I have the 2 thermocouples reading within 1 ohm of each other. I corrected the values in the sestos pid so they are both reading the same in a cup of water at 80 degrees c and 1 degree difference in a cup of water at 20 degrees.
Perfect in theory, but when I put the thermocouple probes on the same cassette I get completely different readings (50/30 for example)
Now this has to be cause by the way the wires are contacting the cassette right?
I am just pushing them in a small amount between the aluminium cassette and the heat mat making sure they are not near the wires in the heat mat.
(I have them wrapped in heat shrink because I noticed I was getting heat soak on the top cassette)
How is everyone else attaching the thermocouples and how accurate are your results?
First is with using such short TCs you might not be reading temps within your lsminate. First thing I'd try is getting some longer fine wire TCs.then place the end on the casette where your laminate will be and try again.
I make skis so have the thermocouple right in the centre of the cassette. The wires run lengthwise along the cassette stuck in place by heat resistant tape. They then turn 90 degrees and exit the side of the cassette beyond where the tips end.
I stick the thermocouple and wiring to the aluminium skin with the heat resistant tape then lay the heat blanket on top of that.
I only have one TC so can't comment on different readings. I have been meaning to get a TC reader and do some checking of what heat is like at the tip/tail when control is being done at the centre.
Thanks for the input falls.
If i didnt have 2 tc's I wouldn't know there was an issue here and I would be happily pressing thinking I know how hot it is when in reality it could be a long way off.
I tried several different way to attach TC to cassette. Most accurate end up being to use aluminum foil tape.
I use second controller with it TC to test temperature in different location on cassette
I have not failed. I've just found 10,000 ways that won't work.
Thomas A. Edison
Could you please do a test for me madrussian?
Boil a cup of water and put both probes in. Note the temperature.
Do the same with a cup of cold water. This tells you if your tcs are calibrated correctly or not.
Then tape them as you normally would, except both to the same cassette and see what you get.
Im wondering if more people are operating with inaccurate thermocouple readings without knowing which could lead to a whole host of problems
gozaimaas wrote:Could you please do a test for me madrussian?
Boil a cup of water and put both probes in. Note the temperature.
Do the same with a cup of cold water. This tells you if your tcs are calibrated correctly or not.
Then tape them as you normally would, except both to the same cassette and see what you get.
Im wondering if more people are operating with inaccurate thermocouple readings without knowing which could lead to a whole host of problems
1 test in cup of water and on the cassette is not the same
2 quality of TC is important
3 meet thermometer do not help to measure temperature correctly it fluctuate a lot make matters even more complicated and frustrating. (Look my Journal)
4 I don't need to do the testing I didn't build controller I bought the unit where TC already building
5 when I did testing on the cassette when TC play side-by-side using both showing same temperature
forgot to mention TC placed in the middle of the cassette on top of it right next to layup.about 2 inches in from the edge of the blanket . I use some insulation on the wire so it doesn't get pinched or fried
Last edited by MadRussian on Sun Nov 10, 2013 3:08 pm, edited 3 times in total.
I have not failed. I've just found 10,000 ways that won't work.
Thomas A. Edison
Richuk wrote:You appear to be adding pressure into the mix when running your tests.
Sorry you confused me there. What do you mean?
The pressure from the press pushing on the wire?
I also did it with the wire between the cassette/heat mat which would be softer. Same result.
I will try just taping the probe to the cassette and see what happens.
Goz. There is also some deal with grounded and non grounded thermocouples.
I don't know the exact specifics but if you are using 2 devices to measure separate TC's one could be assuming grounded and the other not.
Thinking about it I think I might have a little heat tape between the aluminium and the bare TC head. The aluminium sheet is grounded to the house ground also.
