The Precise Temperature Measurement System with Compensation of Measuring Cable Influence

The article presents an active bridge system that enables the solution of a significant problem consisting in ensuring correct indications of temperature values in a wide measuring range for a Pt100 temperature sensor with properties defined by the standard (EN-60751 + A2). The presented active bridge system combines the properties of the measuring amplifier with the stabilization of the current value in the branch in which the Pt100 sensor was placed. The article focuses on the comparison of the temperature measurement in a typical resistance bridge and the measurement made in the developed active bridge, which has also become the subject of a patent. For the performed tests, in which the correctness of the temperature measurement system operation was verified, and on the basis of the obtained results, the quality of temperature measurements was compared in a wide range of changes.

Simulation of the Analogue Interface for Remote Measurements Using Multiplexer and Resistive Strain Gauges

The simulation of the analog interface circuit based on the measuring amplifier with differential inputs and the ultrasonic scheme and algorithm of non — destructive additive — multiplicative correction have been made. Such schematic of the analog interface reduces the influence of input correlated noise of operational amplifiers and network drives on the «general» resistance. The Fig. 1 shows us the Schematic of the electrical functional analog interface for remote measurement using multiplexer and resistive strain gauges, which contains a measuring chain, a transmitter, the input of which is connected to a DC source through an analog demultiplexer, and the outputs of the measuring chain through the analog multiplexer are connected to the measuring amplifier, and a two-channel analog-digital converter with simultaneous sampling. The measuring chain is made in the form of three resistive current dividers, where one divider is formed by a resistive strain gauge and adjusting resistor, and two others — exemplary resistors. At the Fig. 2 we can see the electric model of the measuring channel in the software Elektronic Workbench. From the analysis of the simulation results it was found that the random additive component of the error would dominate. Since in the simulation of the only random component of the error there is a quantization error, the use of the differential method of measuring the output voltage will significantly improve the metrological characteristics.

The Analogue Interface for Remote Measurements Using Multiplexer and Resistive Strain Gauges

An analogue interface circuit that contains a mea­suring chain, a transmitter, the input of which is connected to a DC source through an analog demultiplexer, and the outputs of the measuring chain through the analog multiplexer are connected to the measuring amplifier, and a two-channel analog-digital converter with simultaneous sampling is developed. The measuring chain is made in the form of three resistive current dividers, where one divider is formed by a resistive strain gauge and adjusting resistor, and two others — exemplary resistors. This work is aimed at finding possibilities for increasing the accuracy of measurements and interfering analog interfaces for remote measurements using resistive strain gauges by introducing a new structural scheme, which is shown on the Fig.2.