May have bought the wrong PT100...

[jdgabbard]

Not sure if I have purchased the right equipment after having examined it a bit further last night.

I recently purchased a couple of PT100 RTDs and some Thermowells from fleebay. Links are provided below. The RTDs have come in, but not the Thermowells. But after having looked at them I think I clicked "buy now" too quick.

The thread size for the probe says it is an M8 1.25, and the thermowell is a 1/2" NPT. So I'm pretty certain I'm going to need an adapter if they make them. Anyone else run into this problem?

The RTDs:
http://www.ebay.com/itm/RTD-Pt100-T...687?pt=LH_DefaultDomain_0&hash=item418f89b047

The Thermowells:
http://www.ebay.com/itm/Stainless-S...661?pt=LH_DefaultDomain_2&hash=item3a90d2d62d

 

[Mojzis]

I bought these: http://www.ebay.com/itm/RTD-Pt100-o...758?pt=LH_DefaultDomain_0&hash=item35cb28ed6e

I've been happy with them. I also noticed the cheaper RTD's were an unusual size.

 

[jdgabbard]

Yeah, I saw those after a quick search, but I hate to have to order another set of RTDs if I might possibly be able to find an adapter, or bushing if you will... I think I will head down to the local (read: rural) hardware store during my lunch hour to see if I can see anything that may be of use. I don't think the RTDs are too picky about being pushed all the way to the end of the thermowell from what I've seen on the net. But I could be wrong, and have been before. I could always find a use for these if I have to order some more. But I REALLY hate waiting on shipping from china, not to mention I'm too much of a tight-wad to confortably shell out the price the US sellers are asking.

But then again, I should have remembered the age old rule: Measure twice - order once, measure once - order twice......

 

[augiedoggy]

The 1/2" npt probes are designed to be used with or without a thermowell... I have some of the m8 ones and I just drilled a smaller hole in my pot to mount them with an oring to seal them...
unfortunately you ordered the wrong ones you can make adapters by drilling and mounting them in a plug or just use some rubber facuet washers like I did in one of my applications to hold them in place

 

[jdgabbard]

Yeah, I figured I might as well order the 1/2" variant because they're waterproof. And I did, shortly after my last post. I'll figure out some way of using these. I'm going to need to figure out some type of adapter plug. From what I can tell, the m8 1.25 is similar to a 5/16 nps? If that is the case I might be able to find a 5/16 adapter, and turn it down to fit inside a 1/2" adapter and solder it in. But I'm going to have to see what I can find at the hardware store. You'd think that someone out there would have thought about this and marketed a solution...

 

[Ravenshead]

You're fine. I've been using the exact same setup for years. You just slide the RTD into the thermowell without bothering with the threads. The response time isn't as fast as it would be if you had mounted the RTD directly to the pot but it's good enough. Plus, with a thermowell, when your RTD fails (they all do eventually) you don't have to use a waterproof one to replace it. You can also move your RTD to another thermowell installed pot if you need to.

 

[jdgabbard]

Raven, that's a good point. But I already bought the other two. So like I said, I'm sure I can find some use for these. I found an adapter that the nut can barely fit into. I think I'm going to break out the muriatic acid and see if I can solder it into it. If it works, it should be interchangable.

 

[Ravenshead]

You don't really even need the adapter. You can just slide the RTD in the thermowell and leave it alone. It won't come out unless you're brewing on a slope or using it on a vertically mounted RIMS tube with the sensor on the bottom.

 

[augiedoggy]

You don't really even need the adapter. You can just slide the RTD in the thermowell and leave it alone. It won't come out unless you're brewing on a slope or using it on a vertically mounted RIMS tube with the sensor on the bottom.

yes this is why I mentioned using an oring or rubber washer to hold the probe in place... your supposed to use thremal grease inside the thermowell and stick the probe inside that to you get correct temp transfer without the dead space to effect readings...
I spend the $20 on these and havent looked back...
http://www.ebay.com/itm/RTD-PT100-T...963?pt=LH_DefaultDomain_2&hash=item3a9ebb24db

They are easy to unplug the cables from so I can remove and clean my kettles without the cables catching on things and damaging the wires...I ruined an m8 style one by catching the cable on a doorknob and that was the last straw with the cables.

 

[Ravenshead]

yes this is why I mentioned using an oring or rubber washer to hold the probe in place... your supposed to use thremal grease inside the thermowell and stick the probe inside that to you get correct temp transfer without the dead space to effect readings...
I spend the $20 on these and havent looked back...
http://www.ebay.com/itm/RTD-PT100-T...963?pt=LH_DefaultDomain_2&hash=item3a9ebb24db

They are easy to unplug the cables from so I can remove and clean my kettles without the cables catching on things and damaging the wires...I ruined an m8 style one by catching the cable on a doorknob and that was the last straw with the cables.

Those are pretty sweet and I'll probably go there eventually but they aren't necessary. I've just been using the bare RTDs without bothering with thermal-grease or o-rings or anything else for years. The response times probably aren't as good as they can be but they're good enough for brewing.