1746-nt8

Hey all,

I have a question about configuring this analog card. I have tried to read the documentation, but never played with one before...

What is happening, is I am getting a constant blinking from all the LEDs on the card. It seems to startup, occasionally, with the lights steady, then eventually, they all start to blink. From what I am able to gather, the card will blink an LED on an open state of a TC. We went through, checked all the TCs for ground and open connections, they all seem to be fine.

Currently, I am using 4 inputs out of the 8, went through and started altering the output data table to disable all of them, then turn them on one at a time. Same result, regardless of how many of the 4 are on, or in any sequence. After talking to a local rep, they suggested that it must be an overflow of some sort, but honestly, nothing has changed in the program. Plus, this program has worked for about 1 1/2 years without any major issues.

Hopefully, someone has run into this issue before and can offer a suggestion. At this time, I would have to say the card is bad, but the company is reluctant to spend $800-$1100 for a new card, or even about $300 to have it repaired... Just trying to cover all the bases.

Thanks in advance.

Hoot

If you have the channels configured for a milivolt reading and you are reading a type J or K or.... thermocouple. This will also give you a blinking light. Same thing goes in the opposite direction.

I have also had trouble with that little teminal strip. Make sure it is seated. Make sure you have landed the wires in the correct 1.5mm opening. Double check the instalation of the CJCs

Final step would be to try and read the CJCs via on e of the channels as a verification step.

Hi Firebrd,

Thank you for responding. I am starting to lean towards the CJC sensors, but what's weird, is that it's faulting out all the channels, not just any one, or bank of 4. I did find an example program to put into the memory to test the CJC's, so that will be my next step... Did go through and verify that the terminal strip is seated, ohm'ed out the cjc's (about 14.5 ohms on both), and the wires for the TCs are all red and white (print calls for J type).

After doing this for a bit longer, and quite a bit of banghead I did figure out a few more things... The program does not have an integer file for redundancy, ie, to insert the parameters to the output file when on the first pass. It does seem to hold the parameters in the output file, but this is what I get in the input file table after the errors, all channels that are being used give me this....

15----->0
0 0 1 1 1 1 1 1 1 1 1 1 1 1 0 1
bit 0=enable/disable (enabled)
bit 1-4=type of TC (should be 0, for J, but what is show is 'invalid')
bit 5-6=data format (should be PID, but is setting to proportional counts)
bit 7-8=open circuit (this is set to disabled)
bit 9=temp (set to C in output, but showing F here...)
bit 10-11=channel filter (this is set to 250hz, output is 10hz)
bit 12=open-circuit error (on in this input file)
bit 13=Under-range error (on in this file)
bit 14=over-range error (off)
bit 15=channel error (off)

All the inputs are setup as follows, same format for each channel used...

1 0 0 0 0 0 1 0 1 1 0 0 0 0 0 1
bit 0=enabled
bit 1-4=input type (type J, all 0's)
bit 5-6=data format (setup for scaled with PID, verified in program...)
bit 7-8=open circuit (set to max on open circuit)
bit 9=temp, 0 signifies C
bit 10-11=filter freq (set for 10hz)
bit 12-14=unused
bit 15=input image type (set to data, instead of word)

I'll go through and verify that the connection is correct, and maybe go through and try some of the other settings, instead of J TC, use millivolt settings, etc... About the only thing that I haven't tried yet, just feels good to have someone verify a suspicion. Thanx again, Fire, will let ya know how it goes. :site:

Hoot

I have type J thermocouples and am using the input file

1000001010100001

Caution!!!!!!!!!!

Make sure you are using the manual and data structure for an NT8
There is a difference between it and the NT4

Tim


OOpppss!
I meant Output file, config file, whatever you want to call it.

by the way do you have a spare thermocouple in invintory just to double check with???

Hmm... very interesting...

Basically the same, but you are using scaled for engineering units, .1 and I am setting up for PID... that's gotta be it! The CJC's are rejecting the PID, since they are not addressed in the program... One way to find out. Gonna try now.

Fire, if this works, next time I'm in your neck of the woods, the rounds are on me beerchug

Thanx again!

Hoot

I just reread your post again after seeing my blunder.


Remeber that the configuration goes in the Output File

I don't know if yours was a typo like mine but I just wanted to make sure.

Hey again, Tim

I did try and alter to the engineering units, no luck.. but glad you told me it was a typo, otherwise I would really lose my mind This one's been a bugger for two days.

About ready to call it a day here at work, but will try the CJC program scheme tomorrow. After reading through the manual (for nt8 ), they finally said that all the sensors will blink if they are bad... Just need to verify the situation.

'preciate your help, and the first round is still on me

Hoot

Last attempt!!!

I use this data in my output file to read cabinet temperature via the CJCs.

1000001010111111


If this doesn't work I would say bad card or CJC

Most likely bad card.

Tim

Hey Tim,

Not that you're losing any sleep over this, but just to update...

I did try the shifting of data to status bits in the manual, addressed as needed, etc... and it's still faulting, but no idear why. Only had a few hours to play with it today...

I did diagnose originally as a bad card, but the company is starting to go south, so they don't want to dish out any more money than absolutely necessary. We did pull the CJC sensors today and test them, they are within .01 ohms of one another, so that should be okay... Originally tested at 14.5 ohms with a multimeter, but tried a bit more sensitive tester to verify any calibration, etc...

Called a local rep, they quoted me a price of about $120 for the 'terminal rebuild kit', which I guess is the female and 2 CJC sensors. Found the sensors to be a typical analog device part, so got 2 coming in tomorrow. After that, it's gotta be the card. Have to admit, though, learned a lot on this project

Now for my next question... how do you get money from accounting when the business is sour? At least the paychecks ain't bouncing

Hoot

question

Hoot, what the heck are CJC's? I must have missed something in your posts, you started out talking about TC or thermocouples and then this CJC thing crept into the thread. Seems you and firebird both know what they are, but I have been following your posts and have yet to get it myself. I feel kinda stupid, but just have to ask. I am not sure you need to replace your input module but then again, maybe.

Doh!

Never mind, I downloaded the manual and found the definition. Cold Junction Compensation, indeed! bonkhead

how do you get money from accounting when the business is sour? At least the paychecks ain't bouncing

Click to expand...

Buisness is the exact opposite on this end but we still don't get money. We launched 2 satelite plants this year and there are plans for another next. The kicker is that we are supporting these start ups so our entire engineering group is ordering all this nice equipment that we don't even get to put in our own plant. On the up side we can order all the duct tape and bailing wire we need to repair the equipment here. LOL

what the heck are CJC's?

Click to expand...

A thermocouple measures temperature at the junction of two disimilar metals. This happens on the buisness end of the thermocouple but it also happens at the terminal strip for the input card. Normally this is negligable but the CJC compensates for this variation at the terminal strip. I don't remember if the CJC is a thermocouple or RTD but it basically measures the temperature at the terminal strip and is used for calibration and compensation purposes. Since it does measure the temperature at the strip.....which is located on the TC card, I like to use it for cabinet temperature readings. PLCs are tough but temperature can still get'em.

Tim

Hey Randy and Fire

Well, bit happier today, it works. We started poking around the card, looking for anything at the board level, and found absolutely nothing. Yesterday, I had tested the original CJC's, and they were within .01 ohms of one another, but had 2 more come in just in case... We cheated, found that they were an Analog Devices part, and just ordered those

Put the new ones in, and voila, they worked great. After doing some research on the part, it's a trimmed circuit, so maybe, the slight bit of heat was throwing it off... At this point, my head still hurts, but the machine works, chalk it up to luck.

As for what is a CJC, the particular one that is being discussed is (quote from analog devices) "a two terminal monolithic integrated circuit temperature transducer that provides an output current proportional to absolute temperature".

Not sure if that helps, but Tim, thank you very much for your thoughts and suggestions. They did help tremendously in the troubleshooting process. Still owe ya that round beerchug

Hoot

Confusion

My only point of confusion on the CJC thing was the meaning of the letters. I know what cold junction compensation is and how it is accomplished most of the time. The sensor is usually a thermistor, by your definition, a monolithic device. The temperature at the terminal point is read and used to compensate for the temperature not being 32 Deg F as it needs to be for proper voltage/temperature relationship. The module in your case does the compensation and also linearizes the thermocouple input signal. Sure is a lot simpler than it used to be in the old days.

Slightly off topic, but nevertheless...

Recent releases of RSLogix allow you to use a dialog box to setup many analog cards such as this in the I/O configuration.

Not trying to insult anyone or anything, it is just that this gets overlooked and can be quite useful.