Method for avoiding errors when measuring or determining gas consumption by matter

The present invention relates to a method for avoiding errors in the measurement or determination of the gas consumption of matter, in particular for the measurement of biochemical oxygen demand, arranged in a sealed container sample.

So far, it has been common in these processes to arrange a sample to be measured in a thermostat or air-conditioned space, particularly incubator and leave the containers open to adaptation, ie adjustment of the sample has occurred to the ambient conditions. Then the container including the measuring system was sealed, and it was started with the measurement.

The present invention has the object of providing a reliable avoidance of errors in the measurement of gas consumption of matter, in particular for the measurement of biochemical oxygen demand (BOD measurement) to ensure a arranged in a contained sample to a simple handling, in particular without the already incubator container located again need to be accessed.

The object is achieved by the method of claim. 1

According to the invention, the internal pressure in the container is monitored by the measuring device before the actual start of measurement. In general, in this time is carried out a temperature adjustment of the container contents at the temperature in the incubator, that is to the cold sample is heated to the temperature level of the incubator, in which the container is disposed. Too warm sample cools accordingly. This adjustment of the sample gas is located above the waste is connected to a pressure increase /, which would affect the measurement result with an immediate start of measurement. The measuring device thus monitors the pressure in the container and starts the measurement only when the pressure change due to the temperature adjustment is unimportant and therefore the measured results not distorted significantly. The end of the pressure application is usually recognized by the fact that the relatively high temporal change in pressure passes into a lower rate of pressure change. This time can be determined by an appropriate choice of the predetermined range of values ​​for the rate of pressure change and use it to start the measuring process or for the start of the evaluation of the measurements. Preferably can be used for different samples (filling ratios, container sizes) store different predetermined ranges of values ​​in a reference value memory of the controller, which then allow the use of the measuring device for multiple samples (filling ratios, container sizes) and a sample-specific start of the measuring device. Therefore, when the temporal change in pressure is within the predetermined value range, the measurement is started. At too cold sample that date is deemed to exist if there is no increase in pressure in the container takes place more or the pressure increase initiated through biochemical processes in a pressure drop, ie at the inflection point of the pressure curve.

The advantage of the method is that in the test phase, a temporal reference point is defined, which represents the end of the test phase and the beginning of the measuring phase or evaluable measurements. This reference point defined sufficiently precisely the time at which the biological and physical adaptation of the sampling system (sample + container + measurement system) to the environment is at least substantially completed. Therefore, the sample can be immediately locked in the incubator after filling into the container and after being connected to the measuring system, without the tank again afterwards must be accessed in order to close this. It is of course also possible, the pressure values ​​of the samples in the incubator system simple, as in a measured value recording and carry out the evaluation process of the invention later after completion of the measurement. In this case, the pressure curve is also evaluated according to claim 1, wherein the determined during the evaluation reference point in time is not the start of measurement, but the start of the evaluated measured values ​​defined.

In an advantageous development of the invention can be provided that regardless of the initial state of the measuring system, ie, whether the measurement system is too hot or too cold, before the test phase is provided an adaptation phase, takes place within the not measure nor a pressure rating of the tank pressure , Such an adaptation phase is carried out over a period of 0 to 2 hours, and is preferably at a defined value, for example set to one hour.

Furthermore, it is advantageous if the test phase, is adjustable to a maximum value, for example 2.5 hours. In this way, the examination of the change in pressure is limited after the adaptation period to a sensible total time.

Preferably, the pressure check will min during the test mode at time intervals from 0 to 60. made, which is advantageous when a battery or akkumulatorbetriebene measuring device is used. The time interval is set to an appropriate value that is based on the usual duration of the test phase. There are time intervals between 15 min. and 50 min. prefers. After each time interval, a pressure comparison is made with the last stored measured value. If the current pressure (measurement) value is greater than the last stored pressure value, so the zero point of the pressure measuring system is set to the actual pressure value and a new time interval is started. Only when the pressure after the time interval is less than or equal to the last set zero, the measuring system for the actual measurement is started. The starting value for the automatic measurement of the last zero point of the measuring system is used.

During the measurement phase now running the measurement value at time intervals of 10 sec. made up to 24 h. The time intervals are at a battery or akkumulatorbetriebenen measuring device preferably between 12 and 24 hours.

In another version with external data evaluation, the measurement value can preferably between 5 and 60 min. done.

In an embodiment in which the measuring system is designed as a pure pressure sensing system, the determination of the starting point of the measurement is performed later after completion of the duration of the pressure value detection. Here, the principle of determining the starting point will be applied by analogy to described above simultaneous start point determination in the instant data analysis. The measured value transmission between transducer and evaluation is carried out either after completion of the measurements from the memory of the measuring system off-line or online via line, radio, infrared, ultrasonic or inductive connection.

The method for avoiding errors in the measurement of gas consumption of matter suitable for all types of measurements, in which a substance in a sealed container decreases the pressure or partial pressure of a particular gas in the container. In particular, this method is suitable for measuring the biochemical oxygen demand. At the start of the measurement of the actual pressure value is set as zero value for the following measurement. Foregoing biological and physical adjustments of the audit system thus remain in the evaluation of the measured pressure values ​​for BOD measurement disregarded.