4-20 ma signal isolating circuit and multifunctional isolating transmitter

Abstract

The invention relates to a circuit and a transmitter for isolating 4-20 mA DC signals and belongs to the technical field of signal isolating transmission. The circuit comprises an electricity stealingshunting and sampling unit, a small signal amplifying unit, a core processing unit and one or more signal output units, wherein the electricity stealing shunting and sampling unit steals energy fromsource equipment and samples an input current signal; the small signal amplifying unit amplifies the sampled signal; the core processing unit converts the amplified sampled signal into a correspondingdigital value and a PWM signal; each signal output unit consists of a controllable constant current source unit and a filtering unit, the controllable constant current source is controlled by the PWMsignal to generate a pulse current signal, and the pulse current signal generates a constant current signal in linear relation with current of an input end after passing through the filtering unit. The signal isolating circuit and the transmitter can work normally without independent power supplies, and the circuit is simple in structure, easy to integrate and convenient to produce.

Description

technical field [0001] The invention relates to the field of signal isolation, in particular to a 4-20mA signal isolation circuit and a multifunctional signal transmitter. Background technique [0002] In many current industrial sites and laboratories, data transmission between multiple devices is involved, and many linear data are usually transmitted by 4~20mA DC current. In order to avoid mutual interference between two devices, generally Use a 4~20mA signal isolator for isolation. However, the signal isolators currently on the market generally have the following problems: [0003] 1. Using expensive isolation devices, the price is generally high; [0004] 2. The isolation circuit used has an isolated power supply, and the isolated power supply circuit not only increases the cost, but also occupies a large PCB area, resulting in a generally large size of the signal isolator, which is not conducive to integration. Contents of the invention [0005] In view of the above...

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Problems solved by technology

[0003] 1. Using expensive isolation devices, the price is generally high;

[0004] 2. The isolation circuit used has an isolated power supply, and the isolated power supply circuit not only increases the cost, but also occupies a large PCB area, resulting in a generally large size of the signal isolator, which is not conducive to integration

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