Optimization of the structure of the unified multichannel interface temperature control module for measuring instruments of spacecraft

In the development of a unified multi-channel interface temperature control module for measuring instruments, built on a main-modular principle on the basis of the central instrument module and used on spacecraft for various purposes, the primary task is to determine its structure, which allows to provide temperature control on the elements of the spacecraft design in different measurement ranges and with different requirements for accuracy and stability of measurement. The article is devoted to the analysis of general requirements to the structure of the multi-channel interface temperature control module, in which the measuring channels can have different technical characteristics, and the choice of variants for measuring the resistance of thermal converters to ensure the elimination of the systematic component of the measurement error. It is shown that in the structure of a unified multichannel interface temperature control module there should be a multichannel measurement scheme forming several measurement channels with different technical characteristics operating on a common channel of analog-to-digital conversion. To match the measuring channels with different input resistances and operating in different measurement ranges with the common channel of the analog-to-digital converter, it is necessary to use a controlled normalizing amplifier. To eliminate the systematic component of the measurement error, it is necessary to use three- or four-wire variants of the measurement schemes of thermal resistance converters, which allow the automatic compensation of the measurement error introduced by the resistances of the wires of the communication lines of the measuring cables, and the automatic calibration of the measurement error introduced by the measuring channels. To compensate for the nonlinear component of the measurement error introduced by thermal resistance converters, it is necessary on the basis of piecewise linear approximation of their nominal static characteristics to divide the operating ranges of measurement into subranges and to carry out automatic calibration measurement errors in each subrange separately.