Down the page is indicated "*Temperature range and stability vary depending on bath volume, surface area, insulation and type of fluid.
Notes: Performance specifications determined at ambient temperature of 20ºC/68ºF."
I understand "temperature range" = "temperature precision".
Should we also have to conclude that Polyscience machine cannot assess the quantity of water contained in a container, the ambient temperature...and therefore Polyscience can't guaranty temperature precision?
I have a Polyscience immersion circulator. It usually is used in a 20 Liter All-Clad brand stock pot. I have the stock pot wrapped with about 1/2" (12MM) bubble type aluminized insulation. The top is covered with a 1/4"( 8mm) plexiglass sheet that I cut out to fit tightly around the Polyscience circulator in order to reduce evaporation water loss. I have run this unit for at least 24 hours without more than 1/2" (12mm) water level loss.
The Polyscience circulator easily maintains 90C in this water bath. ( the highest I have used so far.)
I have tested the temperature variations in the water bath using a Thermoworks Microtherma 2 thermometer and find the temperatures within .5C in all locations.
I think that my water bath is probably larger than is typical but my results seem to confirm the capability and accuracy of the Polyscience immersion circulator. I do feel the larger mass of water makes the whole system much more stable. For example dropping a 2# (approx 1 kilo) frozen pot roast into the bath never drops the temperature more than .5C and that is for just a few minutes.
The unit is so dependable that I never hesitate even the longest (up to 48 hours) cook times.
I hope my observations are helpful.