Signal processing in a multi-variable indirect measurement system and its uncertainties is considered. It was proposed to extend the vector method of estimating uncertainties, given in Supplement 2 to GUM for the use to describe the accuracy of instrumental systems for indirect multivariable measurements. A formula for the covariance matrix of relative uncertainties is also given. As the example, the covariance matrix for indirect measurements of the star form circuit resistances from its terminals was determined and influence of of the measurement channels uncertainties are analyzed.

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In this paper some interesting and novel features of a four-terminal (4T) network are presented. A single DC current source (J) is switched over and connected in turns to opposite arms of the four-element bridge circuit. This twooutput circuit with two voltage outputs is called a double current circuit (2x1J). The output voltages are differently dependent on the arm resistance increments and their values are given in absolute and relative units. An original application with two sensors acting as strain gauges and RTD's is presented. Signal conditioning formulas of 2D measurement of deflection and temperature of a cantilever beam are discussed in detail. Some results achieved with the use of the circuit are presented, as well.

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