My Sherwood Wisdom will track and log various parameters every 15 seconds. When I look at the deep dive profiles on my wisdom, the coldest temp registered usually 15-18 minutes into the dive - sometimes even when I am on my up to warmer and shallower water.
For example on my last dive, the air temp was 73 degrees, it took 5 minutes to reach 53 degrees and another 12 minutes to chill to the minimum bottom temp of 44 degrees at 127 ft.
Regardless of the thermometer and location used there will always be some lag. There is a lot of difference in heat working between 73 degrees and 44 degrees to cool the thermometer but not nearly as much difference between 53 degrees and 44 degrees, so the change at the low end of the scale will take much longer to occur. The last few degrees can eb expected to take the most time.
I would hope that Uwatec uses a temp sensor that is directly exposed to the water outside the console and is insulated from the rest of the console/computer. If it can be downloaded to display temps and depths in increments during the dive, you can check to see how much lag exists.
I suspect though that Uwatec uses the same basic design as Sherwood does with the Wisdom the same basic limitations. However if Uwated uses broad ranges of temps to adjust the dive profile, then it still works. If anything below, for example, 55 degrees is considered cold, then you would still get your NDL limits adjusted within 5 minutes of entering the water and the system still provides some measure of additional saftey for cold water dives.
