Bi-Metal Thermowell Idea

CothermanDistilling

I think I want to try using a half copper and half stainless thermowell, the copper on the probe end will transmit the temperature through to the probe, but the stainless will restrict the transmission from the outside metal, giving the best performance.

Maybe 3/16" copper tube soldered/brazed/welded to a 1/4" thermowell tube?

grim

Direct contact sensors, RTD or Thermocouple.

Sanitary for product contact and thread or sanitary for cooling and heating fluids. If you find a deal on a probe, you an even use compression (metal on metal).

If you are looking to cut response time, why mess around with making a thermowell?

You can easily buy a fast-response copper tip, stainless body direct contact sensor from most of the major vendors for under $100.

CothermanDistilling

Thanks for pointing out how cheap I am, my thermistors are $3.42 ;-) and can be removed in a few seconds (I have to use thermistors with the BCS, until I can convince them to go RTD)

EPCOS B57500M103A5 NTC THERMISTOR @ Newark

and for $9.90, some smaller ones:

AMPHENOL ADVANCED SENSORS MA100GG103C NTC THERMISTOR @ Newark

for what may be considered a direct contact, I did get these for $4.33, (now $7.50)

USP10972 THERMISTOR PROBE NTC 10K OHM 1% @ Digi-Key

they are a bit short, and the leads don't have a stain-relief, so they fail, even tried silicone/heat-shrink, etc...

us sensor will make you anything you want custom, but $$$$$

CothermanDistilling

OK, googling, I found an omega one 4" long...

General Purpose Thermistor Probes Stainless Steel Sheath @ OMEGA

but then I remembered why I like my thermowells... I can pull the probe out and the hole is still sealed... great for smaller homebrew system, not quite as needed on larger stationary system. I can also do quick disconnects, but never found any that I really liked at my frugal price point

Manofconstantsorrow

@CothermanDistilling said: but then I remembered why I like my thermowells... I can pull the probe out and the hole is still sealed... great for smaller homebrew system, not quite as needed on larger stationary system. I can also do quick disconnects, but never found any that I really liked at my frugal price point

You can also accomplish this by means of a plug with a compression fitting. I have always seen issues with thermistors and find them unreliable for precision temp measurement, the theory is nice but there are too many factors that can affect how they read, pressure, wire size and length, ETC. This is not to say that RTD's don't have issues too but I find to be more reliable and they tend to last longer then thermocouples and thermistors,IMHO

CothermanDistilling

this right here is one of the direct contact probes that had the wires break, so I hollowed out the potting compound:

what you see is my thermistor pushed in (smaller siamese wires) and the SD probe is pushed in behind it to keep firm contact between the thermistor and the tip of the probe, the probe is very, very thin walled (better for both transmitting vapor temp and rejecting column temp).