CH624773A5 - Error compensation method for a measuring instrument for detecting and processing analog electrical quantities or quantities transformed into such. - Google Patents

Description

The invention relates to an error compensation method for a measuring device for recording analog electrical or converted into such variables, which is assigned to an energy distribution network, which converts analog variables into digital values and whose measured values are calculated by a computer with an assigned non-volatile memory.

Error compensation methods for measuring devices and measuring devices are known. For example, DE-OS 22 08 732 a system of measurement, control and regulation technology, in which major interference influences of the measurement lines or cables e.g. determined by electrical and magnetic field influences by interlocking circuits and interference signaling devices and are not fed to the computer to avoid wrong calculations.

Furthermore, DE-OS 21 30 634 shows a compensation arrangement for a measuring device in which the external change conditions, e.g. Pollution, and due to internal influences, e.g. Aging of the measuring element, occurring deviations in the measurement result are taken into account. However, only the measuring element and the components directly assigned to it are taken into account.

The measuring accuracy of measuring devices, e.g. However, energy consumption meters, maximum monitors, etc. generally depend on the properties of many different components. The errors primarily affect the zero point constancy and the calibration, i.e. the slope of the converter characteristic. Numerous methods for automatic zero point and calibration correction are known which avoid these disadvantages mentioned. In the case of a measuring device equipped with automatic zero point and calibration correction, the linearity error of the converter characteristic remains.

In each such measuring device, the reference quantities and often also analog components remain outside the zeroing and calibration control loops. Apart from the fact that when testing such a measuring device, the actual values of the reference values and the components not detected by the zero point and calibration correction can be derived from the respective setpoints using suitable setting elements, there are also temperature dependencies and the age-related drifts.

5 The object of the invention described below is to provide measuring devices which no longer contain any adjustment elements and therefore do not require any adjustment work and in which temperature dependencies and age-related drifts are largely compensated for automatically, io This task is according to the invention by the characterizing part of patent claim 1 solved.

When comparing such a measuring device, the deviations of the components not detected by the zero point and calibration correction and the reference values from their respective target values are determined, and corresponding correction values are determined and taken into account each time when calculating the final measurement result. In this way, re-verifications are possible at any time. The correction values can be checked and saved automatically in the shortest possible time.

In order to largely compensate for temperature influences, temperature coefficients of the components not detected by the zero point and calibration correction and of the reference variables are determined and registered. Such a measuring device 25 also expediently contains a temperature sensor, the output signal of which is processed by the mostly existing analog-digital converter When calculating the final measurement result, the output signal of the temperature sensor and the temperature coefficients contained in the memory are now taken into account.

The last remaining cause of the fault, aging, is largely compensated for by determining and taking into account the aging rates of the components 35 not detected by the zero point and calibration correction and the reference variables. Furthermore, there is a time base, which - derived from a suitable, sufficiently precise frequency - is set to zero when such a measuring device is started up for the first time, and whose respective status is advantageously retained in a corresponding non-volatile memory even if the power supply fails. The current status of the time base and the determined aging rates are taken into account when calculating the final measurement result. In a later re-calibration, the actual aging effects can be determined from the deviations of the components and reference sizes measured at this point in time and stored from their target values, and new values for the aging rates can be registered accordingly. Because of the logarithmic course of aging processes, such a measuring device becomes more and more precise over time.

The above-mentioned linearity error of the converter characteristic of an analog-digital converter in such a measuring device can also be largely compensated by determining a measuring curve from a corresponding number of points and registering it for later consideration in the calculation of the measurement result.

If correction curves have already been determined for other components or reference size, the compensation of the linearity error of the analog-digital converter can be combined with the fact that the correction curve for the other component is not recorded directly on the component itself, but rather by the correction curve of this component over 65 the analog-digital converter is measured and the values are tapped at its output; a correction curve obtained in this way then also contains the errors of the analog-digital converter.

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The described invention is suitable for measuring devices that use a computer. If the user of such a measuring device has suitable reference sizes, such measuring devices can also be designed so that the An624 773

wender only needs to connect the reference values and inform the measuring device with a suitable command that it should calculate new values and replace them with the old ones.

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Claims (3)

624 773 1.Error compensation method for a measuring device for recording analog electrical variables or variables converted into such, which is assigned to an energy distribution network, converts analog variables into digital values and whose measured values are calculated by a computer with assigned non-volatile memory, characterized in that correction values are used to calculate the measured values the reference quantities and all of the components, the properties of which influence the measurement result, and temperature coefficients and types of aging of the reference quantities and components are taken into account, these correction values being measured in each case, including the measuring device's own analog-digital converter, so that they also contain its errors that the measuring device registers the elapsed time since the use of a measuring device by means of time base devices and that the respectively valid aging rate is taken into account. 2. The method according to claim 1, characterized in that the time bases are derived from the mains frequency or a quartz or a freely oscillating oscillator and the current status of the time bases is stored in the non-volatile memory when the power supply fails. 2nd PATENT CLAIMS 3. The method according to claim 1, characterized in that the computer of the measuring device automatically calculates new correction values when connecting other reference values and entering appropriate commands and thus overwrites the stored values.