1746-NT4

[Pulsar2003 0]

I'm experiencing with this module for the first time. I've inspired myself with the examples in the 1746-UM007C-EN-P publication. The thermocouple module is in the the slot 5 I use a J thermocouple on hte input 0 and the CJC is on 3. I created the Integer file N10. The first file is set as is: 0000 1100 1010 0000. Type J, PID, Downscale, 60Hz, Celsius, Enable. The second file is set as is: 0000 1100 0000 1111. CJC, Eng units 1, Open circuit zero, 60Hz, Celsius, Enable. With the thermocouple things are fine. I have a SCP running with the output giving a proper value. Input: I:5.0, input min 0, input max 16 383, scaled min -210, scaled max 760. With a 3910 input value I get a 21.5C which is realistic. I put the prob in cold or hot water and the output value changes accordingly. The channel 3 doesn't behave alike. What I believe my problem is the set up and the input min and max as well as for the scaled min and max. Next, I checked the channel output in both channels and the bit 11 is equal to 1. But the lights on the module for each channel doesn't light up. Bit 11 on should set the respective channel lilght on. I should have channel 0 and 3 on. The module's green light is on though. Thanks again. Edited 29 Nov 2009 by Pulsar2003

[Mickey 71]

You connected the CJC to channel 3? If so the CJC does not connect to any channel see picture below. The CJC is not a thermocouple so connecting it to channel 3 will not work.

[Pulsar2003 0]

No I didn't I left it to it's own connection. Only channel 0 has a J thermocouple, the others are not used. Edited 29 Nov 2009 by Pulsar2003

[Mickey 71]

Well, I'm confused then. How many thermocouples do you have connected and to what channels are they connected too? Do you have both CJC's connected? Edited 29 Nov 2009 by Mickey

[ScottC 8]

If you have Ch. 3 configured for CJC and Eng. Units 1, then it should be reading from 0 to 850 in 0.1 degree C increments. There is no need to scale the value.

[ScottC 8]

Mickey, You can configure any channel of the NT4 to read the CJC temperature. You don't physically connect the CJC to the input terminals. It is done internally. When configured to read the CJC, the physical terminals are ignored for that channel. It's just a way to read the ambient temperature at the module. Usually it is done dynamically in the ladder program (switching back and forth between the CJC and physical input) so that you don't "waste" an input. Scott

[Mickey 71]

Thanks, I didn't know that.

[Pulsar2003 0]

Wow. Lots of attention here. Here is the set up: NT4 module is in the slot 5. Channel 0 has a J thermocouple. Channel 1-2-3 have nothing. There are two CJC as on the image supplied. Both have their upper screw as the positive one (as described on the label inside the cover) and the larger red terminal is there. I used AB's publication 1746-UM007C-EN-P. Page 6-3 there is a Dynamic Programming example. In this example you have a ladder logic that alows you to select the channel 2 from a CJC to a K thermocouple. N10:2 is: 0000 1001 0001 0001 N10:4 is: 0000 1001 0001 1111 The move command is used to change the configuration of the channel 2. In the publication they use slot 3 so the destination is O:3.2, me it's O:5.3. I will not scale this output. If I understand well it means that if I get a value of 25 thats means that the ambient temperature at the module is 25 C (if I'm set to be in Celsius). I can have that value move to a integer to show on a HMI so I can check what is the temperature inside the cabinet. If I understand well (again) the CJC reads temperature between 0 and 85C. Am I correct? WHAT I don't understand is why the light of channel 0 doesn't light up. The input works fine and the bit 12 is not on nor the 13-14-15. Bit 11 is obviously on because I get a reading. I think I have only 3 rungs, I wonder if it is not the length of the ladder that can cause that. All is in LAD2. Later on I will bring this PLC to the factory and will use it only to run the burner and watch how it goes. Anybody can tell me how I can set up so that I can change the value of the temperature? Most run at 300C. Let say I have to bring it up or down, how can I do it via a HMI. I know how to affect an Integer it's just how to I get the modified value to the PID? Thank you again gentlemen.

[Mickey 71]

What happens if you move the thermocouple to channel 1 and configure it the same as channel 0? Post your .RSS file if you can.

[Pulsar2003 0]

For the lights to go on I need to put 0 in the bit 9 and 10. I end up with the 10Hz filter. It's the only way I can get the lights on. I also turned on the channel 1 and 2 with no thermocouple hooked and the lights of these channels blink. So I know that there is something wrong and I can see it. I wanted only to have the 60Hz filter no to slow down the update of the channels. I made a few tests also. I changed the bit 8 from C to F and saw no changes. I toggled the bit 8 in the outputs O:5.0 and O:5.3. It didn't change the reading in the scaled output of the thermocouple in channel 0. I put the probe into iced water and it dropped to 1.075C (I used a Float to have the decimals on purpose) and next I put it into hot water and it rose to 68.785C which is representative of the situation. I heated up the module with it's door open to warm up the CJC, that didn't anything to the output. I want to make those test to see what happens to the PID output. That is how I learn and understand what happens. Through trial and error. Thank you.

[Pulsar2003 0]

I addes the .rss file of the ladder. There isn't much, it was just to see how I could make it work before having a larger project. Thermo_TEST.RSS Edited 5 Dec 2009 by Pulsar2003

[Mickey 71]

You said you have a 1746-NT4 but the card in the .RSS file you posted is configured for a 1746-INT4 which does not have a filter setting. What card do you have? See picture below if your card is a 1746-INT4. ( note description text) See link below for manual on the 1746-INT4 http://literature.rockwellautomation.com/i...um614_-en-p.pdf Edited 6 Dec 2009 by Mickey

[Pulsar2003 0]

You are correct Mickey. Probably when I typed in the module's model I missed the "I". On top of that there are only a few documents that shows off. I should have noticed that. I've studied the wrong document, at least I have gain allot of knowledge since. And you are right about the filters, there are non. So just the fact of putting a 1 in either 9 or 10 bit give a wrong configuration. You spotted that right away. Thanks allot.

[Mickey 71]

Your Welcome