Thermocouple Errors - Temperature Way Too High

[mac]

So, I purchased the company's 3' k-type thermocouple to use with the 6131 contoller:

http://www.lightobject.com/3ft-1M-K-typ ... -P113.aspx

The temperature creeps up overtime anywhere from 10 to 20 degrees above actual temperature. When it first comes on, the temperature is reasonably accurate, but over time it slowly creeps up until it is way too high. Is there a lot of temperature conduction on these? This TC has a threaded connector at the end. Would it work better fastened to a larger piece of metal?

The amount of error is not constant, so it is not feasible to use the temperature offset to correct it.

[richiem]

If the TC is not in direct contact with the medium being heated, be it air, water, other liquid, or whatever, then thermal delays between the controller temp sensing and the actual temp change of the medium can cause these errors -- an example: my son's old hot tub only heated the water and circulated it when the temp sensor, located outside the tub in piping, cooled off and turned the system on. The water in the tub was warmer than the water at the sensor, and the sensor would run the system until it's thermostat said stop, which heated the water in the tub even further. This loop delay would continue to raise the tub water temp and eventually trip the overtemp thermostat. The solution would have been to have a small circulation pump run constantly to keep the tub water flowing over the temp sensor, so that the temp sensor was always reading the actual tub water temperature. Of course, that's not what he did -- he got a different hot tub.... Just one way that these sorts of things can happen.

[mac]

If the TC is not in direct contact with the medium being heated, be it air, water, other liquid, or whatever, then thermal delays between the controller temp sensing and the actual temp change of the medium can cause these errors -- an example: my son's old hot tub only heated the water and circulated it when the temp sensor, located outside the tub in piping, cooled off and turned the system on. The water in the tub was warmer than the water at the sensor, and the sensor would run the system until it's thermostat said stop, which heated the water in the tub even further. This loop delay would continue to raise the tub water temp and eventually trip the overtemp thermostat. The solution would have been to have a small circulation pump run constantly to keep the tub water flowing over the temp sensor, so that the temp sensor was always reading the actual tub water temperature. Of course, that's not what he did -- he got a different hot tub.... Just one way that these sorts of things can happen.

That's really not my situation. The TC is in direct contact with the medium, which is air. The temperature creeps up over time. When everything is cold and first turned on, it is accurate, but after an hour or so, it reads about 15 degrees above the actual air temperature. At the present time, it is not controlling anything. It's just not reading accurately, which is the reason I was asking whether there is heat conduction from PID through the cable to the TC. One of the settings on the PID is an offset to compensation for conduction errors.

[mac]

I reconfirmed the situation this morning. If I turn off the unit and allow it to cool for a few minutes and then turn it on, the temperature reading is accurate. However, after about 10 minutes or so, the current temperature reading starts climbing even though the room temperature has not changed. My guess is the 6131 PID is defective and this is not a TC issue.

I have a Fluke temperature meter and will check the TC with that just to confirm.

[richiem]

Good plan to check the thermocouple. Depending on spec, the TC could be in error, but I wouldn't expect it to be off by as much as you're seeing -- may a degree or two, but not 15.

[mac]

I checked it with my Fluke meter and the TC seems fine. I also tried a k-type TC made by Fluke on the PID and have the same problem.

[Tech_Marco]

I did send you a email two days ago to send it back for refund. Check with your email, check your spammer!

We don't want to see such negative words in our forum and if you're doing again, sorry I have no choice but have your account suspended. You can criticize the product we're selling but you can't ruins our name and reputation!

Again, I did send you eamil two days ago after receiving your email that you couldn't get the controller working properly. I told you to send it back for refund. No reason for you to spend so much time on it.
I can post the email screen shoot with time stamp!

[Tech_Marco]

Just checked my email this morning (8:00AM PST), this guy sent three times email to 3 different accounts at the same time for requesting RMA#. Give me a break, I was still sleeping. Our office time is 10:00PM PST. Sending 3 emails at the same time to three emails account or total 9 emails and blaming on us not respoding, give me a break!

To Mac:
Mac, if you did again to bomb our mail box, I'll put your email to the blacklist. FYI, I'm receving hundreds emails dialy and it sure enough for me to handle.

In responding to your email, buyer pay for return shipping cost. It's clearly stated on my website agreement. But I won't charge restocking fee.

Marco

[mac]

Deleted

[Tech_Marco]

I deleted my last post here as I don't want to see the argument keep going on without ending...