Controller showing wrong ambient temp

[Babs]

Noticed last night ambient temp showing on cotroller was abot 16deg C above actual temp. Kiln was standig with lid open for the day and temp was nowhee near what was showing, is this a sign of  worse things to come....

Haven't opened kiln yet to see whatthe target temp inaccuracy may have been

Cone packs not in as I had no fears and when notuced, cone packs 200 m away in pottery shed, kiln on verandah...

[Dick White]

This is normal for some kilns, particularly L&L with the protective tubes over the thermocouples. The controller is set to read higher than actual in the kiln to account for the insulating value and thermal lag of the porcelain tube. Cone packs in multiple firings can tell you whether the kiln is actually over or under firing, and then you go into the controller settings to adjust the thermocouple offset until the controller produces a correct outcome in the kiln using whatever slight shift you have fooled it with.

[Babs]

2 hours ago, Dick White said:

This is normal for some kilns, particularly L&L with the protective tubes over the thermocouples. The controller is set to read higher than actual in the kiln to account for the insulating value and thermal lag of the porcelain tube. Cone packs in multiple firings can tell you whether the kiln is actually over or under firing, and then you go into the controller settings to adjust the thermocouple offset until the controller produces a correct outcome in the kiln using whatever slight shift you have fooled it with.

Thanks Dick. Used the kiln for a number of years now and this much higher initial reading was a new thing.

Next firing will have packs in again, and yes thermocouple has porcelain sheath 

[Mark C.]

My guess and its really a long shot-

it's the Timbuktoo factor

[Babs]

On 2/24/2021 at 3:25 AM, Mark C. said:

My guess and its really a long shot-

it's the Timbuktoo factor

Well that is where I hail from so I'll just toddle down to my very accessible supply shop!

My next thought is v hotspell here, frequent empty, load scenario over past few weeks... need to leave kiln a while before checking there is a prob, but that's my denial factor creeping in, common in Timbuktoo, then turn on the vigilancewith cone packs everywhere and see...maybe.

[neilestrick]

If the thermocouple is in a protection tube, then an offset is typically set in the controller to compensate for the insulating factor of the tube. That offset makes it read higher than room temp when the kiln is completely cool. If you don't normally let your kiln sit empty for a few days between firings, or the there are room temperature fluctuations due to weather,  etc, then it may seem like it's reading oddly. Ultimately that doesn't matter if it's firing correctly, though. So hold off on changing anything until you fire, preferably with cones.

[Babs]

Thanks Neil. Looked at user guide and dont see a mention of an offset dial/button, scrww.

Controller is a Stafford ST316A, BRITISH breed,  Iguess!

Waiiting at the mo for a kiln to cool down and then there will be a space for a numver of days before next firing.

Freaking a little because of remote factor.

[Bill Kielb]

I believe that controller uses a type R thermocouple which have a long comparative life but also can drift as the material changes. I would suggest removing it from the sheath and checking for corrosion that may be insulating it from the end of the protective sheath and of course making sure all connections are clean and tight. My copy of your manual is eighteen pages and I did not find an offset provision. 

The unusual high early reading though could be stored heat and just a tcouple no longer contacting the end of the tube reasonably. The disparity can show up early because conduction is a primary the main source of energy but later as red heat is achieved radiation heats the thermocouple so whether it is touching or not has less influence on its sensing.

here’s to hoping it’s just house cleaning and repositioning!