DOI: 10.34808/e8n8-ex94
title: Experimental Study of the Influence of Noise Level on the Uncertainty Value in a Measurement System Containing an Analog-to-Digital Converter

description: For newly developed measuring systems it is easy to estimate type B uncertainties based on the technical data of the measuring modules applied. However, it is difficult to estimate A type un-certainties due to the unknown type and level of interferences infiltrating into the measuring sys-tem. This is a particularly important problem for measurements carried out in the presence of typ-ical of power grids disturbances. The aim of the research was to develop a method and a measurement stand for experimental assessment of uncertainties in a measuring system which makes use of data acquisition modules containing analog-to-digital converters (ADCs). The data set presents in detail the design of a completed test stand, and an original application in the LabVIEW environment, which enables testing the dependence of the uncertainties with the quantity of the measurements averaged in a series, for different kinds and levels of interferences infil-trating into the measuring path. Test results for several popular measuring modules are presented. An analysis of the determined uncertainties was carried out in relation to the parameters of the tested measuring modules and for various levels of interferences. It is proved that an increase in the quantity of averaged measurements to approx. 100 ÷ 200 always results in a decrease in un-certainty for each tested module and in all conditions. However, a further increase in the quantity of measurements, even up to 1000 averaged measurements, proved reasonable only for high ac-curacy modules, in particular with a high level of interferences. An excessive increase in the quantity of averaged measurements proved of a low effect for modules characterised by a low resolution and with a low level of interferences. The measurement results proved also that when estimating uncertainties the interference probability distribution is significant, especially if it deviates from the normal distribution.  Schematic diagram of the measurement system  View of the measurement stand: 1- NI USB-6008 module; 2- NI USB-6001 module; 3- NI USB-9215 module; 4-NI-USB-6341 module; 5- REF102 reference voltage source; 6-power supply line 230 V; 7-ferromagnetic core FC; 8-signal wires; 9-USB cables; 10-computer controlling measurements; 11-application in LabVIEW environment.  Left panel part of the LabVIEW application: (a) Data configuring measurements and uncertainty calculations; (b) Results of measurements and calculations in a single series of measurements; (c) Results of calculations of statistical parameters for repeatedly repeated series of measurements.
Right panel part of the LabVIEW application: (a) Results of statistical parameter calculations for repeated multiple measurement series; (b) Results of the root of the number of measurements and its verification from measurements; (c) Results of measurement uncertainties type A, type B and expanded uncertainty U; (d) Histogram of measurement results from a single series.  Flowchart of the program performing the measurements: (a)-internal loop performing a series of single measurements; (b)-loop repeating successive series of measurements; (c)-main loop modifying the number of measurements in the series.