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Electrical Connection to Redundant Analogue Input Channel

Created by: RoySamia at: 7/26/2009 5:24 PM (1 Replies)

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7/26/2009 5:24 PM	Rate (0)
RoySamia Posts: 11 Rating: (0)	Dear All Issue: Electrical connection to analog redundant HART channel with the ET200iSPConfiguration: We are using the following configuration:- 2 Redundant CPU 414-4 H (6ES7 414-4HM14-0aB0 Firmeware V.4/5) - 2 ET200iSP IM152-1 (6ES7 152-1AA00-0AB0 Firmeware V2.0)- AI cards: 4 AI 2WIRE HART Project requirement: For each pair of redundant analog channel, we only have ONE HART device. Each analog signal must be read simultaneously in two ET200ispAnalog input channels We are using 2 wires HART devices We must read the 4-20mA signal of the HART device(no need for secondary HART values) The HART device must be accessible through the analog channel of the ET200iSP through the PDM software. Problematic:Connection to the AI HART channel signal has been done in series with appropriate zener diodeAs per document ‘wiring connection for red AI with HART.pdf’ Is it correct that each analog channel of the AI module (6ES7134-7TD00-0AB0) is feed by an internal power supply? Is it problematic to connect the two analog channels as per the attached document, it means in series with appropriate zener diodes? Is there any hardware switch on the analog module 4 AI 2 Wire Hart (6ES7 134-7TD00-0AB0) to enable / Disable internal power supply? Even if this serial connection allows us to read the 4-20mA of the HART signal in series trough the 2 channel, does this connection allow the PDM software to access the HART device through the AI channel? Can anybody helps Regards Attachment wiring connection for red AI with HART.pdf (544 Downloads)
RoySamia Posts: 11 Rating: (0)
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8/13/2009 11:48 AM	Rate (0)
dmertens Bronze Member Joined: 10/3/2007 Last visit: 6/25/2024 Posts: 188 Rating: (34)	The electrical diagram looks OK to me, also it answerssome ofyour questions: 1. As you can see on the drawing, the L+ of the instrument is not provided by the module, but is a seperate 24V supply (obviously provided by an Ex rated supply as per the requirement of your application). 2.Redundant analog inputs are allways wired in series, how could the same 4-20mA signall pass trough both channels otherwise? The zener diodes in this diagrammakesure the hart communication electronics gets a high enough voltage even if one of the chanels is open or short circuited. They do not affect the normal 4-20 mA signal in any way. 3. Passive or active (4 wire versus 2 wire operation in siemens terminology) can be parametrized in the module. 4. I'm not sure but I think this would have been tested as it should be the basic functionality of this configuration.

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