7/12/2020 7:08 PM | |
Joined: 4/6/2017 Last visit: 3/5/2022 Posts: 5 Rating: (0) |
Hello All, I am using an S7-ET200SP PLC and the AI unit I am using to connect to my J-Type thermocouples is the AI HF 8xRTD/TC 2-wire (6ES7134-6JF00-0CA1). base unit uses A0 The issue is this: In the hardware settings for the Reference junction option whenever I choose "Internal Reference Junction" I get an overflow decimal value of 32767. When I change the option to "Fixed Reference Temperature" I get a reading but the reading changes in the wrong direction when I apply heat to the thermocouple. approximately -147 for ambient temp 24 deg c Now I'm wondering does it help if I get the right base unit or I need any scaling for fixed reference? ------------------------------------------------------------------------------------------ |
Last edited by: Jen_Moderator at: 07/13/2020 07:46:07New subject after splitting |
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7/13/2020 5:29 PM | |
Joined: 3/28/2010 Last visit: 9/21/2024 Posts: 1056 Rating: (213) |
1. You need to pay attention to the notes 1 and 2 related to cold junction compensation or what Siemens calls 'reference junction', in order to get the cold junction temperature measurement needed to compensate for the difference the terminal block connection temperature and the freezing point of water. reference junction notes from the manual The notes It appears that this module ch 0 uses for the reference junction temperature measurement. It is not clear whether one needs to supply the Pt100 needed for that cold junction reference, or whether it is part of the module. 2. The base unit (whatever that is ? ? ) apparently has an effect on how reference junction measurement is accomplished. See this thread which mentions problems related to having the wrong base unit, A0 or A1. Attachmentchannel 0 is the cold junction 'reference junction' for T-C measurements.JPG (183 Downloads) |
Last edited by: danw at: 07/13/2020 17:40:06 |
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