Quick relay protection method and circuit for current type transmitting signal input channel

Abstract

The invention discloses a quick relay protection method and a quick relay protection circuit for a 4-20mA or 0-20mA current type transmitting signal input channel, and belongs to the field of industrial automation and aerospace measurement and control. Different from the conventional current input signal protection method using a voltage stabilization diode and a self-recovery fuse the method introduces a protection circuit based on feedback control; an often-closed contact of a high-speed signal relay is connected in series to a circuit in front of a current signal input sampling resistor, and voltage on the sampling resistor is fed back to a voltage comparator; when the input voltage is higher than a system safety reference, the comparator generate a signal relay driving signal, and a relay coil is powered on, so that a current ring is cut off, and a sound-light alarm is sent out; therefore, an input analog-to-digital converter (ADC) is quickly protected, so that the ADC is prevented from being damaged by overcurrent and short circuit of the input channel; and the method is faster and more reliable than the conventional method.

Description

technical field [0001] The fields involved in the present invention are industrial automation detection and control, and the field of aerospace measurement and control, specifically the protection of the ADC input channel of the current-type transmission signal. Background technique [0002] In the automation technology in the fields of electric power, petroleum, chemical industry, metallurgy and aerospace, the signal transmission of sensors and transmitters is widely used in the way of two-wire current signal to increase the transmission distance. The signal transmission mode of two-wire current type transmitter includes 0~20mA, 4~20mA and HART bus and other forms. However, the environment in the industrial site is very harsh, there are many interferences, the transmission line is long and even spans multiple factories or workshops, and the human factors are relatively complicated, which makes it easy to cause overcurrent or even a short circuit in the signal circuit during...

AI Technical Summary

Problems solved by technology

However, in actual industrial applications, the on-site ambient temperature is complex and changeable, and the self-recovery fuse is made of PTC material. If the ambient temperature is not suitable, it will not immediately produce protection even if it is over-current, which reduces the real-time and fast protection. Thirdly, practice has found that in industrial situations, due to the complexity of the situation, the Zener diode itself is easily damaged when the current flowing through the circuit is too large, which not only fails to protect but reduces the reliability and stability of the system ;Another problem is that the sampling resistor is connected to the Zener diode in parallel. When the signal is normal but large, the diode impedance decreases, causing a large diode shunt and bringing errors to the precision detection system.

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