A few years ago I was able to purchase a few pre-fabricated DS18b20 in a 1/8 NPT threaded probe.
Does anyone know where, in the United States, I can economically purchase more? I can't seem to find anyone making or selling them (probably not using the right key words in my google searches).
adwsystems:
I can't seem to find anyone making or selling them
You might try Alibaba. They have turned up on eBay but I have not seen them for a long time and the price was pretty steep when they did. I concluded the reasons for the above is that people use thermowells, so that is what I did.
Hi,
THESE "waterproof" sensors have a stainless steel tube that is 0.24 inches in diameter.
Some people use a 1/8 IPT to 1/4" copper tubing compression fitting and insert these sensors.
DISCLAIMER: Mentioned stuff from my own shop...
Nick_Pyner:
You might try Alibaba. They have turned up on eBay but I have not seen them for a long time and the price was pretty steep when they did. I concluded the reasons for the above is that people use thermowells, so that is what I did.
Alibaba did not turn up anyone in the US or economical from overseas.
I have pondered getting my own thermowell, but then I have to deal with mounting, insulating, and sealing the sensor.
I have also thought about getting one of the smooth bodied waterproof versions that are available and placing it in a threaded thermowell. But then there is an additional thermal junction, the corresponding thermal mass to change temperature before the sensor provides an equal reading, and since the waterproof version would require a larger diameter thermowell there is even more thermal mass.
adwsystems:
I have also thought about getting one of the smooth bodied waterproof versions that are available and placing it in a threaded thermowell. But then there is an additional thermal junction, the corresponding thermal mass to change temperature before the sensor provides an equal reading, and since the waterproof version would require a larger diameter thermowell there is even more thermal mass.
Sounds like lots of theory, and very little practice. Thermowells are commonly used in the industrial arena but, if they are as bad as you imply, they wouldn't be. And, if you are really serious about all this thermal mass stuff, you probably shouldn't be using a DS18B20.
The 7mm waterproof sensor shown above are hardly suitable wet in high pressure situations as there are no shoulders on it, thereby leaving you entirely reliant on the compression ring. This is probably not something you would want to walk too far away from. If you don't have any pressure, they are fine and, in that situation, I just put them in a standard retort bung.
I recall standard thermowells suitable for DS18B20s do not seem to be such a good proposition, and I found it simpler to make up my own.
Nick_Pyner:
Sounds like lots of theory, and very little practice. Thermowells are commonly used in the industrial arena but, if they are as bad as you imply, they wouldn't be. And, if you are really serious about all this thermal mass stuff, you probably shouldn't be using a DS18B20.
"Sounds like" would be correct. The thermowells and instruments I have used in "the industrial arena" are substantially smaller in diameter that what it would take to (a) make my own thermowell, that could (b) accept a probe 1/4" in diameter. The thermowells I have worked with have all been smaller than the 1/4" diameter making the sensing device even smaller. Since we are talking about circular items, the volume of material is increasing r-squared.
Nick_Pyner:
The 7mm waterproof sensor shown above are hardly suitable wet in high pressure situations as there are no shoulders on it, thereby leaving you entirely reliant on the compression ring. This is probably not something you would want to walk too far away from. If you don't have any pressure, they are fine and, in that situation, I just put them in a standard retort bung.
I have been pondering this idea, a little. How much pressure would you consider high? 10psig? 20, 30, 50psig? (beyond 30psig, other things will break anyway)
Nick_Pyner:
I recall standard thermowells suitable for DS18B20s do not seem to be such a good proposition, and I found it simpler to make up my own.
What do recall as being the issue? Can't find on that fits the device? Sealing?
adwsystems:
I have been pondering this idea, a little. How much pressure would you consider high? 10psig? 20, 30, 50psig? (beyond 30psig, other things will break anyway)
I'm afraid that, in my world, there are only two pressures - 0 kPa, and 800 kPa.
What do recall as being the issue? Can't find on that fits the device? Sealing?
I think nothing seemed satisfactory, and price had a lot to do with it, but probably most importantly, I had exactly the materials I needed in the garage - some 1/2" brass rod.
Nick_Pyner:
I'm afraid that, in my world, there are only two pressures - 0kPa, and 800 kPa.
hahaha. So what in kPa is high pressure? 800kPa is way high is my world. The system is toast by 250kPa.