1734-IT2I Thermocouple Input

[janner_10]

First time using a point IO TC Input module.

I am using a R Type TC.

Config is set to Celcius & Type R obviously.

However both TCs are showing a reading of -50 or so.

Both TCs are wired directly into terms 4&5 and 6&7 as per the manual.

I note I do not have the 1734-RTBCJC terminal block, Am I correct in assuming this is essential hence my erroneous readings?

 

[AustralIan]

I have never used one without the thermocouple base, so I cannot comment if it will work or not.

However, I would point out that the 12 point base jumpers pins 4,5,8&9 and jumpers pins 6,7,10&11. You didn't say which one you were using (8 point or 12 point).

 

[janner_10]

I'm using the 8 Point, I've ordered the TC base now. It can't really be anything else in my eyes.

 

[Highland Controls]

Polarity backwards?

 

[Highland Controls]

Red=-, black=+.

 

[Dravik]

I've never used one w/out the Cold Junction before...
But we've had those kind of readings when our CJs failed...

 

[MaReKA]

I've used the 1734-IT2I module only with the recomended (Page 16) 1734-RTBCJC terminal block but according to the manual you can disable the cold junction linearization and specify a fixed Cold Junction Offset. I would order the terminal block and, while waiting for it to arrive, give this a try and calibrate against some known temperatures.

Have a look at the setup parameters yourself:
http://literature.rockwellautomatio...ture/documents/um/1734-um004_-en-e.pdf#page34

 

[Ken Roach]

Cold junction compensation is essential to all thermocouple measurement systems. You literally cannot know the temperature at the hot junction if you don't know the temperature at the cold junction.

You *could* use a fixed offset and measure the temperature at the base, but the only real solution is to buy the correct CJC terminal block.

 

[janner_10]

Good advice chaps, I have ordered to CJC block now. £30 from Routeco, its a no brainer.

I'm not commissioning it until after Xmas, but glad I powered it up in the office before-hand (I break up on Friday so have to look somewhat busy this week)

Thanks for all the replies on the subject.

 

[NetNathan]

From Publication 1734-UM004F-EN-E...
http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1734-um004_-en-e.pdf


Cold Junction Compensation
(1734-IT2I module)
When using thermocouples, cold junction compensation is required at the
termination of the thermocouple wire. Accomplish a cold junction in the
following ways:
• Enter an estimated temperature.
• Use a 1734-TBCJC mounting base (recommended).
• Use external cold junction compensators.
Entering an estimated temperature is the least accurate way for CJC
compensation. Using the compensation built-into the 1734-TBCJC provides
the easiest and most accurate way.

An open CJC causes the CJC input to point to the maximum temperature
value for the selected input type. This causes an alarm to be set. Once the
alarm is issued, it remains active as long as the input signal is faulted (above
maximum).


Also...a note..
https://rockwellautomation.custhelp.com/ci/fattach/get/113141/