500° C., then led to the bypass 1 and circulated through the working chamber 10. A psychrometer consists of a dry thermometer and a wet thermometer, for example a resistance thermometer, in which case the wet thermometer has a wick which projects into the suction cup and these parts are connected to the bypass 1.
will be placed in

The psychrometer is placed in the bypass, preferably at a narrow cross-sectional area, such that the measuring probe of the wet thermometer determines the optimum flow rate of the circulating medium. A probe for measuring the concentration of CO ₂ gas (thermal conductivity detector 2) and a probe for measuring the temperature of the circulating flow 3 are arranged in the bypass 1.

The CO ₂ regulation takes place in a regulation circuit in which the CO ₂ concentration measuring probe is a thermal conductivity measuring cell. The measuring cell consists of a measuring side 2b and a reference side 2a, in the measuring phase the measuring side is continuously exposed to the gas atmosphere inside the working chamber, while the reference side is exposed to air or another gas of known composition, i.e. Washed with reference gas.

If the thermal conductivity of the working chamber atmosphere changes, cooling the measurement probe separately will reduce the thermal conductivity in the atmosphere.
An electrical signal is generated depending on the percentage of CO ₂ . This signal is sent directly to a regulating device, for example to operate a valve 36 regulating the supply of _CO2 .

In the case of temperature regulation, a platinum resistance measuring device Pt100 and a regulator with PID characteristics are preferred as temperature measuring probe 3, which regulator can be connected to a time-temperature program transmitter. The cooling trap 5 is equipped with a defrosting heater 5a and a collection gutter 5b, and the generated condensed water is guided to a receiver 24 equipped with a water level detector 24a, from which it is sometimes sucked by a pump 23 as needed and evaporated. It is guided into a container 20 and released into the atmosphere.

The evaporator 20 is preferably in the form of a tubular furnace, and the peripheral surface of the furnace is equipped with an electric heating device for heating to a predetermined temperature. Furthermore, the steam introduction line from the evaporator 20 to the bypass 1 is equipped with a condensing device 25 (tubular coil) and a solenoid valve 22.

(Effects of the Invention) The present invention has various advantages. In particular, it does not produce results that vary depending on the CO ₂ measurement cell. The method of the invention eliminates the need for periodic zero adjustments and re-corrections due to variations in working temperature. For example, it is possible to install it in an existing aerated culture tank by replacing the gas analyzer.

[Brief explanation of drawings]

Figure 1 is an operational process diagram of the present invention, Figure 2A is a schematic diagram of the thermal conductivity measurement cell and conduit connections, and Figure 2A is a schematic diagram of the thermal conductivity measurement cell and conduit connections.
FIG. B is a schematic diagram of a modified embodiment of the thermal conductivity measurement cell of FIG. 2A, and FIG. 3 is a schematic explanatory diagram of an aerated culture tank equipped with a thermal conductivity measurement cell. 1: Bypass, 2: Thermal conductivity measurement cell (detector), 2a: Verification side, 2b: Measurement side, 2m: Inlet pipe, 2s: Terminal, 3: Temperature measurement probe, 4: Humidity measurement probe, 5: Cooling Trap, 5a: Defrost heater,
5b: Collection pipe, 6: Blower, 6a: Inlet, 6
b: Outlet, 7: Conduit, 8: Conduit, 8a: Sterilization filter, 9: Preheater, 10: Working chamber, 11: Double casing, 11a: Heat insulation layer, 12: Air flow, 1
3: heating element, 14: cooling pipe, 15: pump, 1
9: Storage tank, 20: Evaporator, 22: Solenoid valve, 23:
Pump, 24: Receiver, 24a: Water level detector, 2
5: condensing device, 26: air pump, 27: sterile filter, 28: conduit, 29: solenoid valve, 30: rotating fan, 31: Y-shaped member, 32: throttle valve capillary, 36: valve.

Claims (1)

[Claims] 1. A method for adjusting the zero point of a thermal conductivity measuring cell in an aerated culture tank containing CO ₂ gas in the working chamber atmosphere that can be adjusted by the thermal conductivity measuring cell, comprising: (a) calibration; During the step, the reference side of the measuring cell is aerated to the working chamber atmosphere while the working chamber atmosphere is continuously applied to the measuring side of the measuring cell; (b) the output signal or deviation obtained in the said calibration step; (c) during the measurement phase, the stored deviation correction value (positive or negative) is used by the reference side of the measuring cell for the next A method for zero point adjustment of a thermal conductivity measurement cell, characterized in that the zero point adjustment method of a thermal conductivity measurement cell is algebraically added to an output signal obtained from the measurement side of the measurement cell when aerated with reference gas in a measurement cycle. 2. The method according to claim 1, wherein continuous measurement of CO ₂ content for calibration is interrupted for automatic zero point adjustment of the measurement cell. 3. The method according to claim 1 or 2, wherein at least a part of the gas or gas mixture constituting the working chamber atmosphere is passed through the thermal conductivity measurement cell in the calibration step in the opposite direction to the measurement step. Method. 4. A method according to any one of claims 1 to 3, comprising continuously flushing the reference side of the thermal conductivity measuring cell with air or other reference gas of known composition during the measurement step. Method.