Posted 10 Oct 2016 Hi, I have a job to upgrade a panel I did a long time ago. The panel already has a FX1n plc and 4 standalone temperature controllers. The plc controls the batching and mixing and the temperature controllers - control the temperature. They now want different actions at different temperatures and so I have ordered an FX2n-TC add-on for the plc. My question - can I piggyback the wires from the pt100 themocouples at the temperature controller terminals into the fx2n-tc or do I have to wire extra wires to the thermocouples and make sure the tc's are the double type. Share this post Link to post Share on other sites
Posted 10 Oct 2016 (edited) You can't piggyback the wires from the pt100's but you can of course use the double or duel output type ones. Do the standalone temperature controllers also have an output of their own (4-20mA etc)? If so you could simply program the controllers to retransmit the values (OK you would have to replace the module you have just ordered). Edited 10 Oct 2016 by Nightfly Share this post Link to post Share on other sites
Posted 11 Oct 2016 Cheers Nightfly. I am virtually sure the temp controllers don't have a 4 -20 mA output. (I read the spec online - they are extra plugin modules) and I have a spare FX2n-4AD as well So I better order some 6 core cable and check the temperature probes are doubles. I knew it was a long shot :) Share this post Link to post Share on other sites
Posted 13 Oct 2016 What do you mean by "double type" PT100? Share this post Link to post Share on other sites
Posted 13 Oct 2016 Just now, Veganic said: What do you mean by "double type" PT100? It’s basically two temperature detectors (resistors) inside the body of a single probe (often called dual, twin, duplex probes etc). Each detector is completely electrically isolated (so it can be fed into separate control systems). Example http://uk.rs-online.com/web/p/platinum-resistance-temperature-sensors/3971416/ Share this post Link to post Share on other sites
Posted 13 Oct 2016 On 10 October 2016 at 3:09 AM, Ron_S said: Hi, I have a job to upgrade a panel I did a long time ago. The panel already has a FX1n plc and 4 standalone temperature controllers. The plc controls the batching and mixing and the temperature controllers - control the temperature. They now want different actions at different temperatures and so I have ordered an FX2n-TC add-on for the plc. My question - can I piggyback the wires from the pt100 themocouples at the temperature controller terminals into the fx2n-tc or do I have to wire extra wires to the thermocouples and make sure the tc's are the double type. PT 100 and TC or thermocouple are two different items. TC can be piggy backed and As Nightfly points out you can't piggy back RTD (PT100) Some controllers can re-transmit. 1 person likes this Share this post Link to post Share on other sites
Posted 14 Oct 2016 The FX2n-TC -ad unit is not the correct one for RTD's you need the FX2n-4ad, you can connect the probes to this and completely do away with the controllers for control and do it all in the PLC (unless that is you need to use the displays) even then, if you have some form of HMI you could display temperatures on that. Steve Share this post Link to post Share on other sites
Posted 15 Oct 2016 I might be misreading something, but I think there are some misunderstandings here: 3-wire PT100 is not the same as dual output PT100. One PT100 sensor can simply be connected using 3 wires (compensated) or 2 wires (a 3 wire sensor can be shorted and then you have a 2 wire sensor) Regarding the modules: FX2N-4AD-TC = J or K thermocouple elements (NOT PT100) FX2N-4AD-PT = PT100 FX2N-4AD = VDC or mA signal Share this post Link to post Share on other sites
Posted 16 Oct 2016 There are some misunderstandings :) and it is my fault. I actually ordered the FX2N-4AD-PT (not TC) it must be because I was setting some thermocouples up last week and the word stuck in my mind. The company have plenty of spare double PT100's (nearly wrote thermocouples again) That's - for clarification 6 terminal PT100's And the reason I asked if they could be piggybacked was the controllers read the resistance of the PT100's and I tried a test with two multi-meters on the same PT100 terminals and read 112 Ohms on both. Share this post Link to post Share on other sites
Posted 19 Oct 2016 On 10/13/2016 at 10:20 AM, Nightfly said: It’s basically two temperature detectors (resistors) inside the body of a single probe (often called dual, twin, duplex probes etc). Each detector is completely electrically isolated (so it can be fed into separate control systems). Example http://uk.rs-online.com/web/p/platinum-resistance-temperature-sensors/3971416/ Thanks for the information. I've not seen those before. Share this post Link to post Share on other sites