Application of Passive Time-to-Pulse Converter in Temperature Measurement Systems of Moving Objects

Abstract

A variant of the implementation of a time-to-pulse converter as part of a human temperature measurement system is considered, in which a first-order circuit forming an information time interval is formed by a resistance temperature device and a capacitor. Initialization and registration of the time for the transient phenomena are carried out by MIS transistor and an integral comparator. Assessment of the differential sensibility of the converter depending on the time constant of the forming circuit for medium-speed keys is provided. The scheme of a multichannel converter is presented, with sequential and cyclic resistance of several thermal converters into the duration of the impulse response. At the same time, to decrypt the number of the measuring channel, the conversion cycles are separated by pauses. The function of converting temperature into the duration of the time interval is derived for a nickel resistance temperature device based on an equivalent electrical circuit of a time-to-pulse converter. Analytic forms are obtained to assess the effect of inaccuracy of circuit elements and destabilizing factors on the temperature measurement error. The conditions for its reduction have been determined. The converter connection is investigated in the Micro-Cap circuit simulation environment. The discrepancies between the experimental and calculated values of the conversion function did not exceed 0.2%. The temperature instability of the output information intervals of the time-to-pulse converter was no more than 0.1% in the operating temperature range 0 ...50°C and is due to the voltage temperature drift of the comparator bias voltage. The use of a passive time-to-pulse converter is advisable in telemetry systems for measuring temperature or other physical quantities with primary resistance, capacitance or inductance converters forming a first-order circuit in the conversion path. The presented analytical expressions can be used to estimate the additional measurement error.