Solid state radio-measuring optical-frequency transducer of gas flow rate

Abstract

The paper presents a study of a solid state radio-measuring optical-frequency transducer of gas consumption based on a transistor structure with a negative differential resistance. A mathematical model of a solid state radio-measuring optical-frequency flowmeter was developed, which made it possible to obtain the conversion function and the sensitivity equation. The solid state radio-measuring optical-frequency gas flowmeter is based on a transistor structure with a negative differential resistance, consisting of a HEMT field-effect transistor and a bipolar transistor with a passive inductive element. When replacing the passive inductance with an active inductive element, the transducer can be completely integrated. The negative differential resistance formed by the parallel connection of the impedance with the capacitive component on the collector-drain electrodes of the transistor structure and inductance leads to the occurrence of electrical oscillations in the oscillator circuit. Theoretical and experimental studies have shown that with an increase in gas consumption from 0 l/h to 4 l/h, the generation frequency decreases from 812.65 MHz to 811.62 MHz at a supply voltage of 3.3 V, and at a supply voltage of 3.8 V from 813.00 MHz to 811.80 MHz. It is shown that by choosing a constant voltage power supply mode, it is possible to obtain an almost linear dependence of the generation frequency on the gas flow rate and choose channels for transmitting measurement information. The obtained theoretical and experimental studies are in good agreement, the relative error does not exceed 2.5 %.

Keywords

• solid state radio-measuring optical-frequency gas flowmeter
• photosensitive transistor
• negative differential resistance
• frequency
• interferometric refractometry