Hi Guys, this is one of my favorite topics. Please be patient with me.
I came into this industry from the engineering department at a ceramic furnace manufacturer. I have explored many of the ovens on the market and looked at their components as well as their quality and am glad I work where I work now. But let's put aside where I work.
If I could give you some piece of advice that would make you all more happy with any furnace you own it would be this,"Quit obsessing about your calibration so much."
It is important, but what is more important is understanding how your furnace functions. Your temperature is affected by multiple components. One of which is your thermocouple or more aptly put, "thermometer". This device merely reads the temperature and reports back to the oven what it sees. BY changing your calibration you are affectively changing the reading, and not necessarily addressing the real issue. So what to check then:
1. The heating element!!!! This is the cause of many issues associated with temperature change. In fact it does not make sense to calibrate an old oven with a crap heating element because the heating element's condition can cause temperature distortions. This is caused by an output change in one or more part of the element, thus heat will be more intense in one area, less intense in another area.
2. Although not all ovens are equally affected, inadequate power supply can cause problems. If you are not getting enough power or have equipment competing for power then this can cause temperature drops during programs.
3. Poor maintenance, keeping the oven clean and dry is important. If you de-gas in your oven then accumulated contamination can cause temperature problems with multiple components, either the thermocouple, heating element or insulation etc.
4. Now let's look at the thermocouple. Is it broken from moving or something hitting it? If the wires from the thermocouple cross at any point other than the tip, than a secondary temperature reading point is created, thus there is no way an accurate reading can ever be established.
5. Your electronics, control circuitry, relays are probably beyond your control. I wouldn't bother going there, other than to say think of where the wire that connects your thermocouple to your mainboard has to travel.
Laboratory calibration methodologies are meant as band aids or as consumable products. They are not true calibrations. The only true calibration happens at the factory or dealer where your furnace is serviced. There is a specific protocol and specialized instrumentation that must be used.
So, the overall truth of the matter is; the better quality your equipment, the better you take of it, the less you should see anomalies. If you suspect you have a "calibration" issue, meaning a temperature issue, then check your components. Short of that, the best you can do is calibrate to you (your eye) by firing a shade tab in your oven and offsetting the programs in your oven using the global calibration offset most ovens are equipped with.
Good luck. If you have any questions, I'll be happy to answer them.
i found Als oven.... Notice the name at the lower front of her dress...
