Thermowell-pt100 question

[Angie1]

I want to monitor the temperature in a HLT and mash tun and was thinking of using thermowells with the probe moved from one to the other. How effective is a thermowell with regard to lag and accuracy?

I was thinking of these two items pt100 and Indicator I presume apart from the thermowell to insert the probe that is all I need and the probe just connects via 3 wires to the indicator.

I only want to monitor the temperature which I do now by holding a digital probe thermometer in the respective vessels and would prefer just to be able to glance at a panel. I don't requiring any control. How accurate would the above equipment be and are there any other options. Thank you.

 

[Vossy1]

Class B PT100 are accurate to 0.3 of a degree IIRC and the display unit to 0.2 deg. You can do a single point calibration using an ice bath and then you should be pretty accurate.
As for lag times, I'm not sure, I think it would be trial and error, but I can't see it being too great.

I haven't fitted a PT100 to a fixed location in the mash tun is because I like to test several areas of the mash to check for pockets of differing temperatures, which typically happen when I have been lazy with the stirring.

 

[Aleman]

If all you want to do is monitor the temperature, A digital thermometer form Thermometers Direct would be best . . . using a stainless Gland (or even Brass) to mount it.

I'm mounting these in my Mash Tuns . . . just to keep an eye on temperature . . . as Vossy says the disadvantage of having it fixed in place is that you could well be measuring a cold or hot spot. . . . but then I have http://www.thermometersdirect.co.uk/aca ... meter.html to check consistency of temperature. . . . and the pH meter has a temperature sensor as it is an ATC model :lol:

 

[Angie1]

That's great, thanks Vossy.

I take it that the unit can be calibrated? I'll have to give them a call.

I take your point regarding the variable temp in the tun, I will use it as guide as to when strike temp is reached when preheating with hotter than mash temp water, and will still check with my hand held which is extremely Acurate (£9 ebay) after the dough in.

Aleman, my thinking is that I can use one probe in any vessel I want rather than having multiple thermometers of dubious accuracy, plus I can insert the reference thermometer into a thermowell to check or calibrate

 

[Lurch]

Um. Yeah.
There is an awful lot of disinformation in the industry regarding sensor accuracy.
PRTD accuracy refers to the base elements, adding wire and housing means all bets are off. Which is why calibration is necessary.
Quoted (absolute) accuracy of less than 1C is a little optimistic for most low cost units.
Lag is a function of mass. There are no shortcuts. Therefore a slim probe and well reduces this.
Thermal gradients can be a problem, which means the probe should insert as far as practical - certainly 50mm with a well.