Multimeter

Abstract: This article outlines new low-cost hardware set-ups as viable substitutes for conventionally employed cost-intensive impedance analyzers/LCR meters for implementation of the electro-mechanical impedance (EMI) technique for SHM/NDE. The proposed solutions warrant basic low-cost equipment, such as function generator and digital multimeter, which are commonly available in most laboratories. Unlike the case of impedance analyzers/LCR meters, only the absolute admittance (i.e., magnitude) is measured. A simple computational approach is outlined for effective utilization of the absolute admittance function for SHM after filtering the passive component. Comparison of results with LCR measurements shows that the measurement accuracy of the proposed set-up is fairly good, repeatability excellent, and the damage sensitivity comparable to that of the cost-intensive conventional hardware. The proposed adaptation is, therefore a suitable candidate for the widespread industrial applications of the EMI technique.

Abstract: A multimeter with variable color digital display indicates measured values in a digital format and in a variable color. The multimeter includes a color control circuit for controlling the color of the digital display in accordance with the measurement quantity, method, unit, mode, function, range, location, modifier, control, limits, and the like. A color converter circuit is disclosed for converting analog voltage to variable color.

Abstract: A new generation of multipurpose measurement equipment is transforming the role of computers in instrumentation. The new features involve mixed devices, such as analog-to-digital and digital-to-analog converters and digital signal processing techniques, that are able to substitute typical discrete instruments like multimeters and analyzers. Signal-processing applications frequently use least-squares (LS) sine-fitting algorithms. Periodic signals may be interpreted as a sum of sine waves with multiple frequencies: the Fourier series. This paper describes an algorithm that is able to fit a multiharmonic acquired signal, determining the amplitude and phase of all harmonics. Simulation and experimental results are presented.

Abstract: A multimeter having an elongated housing with a fixed recess for receiving a current-carrying conductor is provided. The multimeter is adapted to measure various parameters including a.c. and d.c. voltage, resistance, and a.c. current. On one end of the elongated housing of the multimeter is a C-shaped current sensor mounted around the fixed recess for measuring a.c. current in the current-carrying conductor and on the other end is a pair of test leads for measuring resistance, a.c. voltage, and d.c. voltage. The current sensor and the test leads provide input signals to an analog-to-digital converter (ADC) to obtain digital samples which are displayed as measurement results according to the selected measurement mode.