Two-wire system instrument and two-wire system instrument control circuit

Abstract

The invention discloses a two-wire system instrument and a two-wire system instrument control circuit, and aims to realize a backlight function of an LCD (Liquid Crystal Display) screen in the two-wire system instrument, and the two-wire system instrument is not provided with a DC-DC (Direct Current-Direct Current) voltage converter in the prior art. The voltage stabilization driving module and the backlight module in the two-wire system instrument are connected in parallel, a circuit after parallel connection is connected with the impedance adjusting module in series through a signal transmission line, and finally the two-wire system instrument is connected with a power supply and sampling impedance in a control circuit of the two-wire system instrument in series, so that the backlight function of the LCD display screen is achieved. Compared with the prior art, the two-wire system instrument has the advantages that the production cost of the two-wire system instrument is reduced on the basis of ensuring the design requirement of the maximum current consumption of the two-wire system instrument, and the problem that analog signals output by the two-wire system instrument in the prior art are influenced by electromagnetic interference generated when the added DC-DC voltage converter works is solved; therefore, the conversion precision of the two-wire system instrument is improved.

Description

technical field [0001] The invention relates to the field of instrument design, in particular to a two-wire instrument and a two-wire instrument control circuit. Background technique [0002] Two-wire instruments include two signal transmission lines for transmitting a standard analog signal of 4-20 mA and these signal transmission lines themselves also serve as power supply lines. When in use, the instrument needs to be connected in series with the power supply and impedance through the analog quantity transmission channel. While ensuring its own power supply, it realizes the function of converting physical quantities such as temperature and pressure to be detected into 4-20mA standard analog signals. In order to realize its own normal operation and comply with the minimum standard analog signal transmission requirement of 4mA, the maximum current consumption of the instrument must be controlled below 3.5mA. [0003] In order to enable the LCD (Liquid Crystal Display, liqu...

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Problems solved by technology

[0004] The purpose of the present invention is to provide a two-wire instrument and a two-wire instrument control circuit, which reduces the production cost on the basis of ensuring the design requirements of its own maximum current consumption, and solves the problem of the two-wire instrument in the prior art. The analog signal output by the instrument is affected by the electromagnetic interference generated by the added DC-DC voltage converter, which improves the conversion accuracy of the two-wire instrument

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