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RTD's and thermocouples

Posted: Sun Oct 24, 2010 8:12 pm
by Manback
So, I've been ringing around and googling everywhere (unfortunately nowhere convenient to go in ChCh)

I want a temp sensor to go to a digital screen for my still. Can anyone tell me - what is the minimum probe length that would be physically ffeasible for each of these two types of sensors?

As in - it's going into 1" tube, so the shorter the better.. obviously, we can add a little extension, but we'd rather not..

Anyone got info?


Cheers guys

Re: RTD's and thermocouples

Posted: Mon Oct 25, 2010 7:22 am
by rednose
If you want to control a switch or heat source you would need a thermocouple controller, if you only want to read the temp you can go for a K-type instrument.

The shortes probe in K-type I have bought is this (2 cm):

http://cgi.ebay.com/1-K-type-Thermocoup ... 1e5b3cff3c" onclick="window.open(this.href);return false;" rel="nofollow

There exist a very cheap one but the probe is losen in a srew and doesn't seal, you would need to soft solder it to seal (won't buy that one).

joe

Re: RTD's and thermocouples

Posted: Mon Oct 25, 2010 4:34 pm
by jdpete
You could try auberins.com

Jeff

Re: RTDs and thermocouples

Posted: Mon Oct 25, 2010 10:58 pm
by hoody
Quite a few on Trade-me. I've got a cheap one in the post at the moment. Dont think it is exactly what I am after but for $8 I cant go to wrong. There is a few probe type one's on there varying from $10- $120.
I tried Dick Smiths on the weekend too but they just looked at me funny (that shop sure aint what it used to be!)

Hoody

Re: RTDs and thermocouples

Posted: Mon Oct 25, 2010 10:58 pm
by hoody
Quite a few on Trade-me. I've got a cheap one in the post at the moment. Dont think it is exactly what I am after but for $8 I cant go to wrong. There is a few probe type one's on there varying from $10- $120.
I tried Dick Smiths on the weekend too but they just looked at me funny (that shop sure aint what it used to be!)

Hoody

Re: RTD's and thermocouples

Posted: Mon Oct 25, 2010 11:19 pm
by olddog
hoody wrote:I tried Dick Smiths on the weekend too but they just looked at me funny (that shop sure aint what it used to be!)
I managed a couple of their stores when Dick owned them, now their owned by Woolworths that's when they went downhill. :evil:


OD

Re: RTD's and thermocouples

Posted: Mon Oct 25, 2010 11:28 pm
by olddog
Try Jaycar NZ, they have got thermocouple's


OD

Re: RTD's and thermocouples

Posted: Wed Oct 27, 2010 12:18 am
by Manback
Ended up having to go through InTech to get one with the fixed thread fitting etc.. man, display units aren't cheap!

Shortest probe possible was 10xDiameter, so 30mm with a 3mm diameter probe.. perfect!

Re: RTD's and thermocouples

Posted: Wed Oct 27, 2010 12:38 am
by Samohon
I got 2 K-type probes when I bought my thermometer, but I could'nt tell what the probe material was made from...
Bought a new SS 30mm K-type probe from RS Components for £8.00 ($11US)...
I then hard soldered it into a 10mm x 40mm peice of copper pipe that slots inside a peice of 12.5mm copper with a wrap or 2 of ptfe...
Worked out ok...

Us here are HD are a very inventive lot... In most cases, there's a way round the problem... :D

Re: RTD's and thermocouples

Posted: Wed Oct 27, 2010 7:22 am
by Caprimulgus
Wondering what you plug those thing into? What are those display units called? Any pic or URL?

Re: RTD's and thermocouples

Posted: Wed Oct 27, 2010 2:16 pm
by Manback
There are milllions of options when it comes to the process indicator - depending on what you want - number of inputs, size, alarm etc..


I'm going to InTech in about 30 mins. I'll let ya know. The thermocouple has a 1/4" BSP fixed thread btw