PLC analog output module

Patent metadata

Field	Value
Publication number	US-9470723-B2
Application number	US-201214391199-A
Country	US
Kind code	B2
Filing date	Apr 9, 2012
Priority date	Apr 9, 2012
Publication date	Oct 18, 2016
Grant date	Oct 18, 2016

Abstract

As a configuration for detecting an occurrence of abnormalities such as a disconnection of output wiring or an overcurrent of a PLC analog output module that controls a load by an analog current signal, the PLC analog output module includes a current output circuit that outputs the analog current signal, a current sensing resistor provided at a current output terminal of the current output circuit for directly detecting an analog current output to the load, a monitoring circuit that monitors voltages at both ends of the current sensing resistor, and an abnormality detection circuit that discriminates whether there is an occurrence of a disconnection or an overcurrent based on a monitoring result of the monitoring circuit.

First claim

The invention claimed is:

1. A PLC analog output module for controlling a load by an analog current signal, comprising:
a current output circuit that outputs the analog current signal;
a current sensing resistor provided at a current output terminal of the current output circuit and on a side of a higher potential than the load, the load being provided between the current sensing resistor and ground, the current sensing resistor directly detecting an analog current output to the load;
a differential circuit that outputs a differential voltage of voltages at both ends of the current sensing resistor;
an abnormality detection circuit that receives the differential voltage output from the differential circuit and discriminates whether there is an occurrence of a disconnection and an occurrence of and overcurrent based on a determination result as to whether the differential voltage is equal to or lower than a determination value; the abnormality detection circuit using the differential voltage output commonly to discriminate the occurrence of the disconnection and the occurrence of the overcurrent; and
a control module that changes and sets the determination value to be compared with the differential voltage in the abnormality detection circuit.

2. The PLC analog output module according to claim 1 ,
wherein the abnormality detection circuit includes a disconnection discrimination circuit comprised of a comparison circuit that discriminates the occurrence of the disconnection based on whether the differential voltage is equal to or lower than the determination value.

3. The PLC analog output module according to claim 1 ,
wherein the abnormality detection circuit includes an overcurrent discrimination circuit comprised of a comparison circuit that discriminates the occurrence of an overcurrent output based on whether the differential voltage exceeds the determination value.

Assignees

• Watahiki Masataka
• Hoshikawa Masaru
• Takase Shigeaki
• Mitsubishi Electric Corp

Inventors

• Watahiki Masataka
• Hoshikawa Masaru
• Takase Shigeaki

Classifications

• G01R31/50 Primary

  Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections (testing of sparking plugs H01T13/58) · CPC title

• G05B19/048 Primary

  Monitoring; Safety · CPC title

• G05B19/05

  Programmable logic controllers, e.g. simulating logic interconnections of signals according to ladder diagrams or function charts · CPC title

• G05B19/058

  Safety, monitoring · CPC title

• G01R19/1659 Primary

  to indicate that the value is within or outside a predetermined range of values (window) (G01R19/16514, G01R19/16519, G01R19/16528 and G01R19/16533 take precedence) · CPC title