Digital quantity output device of programmable logic controller and self-checking method

Abstract

The invention provides a self-checking method for a digital quantity output device of a programmable logic controller, and the method comprises the following steps: collecting the digital quantity output when a driving switching tube is in a turn-on state/off state in the digital quantity output device according to a selected signal transmitted by an I/O (input/output) module processing unit in the digital quantity output device; carrying out a differential operation to the collected digital quantity output and the supply voltage of the driving switching tube to obtain a simulation signal forrepresenting the turn-on voltage drop/electricity leakage judgment parameter of the driving switching tube; converting the simulation signal into a digital signal; and comparing the digital signal with the turn-on voltage drop parameter value of the driving switching tube/the voltage value which is the same to the power supply of the driving switching tube, thereby judging whether the driving switching tube is aged or not. Correspondingly, the embodiment of the invention also provides a digital quantity output device of a programmable logic controller. According to the digital quantity outputdevice provided by the invention, the recession conditions of the driving switching tube can be known in advance, and users can perform equipment maintenance before cataleptic failures.

Description

technical field [0001] The invention relates to the field of automation control, in particular to a programmable logic controller digital quantity output device and a self-checking method. Background technique [0002] The digital quantity (switch quantity) controlled by the programmable logic controller (PLC, Programmable Logic Controller) is used in a medium-scale system with more than 1,000 points, of which the output points account for about half, so the reliability of the digital output is related to the whole. The reliability of the automation application system, and some of these digital output points control the key equipment parts of the system, and the system has strict requirements on the reliability of the output points of these important parts. [0003] In the prior art, digital output points are generally controlled by power switches, and the reliability of these output points is basically determined by the durability of the power switch. When the power switch ...

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Problems solved by technology

[0004] However, the above approach is a response only when the output point has failed. At this time, it has often caused irreparable losses to industrial production.

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