DIGITAL MEASURING INSTRUMENT

摘要

The digital measuring instrument samples at discrete points in time the analog output signals emitted by a measurement transducer (2) of an electrical supply system in a sample and hold circuit (4), subsequently digitizes the sampled values in an analog/digital converter (5) and then forms a system-specific quantity such as, for example, the root mean square value or the system frequency from the digitized values in a digital processing unit (6). This measuring instrument is intended to be suitable for solving the essential measurement value processing tasks occurring in an electrical supply system in a simple manner and with projectable measurement accuracy. This is achieved by the fact that the digital processing unit (6) exhibits a block (7) for shifting the frequencies (.omega.1, .omega.i) of fundamental and harmonics to 3 direct-current signal (DC) which is proportional to the system-specific quantity and a subsequent filter arrangement (8) with a digital low-pass filter (100) for suppressing the frequencies (.omega.1, .omega.i) deviating from the directcurrent signal (DC) and a digital band-stop filter (110) for suppressing aliasing frequencies. (Figure 1)