Multichannel Generator Time-To-Pulse Converter of the Telemetry Temperature Measurement System

Abstract

The article considers the multichannel time-to-pulse intermediate converter as a part of telemetric temperature measurement system. The principle of operation is based on the use of aperiodic transient in a first-order circuit formed by resistance temperature device and capacitor. Switching of resistance temperature device in the process of temperature measurements is carried out by MIS keys (metal-insulator-semiconductor) according to the signal from the output of the circuit, and the allocation of the output information interval is carried out by a voltage comparator. The article illustrates an electric circuit of a time-to-pulse converter. Based on the equivalent scheme, the main metrological characteristics were obtained by calculation, namely, the dependences of the sensitivity of the output value of the converter to changes in the parameters of the circuit elements expressed in terms of temperature. The scheme of a time-to-pulse converter with an optical output, designed for use with semiconductor resistance temperature devices was experimentally investigated. Variants of multichannel converters for 7 and 15 measuring channels are implemented. Digital elements of the MIS-type (metal-insulator-semiconductor) are used. Information about the temperature at the output of the converters was encoded in the duration of 128 periods of pulse signals, which ensured reliable of information intervals in the receiving part of the equipment. A laboratory tester with an optoelectronic input was used as a receiver of optical pulses. The duration of the information intervals was measured by an industrial measuring device with a resolution of 10 billiseconds. The experimental and rated characteristics of the conversion and the dependence of the conversion error on the supply voltage, operating temperature and resistance of primary thermal converters are presented. It is established that in terms of the main operational parameters, a generator-type time-to-pulse converter is not inferior to a circuit with external excitation. At the same time, the generator converter is less sensitive to the errors of the comparator in terms of electrical bias and speed. The use of a multichannel generator time-to-pulse converter is advisable in telemetric temperature measurement systems when transmitting information in a communication channel during the duration of the period of information, in particular, optical pulses.