Thermocouples.

[rosinante]

Type R and S go to higher temps but are significantly more expensive , I worked for a heat treatment company and in the hardening furnaces we used duplex type S TCS , incidentally each thermocouple contained 14 grams of platinum ,rhodium , high scrap value , changed 3 monthly ,
Chris

 

[julianthegypsy]

Aren't thermocouples calibrated with freezing water and boiling water ? 0 degrees and 100 degrees ?

They were in O level physics!

 

[sako243]

Something that hasn't been mentioned here which is rather fundamental and important to thermocouple work.

Their response is non-linear and they have polynomials that describe their behaviour with respect to temperature. For anyone wanting to do their own control electronics you'll probably be better off getting hold of an IC that does the calculation / interpolations for you (unless you fancy writing your own code). E.g. a bunch of Analog Devices chips that will interface to a thermocouple and then either output a linear analogue voltage or have a digital interface that you can interrogate for the temperature:
https://www.analog.com/en/parametricsearch/11146#/

 

[julianthegypsy]

I bought a cheap pyrometer off the bay for my kiln, but the probes were useless over about 400 degrees, so I replaced them with more expensive ones, also off evilbay, but more expensive and obviously better quality. Instead of inserting them, I leave them screwed to the kiln wall. I cook clay up to 1000 degrees no problem. The kiln is a stainless steel box lined with 50mm of foundry blanket, fired with a weed burner, reverse flow. Works a treat.

 

[daleyd]

Something that hasn't been mentioned here which is rather fundamental and important to thermocouple work.

Their response is non-linear and they have polynomials that describe their behaviour with respect to temperature. For anyone wanting to do their own control electronics you'll probably be better off getting hold of an IC that does the calculation / interpolations for you (unless you fancy writing your own code). E.g. a bunch of Analog Devices chips that will interface to a thermocouple and then either output a linear analogue voltage or have a digital interface that you can interrogate for the temperature:
https://www.analog.com/en/parametricsearch/11146#/

Post 11.

 

[Shox Dr]

Can you get a timer that drops the temp over a given time

 

[daleyd]

Can you get a timer that drops the temp over a given time

I don’t know if the cheap pod controllers have a programmer function built in, the ones we produce do so you can profile a temperature, ie ramp up at a set rate, hold, wait for certain conditions then ramp down at a set rate etc

 

[Shox Dr]

What sort of cost are these dodads

 

[daleyd]

What sort of cost are these dodads

The eBay specials are are cheap as chips, but as I say I’m not sure if they can do a program profile. Ours are a few hundred quid upwards but are proper industrial equipment, with options for comms, extra IO modules etc.

 

[Kayos]

Can you get a timer that drops the temp over a given time

I found a cheap ish one that did that, you need a degree in gibberish to program it though

 

[Shox Dr]

So the pids just hold temp for a set time.

 

[Kayos]

The cheap ones hold the temp, they use an electronic relay to pulse the heater. I found one with ramp up, hold and ramp down. More luck than by design

 

[daleyd]

So the pids just hold temp for a set time.

Give me a shout if you have a need for one, I may have something lying around