metalresearcher
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How to get type S thermocouple readout ?
For temperature measuring (e.g. metal melting) I use a Type K and Type S (Pt / PtRh 90/10) thermocouple. The type S can be hotter (1400-1500 C) than
K (1100-1200 C shortly) or longer stay in 1100-1200C environment.
But the only readout for me is a mV multimeter and a table. There are lots of type K readouts (including my own multimeter) but I cannot find type S
readouts.
Does anybody know where I can get electronic type S readouts ?
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Halcyon
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*EDITx2* If you're looking mr places to buy meters that read s-type TCs, my apologies. Instrumentation places should sell them but they'll be
expensive. You should just be able to find some at electronics shops.
*EDIT* Disregard that, check here for S-type values, degrees Celcius.
http://www.pyromation.com/downloads/data/emfs_c.pdf
Values for other types of thermocouples, and values for degrees farenheit may be found here (bottom section):
http://www.temperatures.com/tctables.html
[Edited on 17-10-2010 by Halcyon]
[Edited on 17-10-2010 by Halcyon]
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Magpie
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Look at the specs on this:
http://cgi.ebay.com/PID-Temperature-Controller-SSR-Kiln-Furn...
You will not only be able to read S thermocouples, but many other types too. Also you will get a K type TC, and a PID controller to boot. I have
bought 2 of these.
[Edited on 18-10-2010 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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crazyboy
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How are those used to regulate the temperature of, say, a hot plate? I understand the thermocouple and how it is attached but how is the hot plate
integrated into this?
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smuv
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The pid has an output which controls a relay. It cycles the load on and off based upon the temperature reading of the thermocouple.
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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Magpie
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Controlling a hotplate is not ordinarily the intent. But they are excellent for oil baths and furnaces.
To use it with a hotplate you would have to somehow fix the TC end to the heated surface, attempting to get good heat transfer, and hoping that the
point you are measuring is representative of the hotplate as a whole. This would give you some form of control, but how useful it would be I don't
know. I've used surface thermometers on hotplates before - they were only marginally successful.
The single most important condition for a successful synthesis is good mixing - Nicodem
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smuv
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whats the point of controlling the temperature of the plate? The temperature of the plate usually varies greatly from what you are heating. Using a
PID to regulate a oil bath as magpie recommended makes more sense, but even then its not optimal.
I think dimmers are really good at regulating hotplates especially for distillations (using oil or water baths). The reason being is even a good PID
is only capable of providing 100% or 0% power to the hotplate. What this causes is a temperature that is within a few degrees above or below what you
want but is only at the temperature you want transiently. With a dimmer controlled hotplate in conjunction with a thermometer, after you initially
get the system dialed in, you can keep the temperature steadily exactly where you want it. This setup is really nice for distillations if you lack a
heating mantle/variac.
I honestly cannot think of one application where a pid/thermocouple/relay setup would outperform a dimmer.
[Edited on 10-18-2010 by smuv]
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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crazyboy
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Quote: Originally posted by Magpie  | Controlling a hotplate is not ordinarily the intent. But they are excellent for oil baths and furnaces.
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Sorry, I meant an oil or sand bath atop a hot plate. My hot plate has the tendency to get very hot and if I want to keep a mixture below a reflux I
have to continuously watch it and turn it on and off.
If I were to purchase a PID controller with a K thermocouple would I need to buy anything else to use it as a temperature controller? That is how
exactly is is it used? I know you set the target temperature on the controller, put the thermocouple into the mixture or oil bath and attach the
thermocouple to the controller. But how do I connect the hotplate to the controller so it can turn it on and off? Is it complicated, am I missing
something?
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Halcyon
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| Quote: Originally posted by smuv | | I honestly cannot think of one application where a pid/thermocouple/relay setup would outperform a dimmer. |
Can't you?
No-one said the thermocouple had to be inside the hotplate. Stick it in your distillation head and it'll control nicely.
And decent (not to say digital-output controllers aren't) PID controllers can drive SSRs to provide an analogue output.
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metalresearcher
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Does it mean that I can connect this device on the 220V mains , plug in a K or S thermocouple and plug in the Kanthal furnace which I want to control
?
There are no specs on the page .
EDIT:
This one looks even better.
[Edited on 2010-10-18 by metalresearcher]
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Magpie
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This is what I find on the page:
Specifications:
Power requirement: DC90-360V; AC 90-260V; 2W
Display Fahrenheit / Celsius
Accuracy 0.2%FS
Relay Spec 3A / 220VAC
SSR Voltage Open circuit: 8V; Close circuit: 40mA
Compatible Thermocouple
Thermo Resistor
T, R J, B, S, K, E, WRe3-WRe25
Pt100, Cu50
Operating Temperature 32 - 120 deg F / 0 - 50 Deg C.
Dimension: 48mm x 48mm x 82mm; DIN 1/16
If you want to use this as just a TC readout then all you need to do is power it up. If you want to use it as a controller then you need a relay. I
used a SSR ($10) in a setup like this:
[Edited on 18-10-2010 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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S.C. Wack
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I suggest Watlow for ebay PID's if for no other reason than they have a website with full documentation and the ability to look up the full specs
yourself like supported thermocouple types, if the full model number is given in the listing. And because their PID's and SSR's are known to be
reliable, professional units.
(That said, I also have a TET612 almost identical to the auction item.)
Simple dimmers get too hot and are undesirable for high wattage. There are good solid state devices but not at Walmart; of course Glas-Col controls
are tiny but the damn things can't be taken apart easily so that I can see what's inside. But digital readout, rampable PID's with precise control
always win over knobs anyways.
Fluke 53 II and 54 II thermometers will take S-type thermocouples if you happen to have one laying around.
[Edited on 18-10-2010 by S.C. Wack]
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